Path and phase determination for an interfering photon with orbital angular momentum
M. Kolar, T. Opatrny and G. Kurizki, Opt. Lett. 33, 67(2008).
A polarized photon with well-defined orbital angular momentum that emerges from a Mach - Zehnder interferometer (MZI) is shown to seemingly circumvent wave-particle duality constraints. For certain phase differences between the MZI arms, this pattern yields both reliable which-path information and high phase sensitivity. (c) 2007 Optical Society of America.Path-phase duality with intraparticle translational-internal entanglement
M. Kolar, T. Opatrny, N. Bar-Gill, N. Erez and G. Kurizki, N. J. Phys. 9, (2007).
The aim of this paper is to revisit the implications of complementarity when we inject into a Mach Zehnder interferometer particles with internal structure, prepared in special translational-internal entangled (TIE) intraparticle states. This correlation causes the path distinguishability to be interferometric phase-dependent in contrast to the standard case, where distinguishability depends on some external parameters ( not interferometric phase). We show that such a TIE state permits us to detect small phase shifts along with almost perfect path distinguishability, beyond the constraints imposed by complementarity on simultaneous which-way and which-phase measurements for cases when distinguishability is uncoupled to interferometric phase.Free matter wavepacket teleportation via cold-molecule dynamics
L. Fisch and G. Kurizki, Europhys. Lett. 75, 847(2006).
We explore the feasibility of creating a translationally entangled state for massive particles, and its use for matter wave teleportation by means of cold-molecule Raman dissociation and association in optical traps.Signatures of Strong Momentum Localization via Entanglement of Translational and Internal States
N. Bar-Gill and G. Kurizki, Phys. Rev. Lett. 97, 230402 (2006).
We show that atoms or molecules subject to fields that couple their internal and translational (momentum) states may undergo a crossover from randomization (diffusion) to strong localization (sharpening) of their momentum distribution. The predicted crossover should be manifest by a drastic change of the interference pattern as a function of the coupling fields.Preventing multipartite disentanglement by local modulations.
G. Gordon and G. Kurizki, Phys Rev Lett 97, 110503(2006).
An entangled multipartite system coupled to a zero-temperature bath undergoes rapid disentanglement in many realistic scenarios due to local, symmetry-breaking differences in the particle-bath couplings. We show that locally controlled perturbations, addressing each particle individually, can impose a symmetry allowing the existence of decoherence-free multipartite entangled systems.Free matter wavepacket teleportation via cold-molecule dynamics
L. Fisch and G. Kurizki, Europhys. Lett. 75 847 (2006)
We explore the feasibility of creating a translationally entangled state for massive particles, and its use for matter wave teleportation by means of cold-molecule Raman dissociation and association in optical traps.Preventing Multipartite Disentanglement by Local Modulations
G. Gordon and G. Kurizki, Phys. Rev. Lett. 97, 110503 (2006).
An entangled multipartite system coupled to a zero-temperature bath undergoes rapid disentanglement in many realistic scenarios due to local, symmetry-breaking differences in the particle-bath couplings. We show that locally controlled perturbations, addressing each particle individually, can impose a symmetry allowing the existence of decoherence-free multipartite entangled systems.Translational Entanglement by Collisions and Half-Collisions
L. Fisch, A. Tal and G. Kurizki, Int. J. Mod. Phys. B 20, 1648 (2006).
To date, the translationally-entangled state originally proposed by Einstein, Podolsky and Rosen (EPR) in 1935 has not been experimentally realized for massive particles. Opatrný and Kurizki [Phys. Rev. Lett. 86, 3180 (2000)] have suggested the creation of a position- and momentum-correlated, i.e., translationally-entangled, pair of particles approximating the EPR state by dissociation of cold diatomic molecules, and further manipulation of the EPR pair effecting matter-wave teleportation. Here we aim at setting the principles of and quantifying translational entanglement by collisions and half-collisions. In collisions, the resonance width s and the initial phase-space distributions are shown to determine the degree of post-collisional momentum entanglement. Half-collisions (dissociation) are shown to yield different types of approximate EPR states. We analyse a feasible realization of translational EPR entanglement and teleportation via cold-molecule Raman dissociation and subsequent collisions, resolving both practical and conceptual difficulties it has faced so far: How to avoid entanglement loss due to the wavepacket spreading of the dissociation fragments? How to measure both position and momentum correlations of the dissociation fragments with sufficient accuracy to verify their EPR correlations? How to reliably perform two-particle (Bell) position and momentum measurements on one of the fragments and the wavepacket to be teleported?Quantum computer with dipole-dipole interacting two-level systems
D. Petrosyan and G. Kurizki, Quant. Inf. & Comp. 6, 1 (2006), quant-ph/0411188.
A scalable, high-performance quantum processor can be implemented using near-resonant dipole-dipole interacting dopants in a solid state host. In this scheme, the qubits are represented by ground and subradiant states of effective dimers formed by pairs of closely spaced two-level systems, while the two-qubit entanglement either relies on the coherent excitation exchange between the dimers or is mediated by external laser fields.Long-range interactions and entanglement of slow single-photon pulses
I. Friedler, D. Petrosyan, M. Fleischhauer and G. Kurizki, Phys. Rev. A 72, 043803 (2005).
We show that very large nonlocal nonlinear interactions between pairs of colliding slow-light pulses can be realized in atomic vapors in the regime of electromagnetically induced transparency. These nonlinearities are mediated by strong, long-range dipole-dipole interactions between Rydberg states of the multilevel atoms in a ladder configuration. In contrast to previously studied schemes, this mechanism can yield a homogeneous conditional phase shift of
even for
weakly focused single-photon
pulses, thereby allowing a deterministic
realization of the
photonic phase gate.
Translational entanglement via collisions: How much quantum information is obtainable?
A. Tal and G. Kurizki, Phys. Rev. Lett. 94, 160503 (2005).
We study collisions mediated by finite-range potentials as a tool for generating translational entanglement between unbound particles or multipartite systems. The general analysis is applied to one-dimensional scattering, where resonances and the initial phase-space distribution are shown to determine the degree of postcollisional entanglement.Deterministic quantum logic with photons via optically induced photonic bandgaps
I. Friedler, G. Kurizki and D. Petrosyan, Phys. Rev. A 71, 023803 (2005) .
We study the giant Kerr nonlinear interaction between two ultraweak optical fields in which the cross-phase-modulation is not accompanied by spectral broadening of the interacting pulses. This regime is realizable in atomic vapors, when a weak probe pulse, upon propagating through the electromagnetically induced transparency (EIT) medium, interacts with a signal pulse that is dynamically trapped in a photonic band gap created by spatially periodic modulation of its EIT resonance. We find that large conditional phase shifts and entanglement between the signal and probe fields can be obtained with this scheme. The attainable phase shift, accompanied
by negligible
absorption and quantum noise, is shown to allow
a
high-fidelity realization of the
controlled-phase universal
logic gate between two single-photon pulses.
Position and Momentum Entanglement of Dipole-Dipole Interacting Atoms in Optical Lattices: The Einstein-Podolsky-Rosen Paradox on a Lattice
T. Opatrny, M. Kolar, G. Kurizki and B. Deb, Int. J. Quant. Info. 2, 305-321 (2004).
We study a possible realization of the position- and momentum-correlated atomic pairs that are confined to adjacent sites of two mutually shifted optical lattices and are entangled via laser-induced dipole-dipole interactions. The Einstein-Podolsky-Rosen (EPR) ``paradox'' [Phys. Rev. {\bf 47,} 777 (1935)] with translational variables is then modified by lattice-diffraction effects. This ``paradox'' can be verified to a high degree of accuracy in this scheme.