Seminars

Journal club

Scheduled talks:

Thomas Hahn

Title: One-Way Hashing Method with Finite Resources

Abstract: The one-way hashing method refers to a well-known entanglement distillation protocol that can be used to transform multiple copies of a bipartite state into high fidelity Bell pairs, using only local operations and classical communication. While it is known that this protocol is very effective at distilling entanglement from large-scale systems, previous results indicated that the one-way hashing method may not be useful when the number of initial copies is small. For this reason, the protocol has not yet been realized by any experimental setup. By leveraging properties of the Hartley entropy, we provide significantly improved analytical lower bounds on this protocol's distillation rate, as well as numerical simulations, which demonstrate that entanglement can be distilled via the one-way hashing method at a higher rate and using fewer initial copies than previously expected. These results show that the one-way hashing method is not only of interest for future large-scale quantum networks; it is also a viable option for distilling entanglement on state-of-the-art quantum technologies.

Sergey Hazanov

Title: High Interharmonic Generation from Isolated Bound States

Abstract: High harmonic generation (HHG) is a nonlinear process in which systems driven by intense laser emit integer harmonics of the driving field. Here we report that the strong nonlinear response of systems with isolated bound states split the HHG spectrum into non-harmonic Mollow-type triplets that reveal the internal electronic dynamics. We identify the conditions required to observe these phenomena and propose potential experimental systems that could enable their detection. Our findings offer new insights into the fundamental physics of HHG and may have applications in high-harmonic spectroscopy, X-ray physics and study of ultrafast dynamics.

High-dimensional quantum information processing using spatially entangled photons

High-dimensional entanglement promises to boost the information capacity and resilience to noise of photonic quantum technologies. In this talk, I will focus on the spatial degree of freedom of photons and how it can be utilized for quantum information processing. I will describe our work on the scattering of quantum light in disordered media [1], including scattering compensation [2], Hanbury Brown Twiss (HBT) interference [3], and coherent backscattering [4] of entangled photons. I will then show our recent results on manipulating high-dimensional entanglement using multi-plane light conversion [5] for entanglement certification in large cluster states.

[1] Ohad Lib, and Yaron Bromberg. "Quantum light in complex media and its applications." Nature Physics 18.9 (2022)

[2] Ohad Lib Giora Hasson, and Yaron Bromberg. "Real-time shaping of entangled photons by classical control and feedback." Science Advances 6.37 (2020)

[3] Ohad Lib, and Yaron Bromberg. "Thermal biphotons." APL Photonics 7.3 (2022)

[4] Mamoon Safadi, Ohad Lib, et al. "Coherent backscattering of entangled photon pairs." Nature Physics 19.4 (2023)‏

[5] Ohad Lib, Kfir Sulimany, and Yaron Bromberg. "Processing entangled photons in high dimensions with a programmable light converter." Physical Review Applied 18.1 (2022)

Journal Club

• Non-destructive inelastic recoil spectroscopy of a single molecular ion (Orr Barnea)

A novel single molecule technique is demonstrated that is compatible with high precision measurements and obtained the spectrum of two molecular ion species. While the current result yields modest spectral resolution due to a broad light source, The method is expected to ultimately provide resolution comparable to quantum logic methods with significantly less stringent requirements. Adaptations of this technique will prove useful in a wide range of precision spectroscopy arenas including the search for parity violating effects in chiral molecules. I will present a qualitative comparison between this method and quantum logic spectroscopy and the tradeoff between them.

• Enhancing the lifetime of a superconducting cavity qubit through environment monitoring and feedback (Uri Goldblatt)

Bosonic qubits encoded in superconducting cavities are a promising approach for realizing quantum memories and bosonic codes with built-in protection against decoherence. However, a noisy ancilla qubit is required to encode and manipulate the bosonic qubit. As a result, ancilla errors propagate to the cavity, dephasing the cavity-encoded qubit. This error propagation presented a major limitation in previous experiments with bosonic qubits. I'll present a thorough review of this phenomenon as well as a novel error mitigation protocol based on repeated measurements and real-time feedback to suppress this error propagation. I'll demonstrate the effect of this procedure on the coherence time of the bosonic qubit.

Logical qubit quantum computing with neutral atom arrays

Useful quantum computing will likely require large quantum computers with very low error rates, potentially achievable with quantum error correction (QEC). In QEC, errors are suppressed by nonlocally encoding information on logical qubits. I’ll review our recent report on a programmable logical-qubit quantum processor based on reconfigurable neutral atom arrays [1]. We realize up to 48 logical qubits and hundreds of entangling gates, using up to 280 physical qubits, high gate fidelities [2], arbitrary connectivity, and parallel and arbitrary single-site control. We demonstrate fault-tolerant logical qubit preparation, a logical GHZ state preparation circuit and full state tomography, improvement of a two-qubit logic gate by scaling surface code distance (up to d=7), mid-circuit feed forward, and computationally complex circuits including many non-Clifford gates. We explore the latter via sampling and measurements of entanglement entropy. I’ll discuss our vision for large scale error-corrected quantum processors based on the key concepts of hardware-efficient transversal gates and a multi-zoned architecture, as well as the main challenges for further scaling. Time permitting, I’ll briefly touch on recent results in analog quantum simulation with atom arrays, including explorations of quantum coarsening and novel Hamiltonian engineering techniques. 

[1] Bluvstein et al. Nature (2023) 

[2] Evered et al. Nature (2023) 

Highly nonlinear ultrafast dynamics in liquids and quantum matter

High harmonic generation (HHG) is a nonlinear frequency up-conversion process that occurs when intense laser pulses irradiate matter. In gas-phase it has been extensively studied and is very well-understood (e.g. leading to the 2023 Physics Nobel Prize for attosecond science). In solids, research is ongoing, but a consensus is forming for the dominant HHG mechanisms. In liquids however, no established theoretical model for HHG exists, and the underlying chemical and physical mechanisms remain unidentified. Advancement on this front may lead to novel light sources, and are especially appealing for ultrafast spectroscopy of chemistry in solutions. I will present our recent efforts in tackling this problem with a combination of ab-initio calculations[1], semi-analytical models, and experimental data obtained by collaborators at ETHZ. I will show that HHG in liquids is strongly affected by the electronic mean-free-path, thus allowing its extraction from all-optical measurements, and demonstrating the first application of high harmonic spectroscopy in liquids[2]. I will also show that higher-order scattering processes play a central role in the higher-energy part of liquid-HHG. Lastly, I’ll discuss my recent works on high harmonic spectroscopy of topological phases of matter (challenging the current conception in the field that topology strongly affects solid HHG)[3], and on strong-field driving of attosecond magnetization dynamics in quantum materials, constituting the prediction for the fastest light-driven magnetization dynamics to date[4].

[1] Neufeld et al., JCTC 18, 4117 (2022). https://doi.org/10.1021/acs.jctc.2c00235.

[2] Mondal*, Neufeld* et al., Nat. Phys. (2023). https://doi.org/10.1038/s41567-023-02214-0. 

[3] Neufeld et al., PRX 13, 031011 (2023). https://doi.org/10.1103/PhysRevX.13.031011.

[4] Neufeld et al., npj Comp. Mat. 9, 39 (2023). https://doi.org/10.1038/s41524-023-00997-7.

Temperature dependent spectroscopy of colloidal nano-crystals and coherent image scanning CARS imaging

In this talk I will present our modest contribution in two branches of optical microscopy: a novel application of a spectroscopic technique in the study of semiconductor nano-crystals, and the development of a new non-linear microscopy scheme: phase-resolved, super-resolved CARS imaging.

Excitons in colloidal semiconductor nanoplatelets (NPLs) are weakly confined in the lateral dimensions. This results in significantly smaller Auger rates and, consequently, larger biexciton quantum yields, when compared to spherical quantum dots (QDs). Utilizing the cascaded nature of bi-excitonic emission to perform a time gated photon correlation experiment, we studied the temperature dependence of Auger and radiative rates in NPLs. We showed how using this method the Auger rate can be directly measured for single particles. We found that the Auger rate is largely temperature independent. This result support the claim that colloidal NPLs behave like two-dimensional quantum wells.

Technical advances made in the last two decades have pushed the boundary of the vibrational spectroscopic imaging field, and in particular Coherent Anti-stokes Raman Scattering (CARS) imaging, to a powerful tool for biological, medical and non-destructive applications. Separately, Image Scanning Microscopy (ISM) uses simple manipulation, namely pixel reassignment, to enhance the resolution of a confocal microscope without loss of signal. However, its application is predicated upon the signal being incoherent, as is the case for fluorescence. In order to adept this method to CARS imaging, we have designed and constructed a phase-resolved CARS microscope. Resolving the full field, we demonstrate super-resolved CARS imaging.

Benjamin, E., Yallapragada, V.J., Tenne, R., Amgar, D., Yang, G., Oron, D., 2020. Temperature

dependence of excitonic and biexcitonic decay rates in colloidal nanoplatelets

by time gated photon correlation. The Journal of Physical Chemistry Letters, 11 (16), pp.6513-6518.

Quantum imaging with free electrons and light

The ability to control and manipulate free electrons and light is interesting for its fundamental aspects, while its development for imaging applications has seen great progress, enabling imaging at increasing sensitivity and resolution. Recent developments in quantum information and quantum metrology have inspired a growing interest in developing techniques that manipulate free electrons and light for applications of quantum information processing, as well as to attain quantum limits in imaging applications. In the first part of the talk, I will focus on free electrons, where I will describe a technique to manipulate the transverse wavefunction of free electrons using thin photodiodes illuminated with patterned continuous wave light. These manipulations could in the future allow free-electron entanglement and quantum simulations using free electrons, as well as advanced applications of electron microscopy. [1] In the second part of the talk, I will present a classical technique to enhance the sensitivity and throughput of imaging a dynamic sample that approaches the quantum limit, surpassing sensitivity enhancement of all previous demonstrations of imaging that use squeezed light or entanglement. [2]

References:

[1] S. Koppell, Y. Israel, A. Bowman, B. Klopfer, M. Kasevich, Appl. Phys. Lett. 120, 190502 (2022)

[2] Y. Israel, L. Reynolds, B. Klopfer, M. Kasevich, Optica, 10, 491-496 (2023)

From Multimode Nonlinear Optics to High-Dimensional Quantum Communications

Quantum photonics often relies on nonlinear optics for the generation of photons, followed by reconfigurable linear optical networks for coherent control. In this talk, I will review our study of multimode nonlinear optics in fibers [1,2], which also enabled our realization of an all-fiber entangled photon pairs source [3]. These photons are spatially entangled in the eigenmodes of the multimode fiber, allowing for high-dimensional quantum communications. I will then present a couple of methods to coherently control such states. The first is achieved by multiplane light conversion based on a spatial light modulator [4], while the second is by employing a “Fiber piano” [5]; a piezo-actuator array that deforms the multimode fiber. Finally, I will introduce a novel Quantum Key Distribution protocol that utilizes high-dimensional encoding to boost the secure key rate and its experimental implementation [6].

[1] Kfir Sulimany, et al. Physical Review Letters 121.13 (2018): 133902.

[2] Kfir Sulimany, et al. Optica 9.11 (2022): 1260-1267.

[3] Kfir Sulimany, and Yaron Bromberg. npj Quantum Information 8.1 (2022): 1-5.

[4] Ohad Lib, Kfir Sulimany, and Yaron Bromberg. Physical Review Applied 18.1 (2022): 014063.

[5] Finkelstein, Zohar, Kfir Sulimany, et al. APL Photonics 8, no. 3 (2023).

[6] Kfir Sulimany, et al. arXiv preprint arXiv:2105.04733 (2021). Under review.

Generating complex entanglement in trapped-ions based quantum computers

Large, coherent, and well-controlled quantum computers are expected to have a tremendous effect on various computational fields such as material science, chemistry, medicine, infrastructure etc. Thus, a wide-ranging effort is taking place, involving many academic, industry and government participants, with the goal of constructing a useful quantum computer.

Our modest contribution to this global effort will be presented in the context of quantum computers that are based on electrically trapped linear crystals of atomic ions. Such quantum computers offer a unique property, namely a substantial and non-local coupling between all their constituent qubits, that stems from the long-range repulsive Coulomb interaction between the ions in the crystal.

This interaction can be controlled and shaped by driving the trapped ions with a fine-tuned multi-tone drive. We demonstrate, theoretically and experimentally, that such a control enables performing programmable, large scale and simultaneous logical operation on the trapped ions, as well as making these operations resilient to various sources of error and noise. Furthermore, we use spectral control to perform simulations of
quantum systems, that manifest geometries that do not necessarily conform to the linear geometry of the ion-crystal, and exhibit interactions between its constituent particles.
 

Zoom link:

https://weizmann.zoom.us/j/93287950378?pwd=WmVncU53eXRXR0Y3cWg3eklPQlBqZz09

Local dissipation effects in the driven-dissipative Dicke phase transition

The driven Dicke model, where an ensemble of atoms is driven by an external field and undergoes collective spontaneous emission through a leaky cavity mode, is a paradigmatic model that exhibits a driven-dissipative phase transition as a function of driving power. Recently, a highly analogous phase transition was experimentally observed, not in a cavity setting, but rather in a freespace atomic ensemble. Motivated by this, we present our ongoing efforts to better characterize the free-space problem, and understand possible differences compared to the cavity version. We specifically discuss a minimal model for the free space based on the Maxwell-Bloch equations. We find that the presence of local dissipation dramatically changes the properties of the phase transition. In particular, we present preliminary arguments that suggest that the free-space case might exhibit a smooth crossover rather than a true phase transition in the thermodynamic (large atom number) limit.

Communication with quantum circuits

The field of quantum communication involves sending quantum states from one location to another. This has potential applications in building secure communication channels through quantum cryptography as well as in sharing resources between quantum computers that are part of a quantum network. Quantum communication protocols based on multi-photon states can support greater transmitted information density than those relying on single photon states. Bidirectional communication would further increase channel efficiency, but this has not yet been achieved for multi-photon wavepackets at microwave frequencies. In this talk, I will present an experiment demonstrating bidirectional multi-photon transfers between two distant tunable resonators in a superconducting system, enabling single-pass on-demand transfers of photon superposition states.

Metamaterials of fluids of light and sound

Lattices of exciton polariton condensates represent a rich platform for the study and implementation of non-Hermitian non-linear bosonic quantum systems. Actuation with a time dependent drive provides the means, for example, to perform Floquet engineering, Landau-Zenner-Stückelberg state preparation, and to induce resonant inter-level transitions. With this perspective we introduce polaromechanical metamaterials, two-dimensional arrays of mm-size zero-dimensional traps confining light-matter polariton fluids and GHz phonons.

A strong exciton-mediated polariton-phonon interaction [1] can be exploited in these metamaterials, both using electrically injected bulk-acoustic waves [2] or self-induced coherent mechanical oscillations [3], to induce a time-dependence in the level energies and/or in the inter-site polariton coupling J(t). This has remarkable consequences for the dynamics. For example, when locally perturbed by continuous wave optical excitation, polariton condensates respond by locking the energy detuning between neighbor sites at multiples of the phonon energy [4]. We theoretically describe these observations in terms of synchronization phenomena involving the polariton and phonon fields. We study lattices of closely connected traps (defined by a linear optomechanical coupling), and also well separated t! raps (characterized by a quadratic optomechanical coupling), and discuss the role of dissipation and non-linearities in the stability of the observed asynchronous locking. The described metamaterials open the path for the study of non-reciprocal transport in dissipative quantum light fluids spatially and temporally modulated by GHz hypersound.

1. P. Sesin et al., Giant optomechanical coupling and dephasing protection with cavity exciton-polaritons, arXiv:2212.08269.
2. A. S. Kuznetsov et al., Electrically Driven Microcavity Exciton-Polariton Optomechanics at 20 GHz, Physical Review X 11, 021020 (2021).
3. D. L. Chafatinos et al., Polariton-Driven Phonon Laser, Nature Communications 11, 4552 (2020).
4. R D. L. Chafatinos et al., Asynchronous Locking in Metamaterials of Fluids of Light and Sound, arXiv:2112.00458, Nature Communications (in press).

Optical Multidimensional Coherent Spectroscopy

The concept of multidimensional coherent spectroscopy originated in NMR where it enabled the determination of molecular structure. The key concept is to correlate what happens during multiple time periods between pulses by taking a multidimensional Fourier transform. The presence of a correlation, which is manifest as an off-diagonal peak in the resulting multidimensional spectrum, indicates that the corresponding resonances are coupled. Migrating multidimensional Fourier transform spectroscopy to the optical regime is difficult because phases are critical. I will give an introduction to optical two-dimensional coherent spectroscopy, using an atomic vapor as a simple test system. I will then present our use of it to study optical resonances due to excitons in semiconductor nanostructures including transition metal dichalcogenides, where it is useful to incorporate laser-scanning microscopy.

Quantum computing with trapped ions

Quantum technologies allow for fully novel schemes of hybrid computing. We employ modern segmented ion traps. I will sketch architectures, the required trap technologies and fabrication methods, control electronics for quantum register reconfigurations, and recent improvements of qubit coherence and gate performance. Currently gate fidelities of 99.995% (single bit) and 99.8% (two bit) are reached. We are implementing a reconfigurable qubit register and have realized multi-qubit entanglement [1] and fault-tolerant syndrome readout [2] in view for topological quantum error correction [3] and realize user access to quantum computing [4]. The setup allows for mid-circuit measurements and real-time control of the algorithm. We are currently investigating various used cases, including variational quantum eigensolver approaches for chemistry or high energy relevant models, and measurement-based quantum computing. The fully equipped in house clean room facilities for selective laser etching of glass enables us to design and fabricate complex ion trap devices, in order to scale up the number of fully connected qubits. Also, we aim for improving on the speed of entanglement generation. The unique and exotic properties of ions in Rydberg states [5] are explored experimentally, staring with spectroscopy [6] of nS and nD states where states with principal quantum number n=65 are observed. The high polarizability [7] of such Rydberg ions should enable sub-µs gate times [8].

1. Kaufmann er al, Phys. Rev. Lett. 119, 150503 (2017)
2. Hilder, et al., Phys. Rev. X.12.011032 (2022)
3. Bermudez, et al, Phys. Rev. X 7, 041061 (2017)
4. https://iquan.physik.uni-mainz.de/
5. A. Mokhberi, M. Hennrich, F. Schmidt-Kaler, Trapped Rydberg ions: a new platform for quantum information processing, Advances In Atomic, Molecular, and Optical Physics, Academic Press, Ch. 4, 69 (2020), arXiv:2003.08891
6. Andrijauskas et al, Phys. Rev. Lett. 127, 203001 (2021)
7. Niederlander et al, NJP 25 033020 (2023)
8. Vogel et al,  Phys. Rev. Lett. 123, 153603 (2019)

Journal club

Collective shift in resonant light scattering by a one-dimensional atomic chain

We experimentally study resonant light scattering by a one-dimensional randomly filled chain of cold two-level atoms. By a local measurement of the light scattered along the chain, we observe constructive interferences in light-induced dipole-dipole interactions between the atoms. They lead to a shift of the collective resonance despite the average interatomic distance being larger than the wavelength of the light. This result demonstrates that strong collective effects can be enhanced by structuring the geometrical arrangement of the ensemble. We also explore the high intensity regime where atoms cannot be described classically. We compare our measurement to a mean-field, nonlinear coupled-dipole model accounting for the saturation of the response of a single atom.

Phys. Rev. Lett. 124, 253602 (2020)

Tomography of Feshbach Resonance States

Quantum phenomena that lead to the formation of long-lived collision complexes, such as scattering resonances, play a central role in the outcome of cold atomic and molecular collisions. These phenomena are fundamental probes of the fine details of internuclear interactions, and their understanding is crucial for future quantum technologies with cold molecules. In this talk, I will show a new method to populate and probe near-threshold Feshbach resonance states. In addition to the resonance energy, we obtain the state-to-state distribution of final scattering states, providing a tomographic picture of the resonance state [1]. Our method is based on the coincidence detection of electron/ion momenta in Penning ionization collisions between metastable noble gas atoms and neutral molecules/atoms [2]. We demonstrate our ability to filter out the resonance pathway from complex collision processes involving reactive, inelastic, and elastic pathways. We obtain several tens of quantum numbers per measurement without any laser detection schemes. We present an excellent match between theory and experiment, which allowed us to demonstrate a unique quantum signature of the resonance states on the final state distribution. In addition, we present an experimental scheme for control of the final state distribution, which is based on the initial constraint of total angular momentum at the Ionization step of the dynamics. The latter is motivated by our recent observation of a partial wave resonance at the lowest state of relative angular momentum [3].

1. Margulis B. et al, arXiv:2212.02828 (2022).
2. Margulis B. et al, Nature Communications, 11(1), 1-6 (2020). [3] Margulis B. et al, Physical Review Research, 4(4), 043042 (2022).

Quantum Information Processing with Light: from Single Photons to Continuous Variables

In this talk, I will present my journey moving from working with single photons to continuous variables. The signal-to-noise ratio (SNR) of range measurements can be improved by quantum detection and quantum light sources (quantum ranging). In the first part, I will present the theory of quantum ranging in the framework of Gaussian states. I will show that an optimal detection strategy, which minimizes the detection errors, can be applied for an arbitrary return state from the target. Then I will discuss the use of quantum light in the same scenario. Optimal detection is important in high-loss mediums, such as underwater, where low signal returns and maximizing its information is needed. In the second part, I will present experimental results of improved sensitivity of a temperature sensor and quantum simulations with single photons and will present my plans to extend the theory and experiments to Gaussian states. I will show simulations of a basic transition of quantum gravity theory and discuss scaling it up to complex transitions. Complex versions of these simulations have the potential to advance the research of basic science.

White-light holographic imaging using the optical coherence matrix formalism (or how to beat classical light-field imaging’s resolution limit)

Light-field cameras promised to revolutionize imaging by capturing and recording the propagation paths of light-rays through space. This light-field information, equivalent to canonical optical phase space, supposedly holds the “sys-admin” password to optical imaging. Digital post-processing and manipulation can allow digital refocusing of rays, correction of optical aberrations, as well as calculating the distance to every point in the imaged scene. However, once this technology was put into practice, its severe limitations and trade-offs became apparent. The main problem is that conventional light-field imaging contains an inherent trade-off between the light-rays’ angular information and the overall image resolution, analogous to Heisenberg’s uncertainty principle. PxE Holographic Imaging has developed a white-light holographic imaging camera that overcomes these limitations allowing highly accurate depth inference, digital refocusing and deblurring, as well as holographic, wavefront, and spectral imaging to be performed with no compromise on image resolution. In this talk we’ll explain the physics behind this breakthrough, and it’s relation to the optical coherence matrix formalism, the Wigner distribution, von Neumann measurements, and positive-operator-valued measures (POVMs).

Non-Thermal Pathways to the Origin of a Charge Density Wave

Highly correlated systems host in many cases a complex electronic phase diagram, with different phases competing or emerging from one-another. A new group of kagome metals AV3Sb5 (A = K, Rb, Cs) exhibit a variety of intertwined unconventional electronic phases, which emerge from a puzzling charge density wave phase. Understanding of this parent charge order phase is crucial for deciphering the entire phase diagram. However, the mechanism of the charge density wave is still controversial, and its primary source of fluctuations – the collective modes – have not been experimentally observed. In my talk I will show how we use ultrashort l! aser pulses to melt the charge order in CsV3Sb5 and record the resulting dynamics using femtosecond angle-resolved photoemission. We resolve the melting time of the charge order and directly observe its amplitude mode, imposing a fundamental limit for the fastest possible lattice rearrangement time. These observations together with ab-initio calculations provide clear evidence for a structural rather than electronic mechanism of the charge density wave, providing a path towards better understanding of the unconventional phases hosted on the kagome lattice.

Heralded Spectroscopy - A new probe for nanocrystal multiexciton photophysics

Emitters of quantum light are at the core of quantum optic science and a key resource for emerging classical and quantum technologies. Yet, to date, the tools available to study multiple-photon quantum light sources, specifically temporally and spectrally in parallel, have been limited. A prominent example is multiply-excited semiconductor quantum dots - an intriguing system that features rich physics and technological potential but lacks direct observation techniques.

In this talk, I will introduce a new type of spectroscopy,Heralded Spectroscopy, specifically tailored to tackle this challenge. The technique harnesses photon correlations, a resource that has played a seminal role in quantum optics (as exemplified in this year’s Nobel Prize in physics) and is now showing renewed potential with the maturation of novel detector technologies. I will describe the Heralded Spectroscopy method and some of the insights it uncovered into quantum dot physics, as well as current adaptations and their potential to further extend the boundaries of spectroscopy and our understanding of quantum light emitters.

1. GL et al., ACS Photonics, 9 (9), pp. 2891–2904 (2022)
2. GL et al., ACS Nano, 15 (12), pp. 19581-19587 (2021)
3. GL et al., Nano Letters, 21 (16), pp. 6756–6763 (2021)
4. GL et al., Optics Express, 27 (23), pp.32863-32882 (2019)

Quantum Algorithms as the Level-band problem

Many quantum algorithms can be seen as a transition from a well-defined initial quantum state of a complex quantum system, to an unknown target quantum state, corresponding to a certain eigenvalue either of the Hamiltonian or of a transition operator. Often such a target state corresponds to the minimum energy of a band of states. In this context, approximate quantum calculations imply transitions not to a single, minimum energy, state but to a group of states close to the minimum. We consider the dynamics and the results of two possible realizations of such a process - transition of population from a single, initially populated isolated level to quantum states at the edge of a band of levels. The first case deals with time-independent Hamiltonians, while the other with a moving isolated level. We demonstrate that the energy width of the population distribution over the band is mainly dictated by the time-energy uncertainty principle, although the specific shape of the distribution depends on the particular setting. We consider the role of the statistics of the coupling matrix elements between the isolated level and the band levels. We have chosen the multiphoton Raman absorption by an ensemble of Rydberg atoms as the model for our analysis, although the results obtained can equally be applied to other quantum computing platforms.

Journal Club

High-efficiency photoemission from magnetically doped quantum dots driven by multi-step spin-exchange Auger ionization (Nadav Frenkel)

The ability to use visible light for electron photoemission and manipulation of 'hot' charge carriers is of great interest for applications in photochemistry and energy harvesting. In semiconductors, the realization of such schemes is complicated by extremely fast intraband cooling. Auger recombination is a process wherein an exciton recombines non-radiatively, exciting another charge carrier to a higher energy state. In semiconductor nanocrystals, e.g., quantum dots, Auger interactions are enhanced, providing a better chance for manipulating 'hot' carriers before they undergo energy dissipation. Here, we demonstrate that doping CdSe quantum dots with manganese atoms introduces fast spin-exchange interactions, accelerating Auger rates even more. Moreover, we present how the doping 'unlocks' a two consecutive steps Auger process that enables highly efficient electron photoemission under excitation with visible-light pulses.

[1] Livache, C., Kim, W.D., Jin, H.et al.High-efficiency photoemission from magnetically doped quantum dots driven by multi-step spin-exchange Auger ionization.Nat. Photon. 16,433–440 (2022).

Broadband optical phase modulation by colloidal CdSe quantum wells (Daniel Amgar)

Two-dimensional (2D) semiconductors are primed to realize a variety of photonic devices that rely on the transient properties of photogenerated charges, yet little is known on the change of the refractive index. The associated optical phase changes can be beneficial or undesired depending on the application, but require proper quantification. Measuring optical phase modulation of dilute 2D materials is, however, not trivial with common methods.

The work I will present demonstrates phase modulation of light across a broad spectrum by 2D CdSe nanoplatelets using a femtosecond interferometry method. Moreover, they developed a toolbox to calculate the time-dependent refractive index of colloidal 2D materials from widely available transient absorption experiments using a modified effective medium algorithm. The results show that the excitonic features of 2D materials yield a broadband, ultrafast, and sizable phase modulation.

I. Tanghe et al.,Broadband Optical Phase Modulation by Colloidal CdSe Quantum Wells,Nano Lett.,2022, 22, 1, 58–64.

Journal Club

X-Ray Free Electron Lasers from Laser-Plasma Accelerators (Aaron Liberman)

X-Ray free electron lasers (XFELs), able to produce intense, short duration radiation with wavelengths smaller than an angstrom, are a critical tool in physics, chemistry, and biology. They can unlock the ability to image 3D protein structures that have evaded traditional x-ray crystallography. Conventional XFELs, such as the European XFEL, rely on radio-frequency accelerators which are limited in the magnitude of the electric fields they can sustain. Thus, these facilities are kilometer scale, multibillion dollar complexes. Laser-plasma accelerators (LPAs), which can achieve field gradients of over three orders of magnitude greater than RF accelerators, provide a promising path towards the miniaturization of these essential machines. For years, however, the strict requirements on the electron beam quality that XFELs impose prevented the achievement of exponential-gain from LPA generated electron beams. In this talk, I will present the first experimental realization of an exponential-gain, LPA based XFEL. This proof-of-concept experiment promises to path the way to lab-scale XFELs.  

[1] W. Wang et al, “Free-electron lasing at 27 nanometres based on a laser wakefield accelerator,” Nature 595, 516-520 (2021)  

Single-Photon Storage in a Ground-State Vapor Cell Quantum Memory (Ohad Yogev)

Interfaced single-photon sources and quantum memories for photons together form a foundational component of quantum technology. Achieving compatibility between heterogeneous, state-of-the-art devices is a long-standing challenge. We built and successfully interfaced a heralded single-photon source based on cavity-enhanced spontaneous parametric down-conversion in ppKTP and a matched memory based on electromagnetically induced transparency in warm 87Rb vapor. The bandwidth of the photons emitted by the source is 370MHz, placing its speed in the technologically relevant regime while remaining well within the acceptance bandwidth of the memory. Simultaneously, the experimental complexity is kept low, with all components operating at or above room temperature. Read-out noise of the memory is considerably reduced by exploiting polarization selection rules in the hyperfine structure of spin-polarized atoms. For the first time, we demonstrate single-photon storage and retrieval in a ground-state vapor cell memory, with g(2) c; ret = 0:177(23) demonstrating the single-photon character of the retrieved light. Our platform of single-photon source and atomic memory is attractive for future experiments on room-temperature quantum networks operating at high bandwidth.

Buser, Gianni, et al. "Single-Photon Storage in a Ground-State Vapor Cell Quantum Memory." arXiv preprint arXiv:2204.12389 (2022).

Journal Club

Efficient generation of entangled multi-photon graph states from a single atom

Photonic quantum computation has great promise to pave the way for fault-tolerant quantum computers, due to the possibility to scale-up the number of qubits with large entangled states[1]. Yet, photonic quantum computation suits a different computational scheme – Measurement based quantum computation. This scheme demands generation of large entangled/cluster states of photons. The major effort for generating these states is concentrated in probabilistic method using spontenouos parametric down conversion (spdc) and linear optics, e.g. beam splitters and single photon detectors. It can be overcome by utilizing single atom interacting with cavity that can offer a deterministic scheme for generation of large entangled states. In this context, I will elaborate on the results of the following paper[2], which demonstrated generation of up to 14-qubit GHZ states along with up to 12-qubit cluster state.

1. Bombin, H., Kim, I. H., Litinski, D., Nickerson, N., Pant, M., Pastawski, F., ... & Rudolph, T. (2021). Interleaving: Modular architectures for fault-tolerant photonic quantum computing. arXiv preprint arXiv:2103.08612.‏
2. Thomas, P., Ruscio, L., Morin, O., & Rempe, G. (2022). Efficient generation of entangled multi-photon graph states from a single atom. arXiv preprint arXiv:2205.12736. https://arxiv.org/abs/2205.12736

journal club

Probing Infinite Many-Body Quantum Systems with Finite-Size Quantum Siumulators (Lee Peleg)

Experimental studies of synthetic quantum matter are necessarily restricted to approximate ground states prepared on finite-size quantum simulators. In general, this limits their reliability for strongly correlated systems, for instance, in the vicinity of a quantum phase transition (QPT). Here, we propose a protocol that makes optimal use of a given finite-size simulator by directly preparing, on its bulk region, a mixed state representing the reduced density operator of the translation-invariant infinite-sized system of interest. This protocol is based on coherent evolution with a local deformation of the system Hamiltonian. For systems of free fermions in one and two spatial dimensions, we illustrate and explain the underlying physics, which consists of quasiparticle transport towards the system’s boundaries while retaining the bulk “vacuum.” For the example of a nonintegrable extended Su-Schrieffer-Heeger model, we demonstrate that our protocol enables a more accurate study of QPTs. In addition, we demonstrate the protocol for an interacting spinful Fermi-Hubbard model with doping for one-dimensional chains and a small two-leg ladder, where the initial state is a random superposition of energetically low-lying states.

Third harmonic Mie scattering from semiconductor nanohelices (Lotem Alus)

Chiroptical spectroscopies provide structural analyses of molecules and nanoparticles but they require sample volumes that are incompatible with generating large chemical libraries. New optical tools are needed to characterize chirality for the ultrasmall (<1 µl) volumes required in the high-throughput synthetic and analytical stations for chiral compounds. Here we show experimentally a novel photonic effect that enables such capabilities—third-harmonic Mie scattering optical activity—observed from suspensions of CdTe nanostructured helices in volumes <<1 µl. Third-harmonic Mie scattering was recorded on illuminating CdTe helices with 1,065, 1,095 and 1,125 nm laser beams and the intensity was around ten-times higher in the forward direction than sideways. The third-harmonic ellipticity was as high as 3° and we attribute this effect to the interference of chiral and achiral effective nonlinear susceptibility tensor components. Third-harmonic Mie scattering on semiconductor helices opens a path for rapid high-throughput chiroptical characterization of sample volumes as small as 10−5 µl.

Journal club

Attosecond-Level Relativistic Electron Beams from Laser-Plasma Accelerators (Eitan Y. Levine)

Laser-plasma acceleration (LPA) is a mechanism by which a short, ultra-intense laser pulse is focused onto a target, ionizing it and driving a plasma wave in its wake. This wake-field can be used to trap and accelerate electron bunches to relativistic speeds, and also to generate via these electrons a very short x-ray pulse, known as betatron radiation, sharing the duration of its generating electron bunch. Since ultra-short x-ray pulses can be used to probe ultra-short phenomena, measurement and reduction of the accelerated bunch duration are among the goals of the LPA field. In this talk, I will briefly introduce the basic physics of LPA, present the coherent transition radiation (CTR) method for bunch duration and profile measurement, and show predictions for pushing the frontier of ultra-short electron bunch generation.

1. Lundh, O., Lim, J., Rechatin, C. et al. Few femtosecond, few kiloampere electron bunch produced by a laser–plasma accelerator. Nature Phys 7,219–222 (2011). https://doi.org/10.1038/nphys1872
2. Ferri, J. et al.Generation of attosecond electron bunches and x-ray pulses from few-cycle femtosecond laser pulses. Plasma Phys. Control. Fusion 63 045019 (2021).  

Programmable interactions and emergent geometry in an array of atom clouds (Yotam Shapira)

Interacting quantum many-body systems exhibit a wide range of interesting phenomena, such as exotic phases of matter and rich entanglement structures. However these systems are typically analytically intractable and challenging to probe experimentally. This is alleviated by experimentally studying analogous yet controllable systems known as quantum simulators. Here I will follow the realization of Periwal et al [1] and present their realization of a quantum simulator made of an array of atomic ensembles within an optical cavity. The combination of the cavity and a magnetic field gradient along the array axis enables simulation of a wide range of emergent geometries such as a ring, a triangular ladder, a Mobius strip as well as non-Archimedean geometries. The methods and results demonstrated in [1] open up new opportunities for studies of many exciting fields such as quantum gravity, frustrated magnetization, spin glass-models etc.

1. Avikar Periwal, Eric S. Cooper, Philipp Kunkel, Julian F. Wienand, Emily J. Davis & Monika Schleier-Smith, Programmable interactions and emergent geometry in an array of atom clouds, Nature 600, 630-635 (2021).

Journal club

3D printable diffractive optical elements by liquid immersion (Lior Beck)

shape a wavefront, different optical devices can be used, these include diffractive optical elements (DOE), spatial light modulators (SLM) and deformable mirrors. In this work a rather simple and cost-effective method to scale up feature size of DOE has been demonstrated, changing the relevant feature size from tens of nanometers to tens of micrometers. This is done by immersing the DOE in a near index matched solution. The phase accumulated by the DOE can be tuned, this tunability is demonstrated by modifying the point-spread-function (PSF) in a 3D localization microscope, where the position of single molecules in cells were tracked with high precision.

Reut Orange-Kedem, Elias Nehme, Lucien E. Weiss, Boris Ferdman, Onit Alalouf, Nadav Opatovski and Yoav Shechtman  

A look under the tunnelling barrier via attosecond-gated interferometry (Omer Kneller)

Interferometry has been at the heart of wave optics since its early stages, resolving the coherence of the light field and enabling the complete reconstruction of the optical information it encodes. Transferring this concept to the attosecond time domain shed new light on fundamental ultrafast electron phenomena. In my talk I will describe our recent work [1], introducing attosecond-gated interferometry. This scheme probes one of the most fundamental quantum mechanical phenomena, field-induced tunnelling. Our experiment probes the evolution of an electronic wavefunction under the tunnelling barrier and records the phase acquired by an electron as it propagates in a classically forbidden region. We identify the quantum nature of the electronic wavepacket and capture its evolution within the optical cycle. Attosecond-gated interferometry has the potential to reveal the underlying quantum dynamics of strong-field-driven atomic, molecular and solid-state systems.

[1] Kneller, O., Azoury, D., Federman, Y. et al. A look under the tunnelling barrier via attosecond-gated interferometry. Nat. Photon. 16, 304–310 (2022).

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

journal club

Measuring exciton diffusion rate, Auger and singlet-singlet annihilation rates, and the true number of chromophores using picosecond time-resolved photon antibunching (Dekel Nakar)

The photon statistics of fluorescence from single quantum systems (single chromophores) shows photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here the authors develop picosecond time-resolved antibunching to identify and analyze such processes. This method is first used on well-defined multichromophoric DNA-origami structures to precisely determine the distance-dependent rates of annihilation between excitons. Then, this allows to measure exciton diffusion in mesoscopic conjugated-polymer aggregates with different spatial ordering (H- vs. J-type conjugation). The authors distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Overall, using this method, excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

Hedley, G.J., …, Jan Vogelsang et al. Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores. Nat Commun 12,1327 (2021). https://doi.org/10.1038/s41467-021-21474-z  

Pauli blocking of atom-light scattering (Eran Reches)

Fermi’s golden rule reveals that the transition rate between two coupled states depends on the density of final states. It is well-known, for instance, that a resonant cavity can enhance the spontaneous emission rate of an atom by increasing the density of states of light. Similarly, reducing the density of final momentum modes of the atomic motion is expected to suppress the rate of radiative processes. This can happen for fermionic atoms embedded in a Fermi sea via the Pauli exclusion principle, which forbids final momentum modes already occupied by other atoms.

In my talk I will present the work in Ref. [1], where the authors experimentally demonstrate the suppression of light scattering rates in a quantum degenerate Fermi gas of strontium atoms by up to a factor of 2, compared with a thermal gas. I will also compare key aspects of their experiment to the work of other groups [2,3].

[1] Sanner, C., Sonderhouse, L., Hutson, R. B., Yan, L., Milner, W. R., & Ye, J. (2021). Pauli blocking of atom-light scattering. Science, 374(6570), 979–983. https://doi.org/10.1126/science.abh3483

[2] Deb, A. B., & Kjærgaard, N. (2021). Observation of Pauli blocking in light scattering from quantum degenerate fermions. Science, 374(6570), 972–975. https://doi.org/10.1126/science.abh3470

[3] Margalit, Y., Lu, Y.-K., Top, F. Ç., & Ketterle, W. (2021). Pauli blocking of light scattering in degenerate fermions. Science, 374(6570), 976–979. https://doi.org/10.1126/science.abi6153

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09
 

Journal club

Realization of a 9-qubit Bacon-Shor Code (David Schwerdt)

Recently there have been several experimental demonstrations of quantum error correction (QEC). These demonstrations are of great interest as they pave the way to running large-scale quantum computing protocols that are resilient against physical qubit errors. For any realization of QEC to be viable it must be fault tolerant (FT), in that prevents the spread of errors.

This talk will mainly focus on a FT realization of the Bacon-Shor code in a trapped ion system [1]. The authors demonstrate FT state preparation, stabilizer measurements, and logical-qubit operations. They show the successful correction of any single-qubit errors in a single round of QEC. This work provides an outlook towards implementing circuits with continuously-stabilized logical qubits.

[1] Egan, L. et al. (2021) “Fault-tolerant control of an error-corrected qubit.” Nature 598, 281-286  

3D printable diffractive optical elements by liquid immersion (Lior Moshe Beck)

To shape a wavefront, different optical devices can be used, these include diffractive optical elements (DOE), spatial light modulators (SLM) and deformable mirrors. In this work a rather simple and cost-effective method to scale up feature size of DOE has been demonstrated, changing the relevant feature size from tens of nanometers to tens of micrometers. This is done by immersing the DOE in a near index matched solution. The phase accumulated by the DOE can be tuned, this tunability is demonstrated by modifying the point-spread-function (PSF) in a 3D localization microscope, where the position of single molecules in cells were tracked with high precision.

Reut Orange-Kedem, Elias Nehme, Lucien E. Weiss, Boris Ferdman, Onit Alalouf, Nadav Opatovski and Yoav Shechtman

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Why is refractive index so small? From quantum optics to quantum chemistry

It is interesting to observe that all known materials have an index of refraction that is of order unity at visible wavelengths. This is quite different than any other material property (such as density, conductivity, specific heat), which can vary by orders of magnitude, and depends on the system being a gas vs. solid, insulating vs. conducting, etc. Strangely, there is no deep underlying theory of why refractive index has this seemingly universal property. This is despite the immense technological importance that an ultrahigh index material would have, as the index describes how much the wavelength of light can be reduced, and thus directly determines the minimum footprint of optical devices.

Separately, it is well-known within quantum optics that a single, isolated atom can have an extraordinarily strong response to near-resonant light, as characterized by a scattering cross section that is much larger than its physical size. Substituting this known result into standard electrodynamics formulas for material refractive index results in a predicted index of 10^5 at the densities of a solid! Here, we will discuss why these textbook formulas break down, and our ongoing efforts to develop a more fundamental theory of refractive index and its limits. Our theory suggests that the low refractive index observed in everyday life is not necessarily fundamental, and a low-loss, ultrahigh-index material of n~30 might be possible. This theory combines ideas from quantum optics, quantum chemistry, and non-perturbative multiple scattering of light, which suggests why an answer to the refractive index problem might have been elusive in the past.  

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Journal club

Pauli blocking of atom-light scattering (Eran Reches)

Fermi’s golden rule reveals that the transition rate between two coupled states depends on the density of final states. It is well-known, for instance, that a resonant cavity can enhance the spontaneous emission rate of an atom by increasing the density of states of light. Similarly, reducing the density of final momentum modes of the atomic motion is expected to suppress the rate of radiative processes. This can happen for fermionic atoms embedded in a Fermi sea via the Pauli exclusion principle, which forbids final momentum modes already occupied by other atoms.

In my talk I will present the work in Ref. [1], where the authors experimentally demonstrate the suppression of light scattering rates in a quantum degenerate Fermi gas of strontium atoms by up to a factor of 2, compared with a thermal gas.

[1] Sanner, C., Sonderhouse, L., Hutson, R. B., Yan, L., Milner, W. R., & Ye, J. (2021). Pauli blocking of atom-light scattering. Science, 374(6570), 979–983. https://doi.org/10.1126/science.abh3483

The image-forming mirror in the eye of the scallop (Arujash Mohanty)

When we talk about eyes, we perceive it as a structure having one or more lenses for focusing incoming light onto a surface (retina). However, light can also be focused using arrays of mirrors (commonly done in telescopes). A biological example of this is the “Pecten scallop”, which can have up to 200 reflecting eyes that focus light onto two retinas. The layered structure of the mirrors is optimized to reflect the wavelengths of light penetrating the eye of the scallop and is tiled with an assembly of square guanine crystals, which reduces optical aberrations. The image is formed by reflection from the mirrors on a double-layered retina used for separately imaging the peripheral and central fields of view. This tiled, off-axis mirror of the scallop eye bears a striking resemblance to the segmented mirrors of reflecting telescopes. I will be talking about the mechanism of such complex imaging system in terms of imaging quality, structural orientation of the mirrors and the control of the size, shape, and packing density of the mirrors (tiles of guanine) that together make up an image-forming mirror at the back of each of the eyes.

The image-forming mirror in the eye of the scallop ( DOI: 10.1126/science.aam9506 )

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Boosting electron beam energy in laser-plasma accelerators

From facilitating advanced non-destructive material testing to saving lives with radiation treatments for cancer, particle accelerators are everywhere, playing a definitive role in science and society. Conventional accelerators are limited by the electric field gradients generated in radio-frequency (RF) cavities. Thus, a considerable acceleration length is required to achieve the high energies needed for many applications. Laser-plasma accelerators (LPAs), a newer generation of accelerators that operate on a different paradigm, can overcome this limitation, sustaining accelerating fields three orders of magnitude larger than those in RF cavities. LPAs, therefore, allow for a drastic decrease in accelerator size, reducing price and increasing availability. Yet, several challenges remain before LPAs can replace traditional accelerators. Most significantly, in order to be of use in many real-world applications, LPAs must demonstrate the ability to produce stable, efficient, and high-quality GeV electron beams at a high repetition rate. In my talk, I will present the development of new methods that tackle LPA's limitations and aim to increase efficiency and accelerate more energetic electrons.

ZOOM: https://weizmann.zoom.us/j/99391169077?pwd=cktsZENWT3o1OGlYejRoT2FDQSs0UT09

Journal club

Superresolution Microscopy of Optical Fields (Jonathan Wengrowicz)

A scanning probe microscope has been realized using single trapped 87Rb atoms to measure optical fields with subwavelength spatial resolution. The microscope operates by detecting fluorescence from a single atom driven by near-resonant light and determining the ac Stark shift of an atomic transition from other local optical fields via the change in the fluorescence rate. The microscope benchmarked by measuring two standing-wave Gaussian modes of a Fabry-P´erot resonator with optical wavelengths of 1560 and 781 nm. A spatial resolution of 300 nm attained, which is superresolving compared to the limit set by the 780 nm wavelength of the detected light. Sensitivity to short length scale features is enhanced by adapting the sensor to characterize an optical field via the force it exerts on the atom.

(Emma Deist, Justin A. Gerber, Yue-Hui Lu, Johannes Zeiher and Dan M. Stamper-Kurn)  

Photon control and coherent interactions via lattice dark states in atomic arrays (Roni Ben Maimon)

Ordered atomic arrays with subwavelength spacing have emerged as an efficient and versatile light matter interface, where collective interactions give rise to det of super- and subradiant lattice states. Using a spatial modulation of the atomic detuning, it is possible to address and manipulate the highly subradiant states, also known as lattice dark states. More specifically, the lattice dark states can be utilized to store and retrieve single photon with near-unit efficiency, as well as control the temporal, frequency, and spatial degrees of freedom of the emitted electromagnetic field. These results pave the way towards quantum optics and information processing using atomic arrays.

(Oriol Rubies-Bigorda, Valentin Walther, Taylor L. Patti and Susanne F. Yelin)

ZOOM: https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Two-body problem in waveguide quantum electrodynamics

Will consider an interaction of two photons with a periodic array of two-level atoms, coupled to a waveguide. Single-particle eigenstates of this setup are polaritons, hybridized light-atom excitations, that have an intrinsically nonparabolic dispersion law formed by the avoided crossing of light with the atomic resonance. Polaritons repel each other strongly due to the photon blockade. Due to the nonparabolic dispersion, the two-polariton problem becomes significantly different from that of usual massive interacting bosons. In another words, the two-body Dicke model shows new interactions, impossible in e.g. the Tonks-Girardeau gas or a Bose-Hubbard model.  

Specifically, we predict that two-polariton states manifest an interaction-induced localization [1], where the first polariton forms a standing wave in a finite array, that creates a potential well for a second polariton and vice versa. In case when the standing wave has multiple nodes, it drives topologically nontrivial edge states [2]. Contrary to the usual Aubry-André-Harper model, such edge states emerge solely from interactions of two photons with atoms. No external magnetic field, complex lattices or external modulations are required. Mixing between different standing waves results in highly irregular two-polariton states which can be viewed as an interaction-induced quantum chaos [3].  

[1] J.Zhong et al., “Photon-Mediated Localization in Two-Level Qubit Arrays”, Phys. Rev. Lett. 124, 093604 (2020).

[2] A.V. Poshakinskiy et al., “Quantum Hall phases emerging from atom-photon interactions”, npj Quantum Information 7, 34 (2021),

[3] A.V. Poshakinskiy, J.Zhong, A.N. Poddubny, Phys. Rev. Lett. 126, 203602 (2021).

Zoom:https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09  

Laser Defense Systems- Science Fiction Materializing

Laser technology has advanced rapidly from the invention of the laser in the 1960’s to the Mega-Watt lasers of the late 1980’s. Alongside the rapid technology development comes an expectation for laser defense systems which have long been a part of science fiction literature. Nevertheless, the latter have yet to be fielded, coining the popular joke that high power laser systems have been three years away from us, for three decades. Over the last few years, the technology has matured and the operational need for this innovative and game-changing defense system has increased making their entrance to the battlefield imminent.

This Seminar describes how these systems work and focuses on the technological breakthroughs that finally allows their realization- fiber laser power scaling via beam combining, beam focusing and pointing and real-time atmospheric turbulence disturbance correction.

Journal club

Zeptosecond birth time delay in molecular photoionization (Chen Mor)

Ultrafast science is a an ever evolving field, allowing atto-seconds (10^-18 seconds) measurement and control of matter. I will discuss a science paper by Sven Grundmann et al. , where measurements of photoionization in zepto-seconds (10^-21 seconds) scale were performed.Using an electron interferometric technique, Grundmann et al. report a birth time delay on the order of a few hundred zeptoseconds between two electron emissions from the two sides of molecular hydrogen, which is interpreted as the travel time of the photon across the molecule.This work shows great promise for further advancement in ultrafast measurements. SVEN GRUNDMANN et al., science

Full-field quantum optical coherence tomography (Elad Benjamin)

Hong-Ou-Mandel (HOM) interference, the bunching of indistinguishable photons at a beam splitter, is a staple of quantum optics and lies at the heart of many quantum sensing approaches. One such method is quantum optical coherence tomography (QOCT). Classical OCT utilizes low coherence light to preform optical sectioning of a reflective sample, thus allowing for improved resolution in the axial direction and greater depth penetration. Through the HOM effect, QOCT can achieve 2-fold improved axial resolution compared to OCT. Furthermore, it intrinsically negates some dispersion effects, allowing in principle for greater penetration depths. In this talk I will review both OCT and QOCT, and present a recent work from Ibarra-Borja et al. implementing full-field QOCT, thereby bringing us one step closer toward QOCT as a practical bioimaging technique.

[1] C.K. Hong, Z.Y. Ou, and L. Mandel, Phys. Rev. Lett. 59, 2044 (1987)

[2] M.B. Nasr, D.P. Goode, N. Nguyen, G.Rong, L. Yang, B.M. Reinhard, B.E.A. Saleh, and M.C. Teich, Opt. Commun. 282, 1154 (2009).

[3] Z. Ibarra-Borja, C. Sevilla-Gutierrez, R. Ramirez-Alarcon, H. Cruz-Ramirez, and A.B. U'Ren, Photonics Research 8, 51 (2020).

Interplay of machine learning and quantum physics: from ML-enhanced quantum dynamics to quantum machine learning

I will describe our work that explores how quantum physics can benefit from machine learning and how machine learning can benefit from quantum computing. The connection between quantum mechanics and machine learning is through kernels of reproducing kernel Hilbert spaces. I will describe an algorithm to construct kernels that yield Bayesian machine learning models capable of extrapolation in Hamiltonian parameter spaces. I will then show that this algorithm can be adapted for building optimal circuits of a gate-based quantum computer, yielding quantum kernels that outperform conventional classical kernels for small data machine learning tasks. If time permits, I will also show that a support vector machine with a quantum kernel can be designed to be BQP-complete.

Nonlinear Spectroscopy of Nanomaterials

Electric fields are frequently used to manipulate the electronic properties of nanostructured materials. Commonly, such fields split and bend the energy structure of crystalline solids which can, in turn, alter their optical properties, such as their fluorescence due to band-to-band transitions. Furthermore, electric fields can be used, in principle, to modify the crystal potential permanently–by a structural change, or temporarily–as a perturbation.

Here, two separate studies were carried out to characterize the influence of electric fields on quantum-confined semiconductor nanostructures. First, we identified a linear response of the fluorescence of metal halide perovskite nanowires to the presence of an external electric field, which we associate with the forming of an internal dipole. Interestingly, this system often acts as an electret–where the dipole orientation depends on the history of the applied field. The system was modeled using such an assumed built-in potential, providing an analytically derived description ofthenanowires’behavior by adaptation of the carrier dynamics equation.

Additional, nonlinear optics probing of structural changeshadn’tfound significant changes due to the induction of the dipole. In the other part, the possibility of a perturbation of the second-order nonlinear susceptibility in semiconductor nanoplatelets by electrical charging during the fluorescence‘blinking’time was explored. Such perturbation might induce fluctuations of the nonlinear susceptibility tensorx(2) and of dependent processes such as second-harmonic generation (SHG). In order to reveal if such a correlation exists between fluorescence and nonlinear scattering, simultaneous detection of photoluminescence and SHG was conducted on single nanoplatelets placed on fabricated substrates having negligible surface SHG. Our finding shows the absence of a statistically significant correlation between the two mechanisms.

Hybrid seminar - physical seminar at Weismann seminar room A, virtual at - https://weizmann.zoom.us/j/94442528193?pwd=Nm1PZzVzR2w0bGE0OTZ5NzRmRDY5dz09

Imaging with scattered light: using speckles to see deeper and sharper

Scattering of light in complex samples, such as biological tissue, renders most samples opaque to conventional optical imaging techniques, a problem of great practical importance [1].  

However, although random, scattering of coherent light is deterministic, and possess inherent correlations that are maintained even after multiple scattering events. These allow physical correction of scattering [2], and computational reconstruction of diffraction-limited images through visually opaque samples and around corners [3], combining light and sound [4,5]. I will present the fundamental principles and limitations of the novel approaches that aim at undoing random scattering. If time permits, I will present how the same principles can also be employed to realize miniature lensless endoscopes [6].  

References

[1] Z. Merali, Optics: Super vision, Nature 518, 158 (2015).

[2] T. Yeminy, O. Katz, Guidestar-free image-guided wavefront shaping, Science Advances, 7, 21 (2021).

[3] O. Katz et al. Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations. Nature photonics, 8(10), 784-790 (2014).

[4] E. Hojman et al. Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery, Optics Express 25 (5), 4875-4886 (2016).

[5] M. Rosenfeld, D. Doktofsky, G. Weinberg, Y. Li, L. Tian, O. Katz, Acousto-optic Ptychography, Optica, (2021).

[6] W. Choi et al. Fourier holographic endoscopy for label-free imaging through a narrow and curved passage, arXiv:2010.11776 (2020).

journal club

Understanding the Berry phase – a bridge between pendulums to solid state physics (Lior Faeyrman)

The Berry phase, generalized by Sir Michael Berry [1], is canonically taught as a phase that appears due to an adiabatic evolution in a quantum system, avoiding the profound connection to geometry and classical mechanics. In this talk, I would like to try to give an intuition to the Berry phase in solid state physics through the help of a classical analog – the Foucault pendulum [2]. By understanding how the Berry phase is manifest in a simple classical example, one can then gain useful intuition and insights for the more abstract solid state case.

[1] Berry, M. V., 1984, Proc. R. Soc. London, Ser. A 392, 45.

[2] Jens von Bergmann, HsingChi von Bergmann ,” Foucault pendulum through basic geometry”, American Journal of Physics 75, 888 (2007); https://doi.org/10.1119/1.2757623  

Purcell-enhanced dipolar interactions in nanostructures (Inbar Shani)

Skljarow, A., Kübler, H., Adams, C. S., Pfau, T., Löw, R., & Alaeian, H. (2021). Purcell-enhanced dipolar interactions in nanostructures. arXiv preprint arXiv:2112.11175.
Strong light-induced interactions between atoms are known to cause nonlinearities at a few-photon level, which are crucial for applications in quantum information processing. Compared to free space, the scattering and the light-induced dipolar interaction of atoms can be enhanced by a dielectric environment. For this Purcell effect, either a cavity or a waveguide can be used. By combining the high densities achievable in thermal atomic vapors with an efficient coupling to a slot waveguide, one can exhibit repulsive interactions that are further enhanced by a factor of 8. This enhancement may pave the way towards a robust scalable platform for quantum nonlinear optics and all-optical quantum information processing at room temperature.

Atoms in lattices, cavities and tweezers

I will present two recent results from my laboratory where we use ultracold atoms to explore various aspects of quantum science.  In the first, we study the evolution and transport of atoms in two-dimensional honeycomb lattices.  We reveal how parallel transport through band touching points leads to non-Abelian non-holonomy that characterizes the geometric singularity at the band touching point, and also move toward studying flat-band physics in excited bands of the lattice.  In the second, we demonstrate the use of high-finesse optical cavities to perform rapid, high-fidelity measurements of the state of a single-atom optical tweezer trap, with important applications to the use of tweezer arrays for quantum simulation and computation.  I will wrap up by presenting some ideas about the potential role of electromagnetic vacuum fluctuations as a catalyst for photochemistry, and about producing ultracold gases from a new family of elements.

Seeing life in a new light

The progress of biomedical sciences depends on the availability of advanced instrumentation and imaging tools capable of attaining the state of biological systems in vivo without using exogenous markers. Mechanical forces and local elasticity play a central role in understanding physical interactions in all living systems. We demonstrate a novel way to image microscopic viscoelastic properties of biological systems using Brillouin microspectroscopy [1]. In my talk, I will discuss the ways how an old spectroscopic tool can be used for real time microscopic imaging [2-3] and provide possible solutions to long standing problems in Life Sciences and Medicine [4-6].

References

[1] Zh. Meng, A. Traverso, C. Ballmann, M. Troyanova-Wood, and V. V. Yakovlev, “Seeing cells in a new light: a renaissance of Brillouin spectroscopy,” Advances in Optics and Photonics 8(2), 300-327 (2016).

[2] Zh. Meng, S. C. Bustamante-Lopez, K. E. Meissner and V. V. Yakovlev, “Subcellular imaging of mechanical and chemical properties using Brillouin microspectroscopy,” Journal of Biophotonics 9(3), 201-207 (2016).

[3] C. W. Ballmann, Zh. Meng, A. J. Traverso, M. O. Scully, and V. V. Yakovlev “Impulsive Brillouin microscopy,” Optica 4(1), 124-128 (2017).

[4] Zh. Meng, T. Thakur, C. Chitrakar, M. K. Jaiswal, A. K. Gaharwar, and V. V. Yakovlev, “Assessment of local heterogeneity in mechanical properties of a bulk hydrogel network,” ACS Nano 11(8), 7690–7696 (2017).

[5] M. Troyanova-Wood, Zh. Meng, and V. V. Yakovlev, “Differentiating melanoma and healthy tissues based on elasticity-specific Brillouin microspectroscopy,” Biomedical Optics Express 10(4), 1774-1781 (2019).

[6] D. Akilbekova, V. Ogay, T. Yakupov, M. Sarsenova, B. Umbayev, A. Nurakhmetov, K. Tazhin, V. V. Yakovlev, Zh. Utegulov, “Brillouin spectroscopy and radiography for assessment of viscoelastic and regenerative properties of mammalian bones,” Journal of Biomedical Optics 23(9), 097004 (2018).

Optomechanics and momentum transfers in inhomogeneous ultra-cold gases

The momentum of light in a medium and the mechanisms of momentum transfer between light and dielectrics have long been the topic of controversies and confusion. We will discuss the problem of momentum transfers that follow the refraction and the reflection of light by inhomogeneous ensembles of ultra-cold atoms.
As a correction to a paper recently published, we show experimentally and theoretically that the refraction of light rays by a dilute gas does not entail momentum transfers to first order in the light-atom coupling coefficient. We then study the reflection of light by a dilute cloud and measure the force that acts on the atoms as a result. We show how resulting momentum transfers can be used to probe the dynamic of matter-wave gratings in Bose-Einstein condensates.  

Special seminar – note the time

Hybrid seminar – In Weismann auditorium and zoom - https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Journal club

Diffractive Focusing and guiding of waves using slits (Amit Pando)

The diffraction of waves by slits has been studied for centuries, from light waves to more recently, matter waves. While intuition might suggest that a wave passing through a slit will expand, it has recently been demonstrated that the wave actually focuses before expanding. I will present this mechanism, as well as a work in which the effects of such diffractive focusing have been further manipulated in order to create diffractive waveguides[1]: Periodic arrays of slits can be used to guide waves over a long distance with comparable energy losses to refractive waveguides. This has been demonstrated for both plasmonic waves and surface gravity water waves, but could be used for any wave which can be effectively blocked by such slits.

[1] Weisman, D., Carmesin, C. M., Rozenman, G. G., Efremov, M. A., Shemer, L., Schleich, W. P., & Arie, A. (2021). Diffractive guiding of waves by a periodic array of slits. Physical Review Letters, 127(1), 014303.

Spin Quantum Heat Engine Quantified by Quantum Steering (Jonathan Wengrowicz)

Following the rising interest in quantum information science, the extension of a heat engine to the quantum regime by exploring microscopic quantum systems has seen a boom of interest in the last decade. Although quantum coherence in the quantum system of the working medium has been investigated to play a nontrivial role, a complete understanding of the intrinsic quantum advantage of quantum heat engines remains elusive. We experimentally demonstrate that the quantum correlation between the working medium and the thermal bath is critical for the quantum advantage of a quantum Szilárd engine, where quantum coherence in the working medium is naturally excluded. By quantifying the nonclassical correlation through quantum steering, we reveal that the heat engine is quantum when the demon can truly steer the working medium. The average work obtained by taking different ways of work extraction on the working medium can be used to verify the real quantum Szilárd engine.

Journal club

Anyonic-parity-time symmetry in complex-coupled lasers (Sagie Gadasi)

Non-Hermitian Hamiltonians play an important role in many branches of physics, from quantum mechanics to acoustics. In particular, the realization of PT, and more recently – anti-PT symmetries in optical systems has proved to be of great value from both the fundamental as well as the practical perspectives. Both the PT and anti-PT symmetries are specific instances of a broader class known as anyonic-PT symmetry, where the Hamiltonian and the PT operator satisfy a generalized commutation relation.

In this work we study this novel symmetry and demonstrate it experimentally in a coupled lasers system. This is achieved using complex coupling – of mixed dispersive and dissipative nature, which allows unprecedented control on the location in parameter space where the symmetry and symmetry-breaking occur. Moreover, tuning the coupling in the same physical system, allows us to realize the more familiar special cases of PT and anti-PT symmetries. In a more general perspective, we present and experimentally validate a new relation between laser synchronization and the symmetry of the underlying non-Hermitian Hamiltonian.

Reference: [1] G. Arwas, S. Gadasi, I. Gershenzon, A. Friesem, N. Davidson, and O. Raz, Anyonic Parity-Time Symmetric Laser, ArXiv:2103.15359v1 [Physics] (2021).

Realizing a topological insulator with coupled vertical-cavity lasers (Eran Bernstein)

Topological insulator lasers are arrays of semiconductor lasers that exploit fundamental features of topology to force all emitters to act as a single coherent laser. I will present a work realizing such a topological insulator laser in an array of vertical-cavity surface-emitting lasers (VCSELs)[1]. I will focus on the topological properties of the scheme that is demonstrated for coupling lasers, and how it generates protected edge states and robust phase locking. This is an example for the generality of topological insulators to non-electronic wave systems such as photonics, cold atoms, and acoustics.

[1] Alex Dikopoltsev, Tristan H. Harder, Eran Lustig, Oleg A. Egorov, Johannes Beierlein, Adriana Wolf, Yaakov Lumer, Monika Emmerling, Christian Schneider, Sven Höfling, Mordechai Segev, Sebastian Klembt. Topological insulator vertical-cavity laser array. Science, 2021; 373 (6562): 1514 DOI: https://doi.org/10.1126/science.abj2232

Journal club

Photon storage in ordered atomic arrays (Yakov Solomons)

Quantum memory is an essential ingredient in the field of quantum information processing. One of the promising approaches for quantum memory is photon storage, in which an optical state is reversibly converted to an atomic excitation.In this talk, I will present our recent work on photon storage in ordered atomic arrays. These arrays, which are characterized by collective coupling to light [1], suppress the light emission into undesirable directions. This property makes the ordered arrays an excellent platform for efficient light storage [2].

[1] E. Shahmoon, D. S. Wild, M. D. Lukin, and S. F. Yelin, Cooperative resonances in light scattering from two-dimensional atomic arrays, Physical Review Letters 118, 113601 (2017).

[2] M. Manzoni, M. Moreno-Cardoner, A. Asenjo-Garcia, J. V. Porto, A. V. Gorshkov, and D. Chang, Optimization of photon storage fidelity in ordered atomic arrays, New Journal of Physics 20, 083048 (2018).

Description and first application of a new technique to measure the gravitational mass of antihydrogen (Raz Boaz)

Physicists have long wondered whether the  gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime.

https://www.nature.com/articles/ncomms2787

Free-electron interaction with engineered plasmonic fields

The interaction of free electrons with light has been a continuous source of new discoveries and technologies, ranging from medical imaging [1] and microscopy [2] techniques to bright, ultrafast x-ray sources [3] and particle accelerators [4]. In recent years, particular attention was devoted to such interactions occurring in platforms with a strong near-field component [5,6], revealing novel ways to manipulate the wavefunction of free electrons in an inherently quantum-mechanical way. As such, it is clear that precise control over the near-field distribution can enable new physical observations and technological capabilities, making it the main focus of our work.

By passively and actively controlling the transverse distribution of a plasmonic field, we generated various high-quality electron probability distributions and shifted between them, while altering the resulting pattern through post-selection [7]. By employing a hybrid photonic-plasmonic waveguide design to control the longitudinal near-field distribution, 2D Cherenkov radiation and its quantized nature were observed for the first time, along with a record-high free-electron - photon coupling strength [8]. Our investigation pushes the limit of free-electron interactions with light to new regimes, establishing free electrons as an alternative route for quantum optics and making a significant step towards the long-standing goal of arbitrary spatial modulation of electrons.

[1] A. Ruggiero et al, J. Nucl. med. 51, 1123-1130 (2010)

[2] B. Barwick et al, Nature 462, 902–906 (2009)

[3] J. Duris et al, Nat. Photon. 14, 30–36 (2020)

[4] E. A. Peralta et al, Nature 503, 91–94 (2013)

[5] A. Feist et al, Nature 521, 200–203 (2015)

[6] G. M. Vanacore et al, Nat. Mater. 18, 573–579 (2019)

[7] S. Tsesses et al, CLEO: QELS_Fundamental Science, FM1L. 2 (2021); Manuscript under review

[8] Y. Adiv et al, CLEO: QELS_Fundamental Science, FM1L. 6 (2021); Manuscript under review  

Journal club

The realization of the supersolid and its study (Gavriel Fleurov)

Two new phases, quantum droplets and supersolids, have been realized in several labs during the several years. These states require a delicate balance between repulsive and attractive forces, currently achieved in dipolar gases and Bose-Bose mixtures. This talk will focus on an exemplary study of the supersolid [1]. The authors employed two-photon Bragg spectroscopy as a probe of density modulation and coherent and incoherent phase variations. The spectroscopy is conducted in tandem with a tuning of the interaction strength to drive the system from a Bose-Einstein condensate to a supersolid and then insulating droplets. I will present their results, discuss the physics that enables these states, and review related works.

[1] D. Petter, A. Patscheider, G. Natale, M. J. Mark, M. A. Baranov, R. van Bijnen, S. M. Roccuzzo, A. Recati, B. Blakie, D. Baillie, L. Chomaz, and F. Ferlaino. Bragg scattering of an ultracold dipolar gas across the phase transition from Bose-Einstein condensate to supersolid in the free-particle regime. Physical Review A, 104(1):L011302, July 2021.

Dancing atomic qubits (Lee Drori)

In order to engineer a scalable quantum processor, it is important to have parallel and programmable operations between desired qubits. However, in most state-of-the-art approaches, the qubits interact locally and are constrained by their physical location.

In my talk, I will present a recent paper [1] where coherent transport of atoms in a tweezer array was used to demonstrate a quantum processor with dynamic, nonlocal connectivity. This ability was used in between layers of single and two-qubit operations to generate a variety entangled graph states. To achieve the wonderful results described in the paper, the authors had to solve a lot of technical issues, which results in a long and interesting methods section. In my talk I will mainly focus on the technical aspects of the work. Additionally, the work greatly builds upon a previous paper by the same group [2], and an interesting new way to generate high frequency AM modulation, out of PM modulation [3].

[1]: Bluvstein, Dolev, et al. "A quantum processor based on coherent transport of entangled atom arrays." arXiv preprint arXiv:2112.03923 (2021).

[2] Levine, H. et al. Parallel Implementation of High-Fidelity Multiqubit Gates with Neutral Atoms. Physical Review Letters 123, 170503 (2019).

[3] Levine, H. et al. Dispersive optics for scalable Raman driving of hyperfine qubits (2021). arXiv:2110.14645.

Journal club

Solid-state spin qubits in diamond light-matter interface for quantum networking

Among the various candidates, the tin-vacancy center (SnV) is exciting due to its large spin-orbit coupling that offers protection against dephasing. In this talk, I will present a recent paper that demonstrates coherent control of the SnV spin qubit via an all-optical scheme. The authors drive Rabi oscillations in the spin-qubit and measure its dephasing and coherence time. In the talk, I will discuss this specific platform, compare them to similar platforms, and the potential of this spin-qubit for several applications.

R. Debroux, C. P. Michaels, C. M. Purser, N. Wan, M. E. Trusheim, J. Arjona Martínez, R. A. Parker, A. M. Stramma, K. C. Chen, L. de Santis, E. M. Alexeev, A. C. Ferrari, D. Englund, D. A. Gangloff, and M. Atatüre, Quantum Control of the Tin-Vacancy Spin Qubit in Diamond, Phys. Rev. X 11, 41041 (2021).

New methods in super-resolution confocal microscopy

The seminar will be held in ZOOM due to COVID regulations.

ZOOM link - https://weizmann.zoom.us/j/94818342606?pwd=RmNSRXJmeUNYNzRsblNxN2ZManUvUT09

The Nobel Prize in chemistry acknowledged in 2014 major breakthroughs which gave birth to the field of super-resolution imaging and revolutionized life-sciences studies. At present, research continues to revolve around improving the performance of the optical microscope, in terms of image resolution and quality on one hand and ease of operation on the other.

In this talk I will present results from my PhD about developing novel imaging tools aimed to enhance the performance of the biologist’s standard confocal microscope, relying on measurement of photon correlations. These innovations include upgraded experimental apparatus and methods as well as advanced image reconstruction approaches.

Pulsed Ion Microscope to Probe Quantum Gases

The seminar will be held in ZOOM due to COVID regulations.

ZOOM link - https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

For any microscope to be useful, it must have a resolving power sufficient to image the features of interest. For quantum gases, these features, which include atoms and their spatial order, typically have submicron length scales. Optical quantum gas microscopes offer the possibility to image strongly interacting atoms loaded into optical lattices with a submicron resolution. In this talk, I will present a recent paper reporting a high-resolution ion microscope that can be used as a powerful experimental tool to investigate quantum gases. In this paper, they also demonstrate a pulsed operation mode of the ion microscope, enabling 3D imaging and allowing for the study of ionic impurities and Rydberg physics.

C. Veit, N. Zuber, O. A. Herrera-Sancho, V. S. V. Anasuri, T. Schmid, F. Meinert, R. Löw, and T. Pfau , “Pulsed ion microscope to probe quantum gases,” Phys. Rev. X 11, 011036 (2021).

Nanophotonic structure-mediated free-electron acceleration and manipulation in the classical and quantum regimes

The seminar will be held in ZOOM due to COVID regulations.

ZOOM link - https://weizmann.zoom.us/j/99871493260?pwd=K01BTGkwVWFRUzFQQjBTb2VIZ01xdz09

Dielectric laser accelerators (DLA) are, fundamentally, the interaction of photons with free electrons, where energy and momentum conservation are satisfied by mediation of a nanostructure. In this scheme, the photonic nanostructure induces near-fields, which transfer energy from the photon to the electron via the inverse-Smith-Purcell effect [1,2]. Research in this direction is a wonderful opportunity to engage in multi-disciplinary science, because it directly involves accelerator physics, quantum physics, electron microscopy, ultrafast lasers, near-field optics, and nanofabrication. There is great potential for DLA to provide ground-breaking applications, as it is the only technology promising to miniaturize particle accelerators down to the chip-scale. This is because dielectric materials allow using an order of magnitude larger electric fields, relative to metallic radiofrequency (RF) acceleration cavities. Further, modern ultrafast lasers are perfectly poised to induce these high fields, and have additional advantages over RF technology, including high repetition rates, femtosecond temporal period, and inherent phase-locking to the electron pulse, when the latter is generated by the same laser. This fundamental interaction can also be used to study and demonstrate quantum photon-electron interaction. Photon-induced electron-microscopy (PINEM), first observed in 2009 and intended for applications in microscopy [3], has since evolved to be a fruitful source of photon-electron quantum phenomena. In particular, the free electron’s energy spectrum can be measured and shown to have discrete energy peaks, spaced with the interacting photon energy, and correlated to the number of photon exchanges that took place during the interaction. In this seminar, I will introduce you to the field of DLA. I will discuss the general prospects of DLA beyond its initial goal - electron acceleration - and towards the rich physics of photon-electron interaction with nanostructures. Our recently-published demonstration of free-electron transport in a nanophotonic structure will be presented [4], along with results from our recently-submitted work on measurements of photon-energy-resolved energy peaks, which were measured in a scanning electron microscope for the first time [5].

1. J. Breuer and P. Hommelhoff, "Laser-based acceleration of nonrelativistic electrons at a dielectric structure," Phys. Rev. Lett. 111, (2013).
2. E. A. Peralta, K. Soong, R. J. England, E. R. Colby, Z. Wu, B. Montazeri, C. McGuinness, J. McNeur, K. J. Leedle, D. Walz, E. B. Sozer, B. Cowan, B. Schwartz, G. Travish, and R. L. Byer, "Demonstration of electron acceleration in a laser-driven dielectric microstructure," Nature 503, 91–94 (2013).
3. B. Barwick, D. J. Flannigan, and A. H. Zewail, "Photon-induced near-field electron microscopy," Nature 462, 902 (2009).
4. R. Shiloh, J. Illmer, T. Chlouba, P. Yousefi, N. Schönenberger, U. Niedermayer, A. Mittelbach, and P. Hommelhoff, "Electron phase space control in photonic chip-based particle acceleration," Nature 592, 498–502 (2021).
5. R. Shiloh, T. Chlouba, and P. Hommelhoff, "Quantum-coherent light-electron interaction in an SEM," Submitted arxiv.org/abs/2110.00764 (2021).

Non-Newtonian Gravity and Neutrality of Matter Searches with Levitated Test Masses

Note the special date and time! The universal law of gravitation has undergone stringent tests for many decades over a significant range of length scales, from atomic to planetary. Of particular interest is the short distance regime, where modifications to Newtonian gravity may arise from axion-like particles or extra dimensions. We have constructed an ultra-sensitive force sensor based on optically-levitated micro-spheres with a force sensitivity of 10^-16 N/sqrt(Hz) to investigate forces that couple to mass with a characteristic scale of ~ 10um. In this talk, I will present the first investigation of the inverse-square law using an optically levitated test mass, along with the technical development that preceded it.

Then I will present a recent precision measurement conducted with the same setup in which we demonstrate, for the first time, a technique capable of using data to model minute electromagnetic forces, hence eliminating the back-grounds limiting many measurements, including short-range forces. In addition, this approach allows precision metrology of the dielectric properties of levitated microspheres. This process results in an unprecedented charge sensitivity of 3.3*10^-5 e for a macroscopic object. As a specific example, we apply the technique to test the observation that the proton charge is equal in magnitude to that of the electron.

The seminar will be held over Zoom- Link: https://weizmann.zoom.us/j/97240339317?pwd=SlMxZGVUZ0J6d0svUlpqV2p3NjlpUT09 Meeting ID: 972 4033 9317 Password: 356902

Quantum inference: unraveling “which pathway?” information

Note the special date and time!

Quantum systems are remarkably sensitive to changes in their environment. This renders them extraordinary probes for sensing applications. In contrast to classical probes, they undergo transitions upon coupling that encode trajectory dependent quantum information in their statistics. Decoding this information requires a new set of inference methodologies, such as the one we introduce here.

Entangled photon pairs have inspired a myriad of quantum-enhanced metrology platforms, which outperform their classical counterparts. However, the role of photon exchange-phase and degree of distinguishability have not yet been utilized in quantum-enhanced applications. We show that when a two-photon wave-function is coupled to matter, it is encoded with “which pathway?” information even at a low degree of entanglement. An interferometric exchange-phase-cycling protocol is developed, revealing phase-sensitive information for each interaction history individually. Moreover, we find that quantum-light multimode interferometry introduces a new set of time variables that enable time-resolved signals, unbound by uncertainty to the inverse bandwidth of the wave-packet. We illustrate our findings on an exciton model-system and discuss future applications.  

Time 13:10-14:10

Engineering quantum processors and quantum networks atom-by-atom

Engineering quantum processors and quantum networks atom-by-atom

Reconfigurable arrays of neutral atoms are an exciting new platform to study quantum many-body phenomena and quantum information protocols. Their excellent coherence combined with programmable Rydberg interactions have led to intriguing observations such as quantum phase transitions, the discovery of quantum many-body scars, and the recent realization of a topological spin liquid phase.

Here, I will introduce new methods for controlling and measuring atom arrays that open up new directions in quantum state control, quantum feedback, and many-body physics. First, I will introduce a dual species atomic array in which the second atomic species can be used to measure and control the primary species. This will lead to the possibility of performing quantum nondemolition measurements and new ways of engineering large, entangled states on these arrays. Furthermore, prospects of studying open systems with engineered environments will be discussed.

An alternative, hybrid approach for engineering interactions and scaling these quantum systems is the coupling of atoms to nanophotonic structures in which photons mediate interactions between atoms. Such a system can function as the building block of a large-scale quantum network. In this context, I will present quantum network node architectures that are capable of long-distance entanglement distribution at telecom wavelengths.

Phase transitions with coupled lasers

Phase transitions with coupled lasers

During this talk, I will present my results obtained during my PhD on how coupled lasers can be used for solving minimization problems, investigating phase transitions and spin systems,imaging through scattering media, controlling modes interactions, high-resolution beam shaping and more.I will also present new coupling schemes for efficient phase locking of hundreds of lasers.

All-optical noise spectroscopy of solid-state spin qubits

The development of spin qubits with long coherence times for quantum information processing requires sources of spin noise to be identified and minimized. Although microwave-based spin control is typically used to extract the noise spectrum, this becomes infeasible when high frequency noise components are stronger than the available microwave power. Here, we introduce an all-optical approach for noise spectroscopy of spin qubits. Our approach is based on Raman spin rotation for the application of coherent control pulse sequences inspired by nuclear magnetic resonance spectroscopy. By analyzing the resulting spin dynamics, we extract the noise spectrum of a single electron confined in a quantum dot, which represents its hyperfine interaction with an ensemble of nuclear spins broadened by strain. Our Raman-based analysis provides insights for extending the coherence times and predicts the dynamics of optically-active spin systems. Such understanding is crucial for the development of qubits with long coherence times toward novel applications in quantum information processing and quantum sensing.

The possibility of novel spatial and temporal interaction channels

The resolution of optical microscopy in the far field is on the order of the wavelength with several recent advances that utilize fluorophores. Electromagnetic fields interact with atoms and molecules in the far field only via the dipole moment due to the size difference between the wavelength and atoms and molecules. Physical systems can scatter and absorb strongly coherent inputs at certain frequencies. Here we show that a setup of a resonant spherical shell can generate the time reversal of the field emitted in an atomic or molecular multipole transition and that this setup exhibits an infinite asymptotic degeneracy of its modes. Then, by treating the quantum current as classical and utilizing time reversal, we consider the possibility that when placing an atom or molecule at the origin, many spatial interaction channels will come into play, which may enable us to resolve atoms and molecules with atomic resolution in the far field. In addition, we present a novel class of temporal interaction channels at both real and virtual frequencies with experimental results, and suggest a conversion mechanism between them. Finally, we analyze the interaction between electrodynamic fields and vibrations in helical structures, with potential implications in long range interactions between the microtubule and the surrounding molecules and coupling between distant molecules via the microtubule. If time will allow, we will describe recent efforts to discover a drug for Covid-19 using a free energy calculation method.

From Hanbury-Brown and Twiss to photon correlation enhanced spectroscopy and microscopy

When Hanbury-Brown and Twiss proposed to use photon correlations for stellar interferometry in 1954 the idea was received with great skepticism. Yet, the use of photon correlations for various uses, from identification of quantum emitters to emitter counting grew over the years. In the talk, I will describe some of our efforts in using HBT correlations and their derivatives in superresolution microscopy and in advanced spectroscopy of quantum emitters, as well as the technological advances enabling this.