PhD positions

Laser plasma accelerators allow to produce the most extreme electric fields of TV/m that are revolutionarized accelerator physics. A critical limitation of laser driven Wakefield concept is that the velocity of the wave is getting slower when the trapped electrons are getting relativistic enough. To avoid such limitation we develop with spatio temporal coupling and special optic a solution that leads to luminal, sub or super- luminal wake of major interest for getting significant energy gain.

The purposes of the thesis is to explore all the benefits of such original approach using the unique 100 TW laser system at WIS. 

We investigate phase locking of large arrays of coupled lasers in a modified degenerate cavity. We show that the minimal loss lasing solution is mapped to the ground state of an XY spin Hamiltonian with the same coupling matrix provided the intensity of all the lasers is uniform. We study the probability to obtain this ground state for various coupling schemes, system parameters and topological constrains. We demonstrate the effect of crowd synchrony with a sharp transition into an ordered state above a critical number of coupled lasers. Finally, we present recent results demonstrating the ability of our system to solve related problems such as phase retrieval, imaging through scattering medium and more.

In collaboration  with Roee Ozeri we form Bose Einstein condensates of rubidium 87 atoms, quantum degenerated fermionic gas of potassium 40 atoms, and their mixtures using laser cooling and evaporative cooling in magnetic and far-detuned optical traps and study their properties. Such dilute quantum gases offer full control of external and internal degrees of freedom and variety of unique interrogation tools that enable precise studies of many body quantum systems.

By using magnetic Feshbach resonances we tune the system from weakly interacting where the it can be simply described by a macroscopic wave function to the strongly interacting  where highly correlated many body states can be generated and studied. We study and characterize the coherence, dynamics and elementary excitations of these dilute quantum gases using laser and microwave probes and study new type of an opto-mechanical force when they are illuminated with far-detuned uniform laser beam.

In collaboration  with Ofer Firstenberg recently started a new joint project on efficient coupling of neutral-atom tweezer arrays to light. On the theoretical side we are collaborating with Efi Shahmoon. We plan to extend Efi’s original ideas for strong coupling in atomic arrays in sub-wavelength optical lattices (recently verified experimentally by Immanuel Bloch) to the emerging and promising field of quantum simulators with Rydberg atoms in tweezer arrays, where the spacing between the atoms is larger than the wavelength. The challenge to achieved strong coupling to light in such large-spacing arrays emerges from the existence of many diffraction orders that cannot be controlled.

Our proposed scheme to overcome this challenge is based on two supplementary efforts: first we will reduce the spacing between neighboring atoms in the array to <1.5 microns, by suppressing the mutual interferences that limit this distance to >3 microns in most state of the art demonstrations. Such spacing reduction will reduce the non-vanishing diffraction orders from the periodic array from many tens to only few. Next we will incorporate the tweezer array inside a medium finesse optical cavity that will enhance the zero diffraction order as compared to the others so as to ensure strong coupling to it.

We plan to achieve strong coupling to light, show efficient transfer of coherence and quantum states from the array onto a single radiation mode and then use it to demonstrate and study novel schemes for quantum simulators within the atomic tweezer array as well as quantum coupling between tweezer arrays for “scalable” quantum computer based on Rydberg induced gates.

Hawking radiation - the emission of quantum particles at the event horizon of a black hole - connects gravity with quantum mechanics and thermodynamics; the Bekenstein-Hawking entropy has been the benchmark for potential quantum theories of gravity. But Hawking radiation has never been observed in astronomy, only in laboratory analogues including our experiment, and the chances of ever observing it in space are astronomically small. The energy of Hawking radiation must come from the gravitational field around the black hole, but how field quanta generate Hawking quanta has been unknown. We are working on getting experimental and theoretical evidence for the process that generates Hawking radiation in a fibre-optical analogue of the event horizon. There, as in gravity, it has been believed that Hawking radiation comes from a complicated, cascaded process; here we have found a simple, direct process and measured its backreaction on the field. Our findings suggest an equally direct process for other laboratory analogues and perhaps also for gravitational fields, shedding light on how black holes might radiate.