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Publications | Alex Retzker's Group

Publications

2007
A Retzker and Plenio, MB . 8/23/2007. Fast Cooling Of Trapped Ions Using The Dynamical Stark Shift. New Journal Of Physics, 9. . Publisher's Version
A laser cooling scheme for trapped ions is presented which is based on the fast dynamical Stark shift gate, described in (Jonathan et al 2000 Phys. Rev. A 62 042307). Since this cooling method does not contain an off resonant carrier transition, low final temperatures are achieved even in a traveling wave light field. The proposed method may operate in either pulsed or continuous mode and is also suitable for ion traps using microwave addressing in strong magnetic field gradients.
I Katz, Retzker, A, Straub, R, and Lifshitz, R. 7/26/2007. Signatures For A Classical To Quantum Transition Of A Driven Nonlinear Nanomechanical Resonator. Physical Review Letters, 99, 4. . Publisher's Version
We seek the first indications that a nanoelectromechanical system (NEMS) is entering the quantum domain as its mass and temperature are decreased. We find them by studying the transition from classical to quantum behavior of a driven nonlinear Duffing resonator. Numerical solutions of the equations of motion, operating in the bistable regime of the resonator, demonstrate that the quantum Wigner function gradually deviates from the corresponding classical phase-space probability density. These clear differences that develop due to nonlinearity can serve as experimental signatures, in the near future, that NEMS resonators are entering the quantum domain.
A Retzker, Solano, E, and Reznik, B. 2/13/2007. Tavis-Cummings Model And Collective Multiqubit Entanglement In Trapped Ions. Physical Review A, 75, 2. . Publisher's Version
We present a method of generating collective multiqubit entanglement via global addressing of an ion chain performing blue and red Tavis-Cummings interactions, where several qubits are coupled to a collective motional mode. We show that a wide family of Dicke states and irradiant states can be generated by single global laser pulses, unitarily or helped with suitable postselection techniques.
A Retzker, Plenio, MB , Simos, TE , and Maroulis, G. 2007. Fast Cooling Of Trapped Ions Using The Dynamical Stark Shift. Computation In Modern Science And Engineering Vol 2, Pts A And B, 2, Pp. 792-795. . Publisher's Version
A laser cooling scheme for trapped ions is presented which is based on the fast dynamical Stark shift gate, described in (Jonathan et al 2000 Phys. Rev. A 62 042307). Since this cooling method does not contain an off resonant carrier transition, low final temperatures are achieved even in a traveling wave light field. The proposed method may operate in either pulsed or continuous mode and is also suitable for ion traps using microwave addressing in strong magnetic field gradients.
2006
A Retzker, Aharonov, Y, Botero, A, Nussinov, S, and Reznik, B. 3/15/2006. Aharonov-Bohm Effect Without Closing A Loop. Physical Review A, 73, 3. . Publisher's Version
We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron-hole pairs. We discuss the relevance of such effects in “vacuum birefringence" in QED, and comment on their connection to other known effects.
L Vaidman, Erez, N, and Retzker, A. 2006. Another Look At Quantum Teleportation. International Journal Of Quantum Information, 4, 1, Pp. 197-208. . Publisher's Version
A dialog with Asher Peres regarding the meaning of quantum teleportation is briefly reviewed. The Braunstein–Kimble method for teleportation of light is analyzed in the language of quantum wave functions. A pictorial example of continuous variable teleportation is presented using computer simulation.
2005
B Reznik, Retzker, A, and Silman, J. 4/14/2005. Violating Bell'S Inequalities In Vacuum. Physical Review A, 71, 4. . Publisher's Version
We employ an approach wherein the ground state entanglement of a relativistic free scalar field is directly probed in a controlled manner. The approach consists of having a pair of initially nonentangled detectors locally interact with the vacuum for a finite duration T, such that the two detectors remain causally disconnected, and then analyzing the resulting detector mixed state. We show that the correlations between arbitrarily far-apart regions of the vacuum cannot be reproduced by a local hidden-variable model, and that as a function of the distance L between the regions, the entanglement decreases at a slower rate than ∼exp[−(L∕cT)3].
A Retzker, Cirac, JI , and Reznik, B. 2/9/2005. Detecting Vacuum Entanglement In A Linear Ion Trap. Physical Review Letters, 94, 5. . Publisher's Version
We propose and study a method for detecting ground-state entanglement in a chain of trapped ions. We show that the entanglement between single ions or groups of ions can be swapped to the internal levels of two ions by sending laser pulses that couple the internal and motional degrees of freedom. This allows us to entangle two ions without actually performing gate operations. A proof of principle of the effect can be realized with two trapped ions and is feasible with current technology.
2004
B Reznik, Retzker, A, and Silman, J. 7/6/2004. A Lower Bound On Ground State Entanglement Between Two Regions For A Free Field. Journal Of Modern Optics, 51, 6-7, Pp. 833-840. . Publisher's Version
In discrete models, such as spin chains, the entanglement between a pair of particles in a chain has been shown to vanish beyond a certain separation. In the continuum, a quantum field ⊘(x) at a point represents a single degree of freedom, thus at a region of finite size there are infinite separate degrees of freedom. We show that as a consequence, in contrast to discrete models, the ground state of a free, quantized and relativistic field exhibits entanglement between any pair of arbitrarily separated finite regions. We also provide a lower bound on the decay rate of the entanglement as a function of the separation length between the regions and briefly discuss the physical reasons behind this different behaviour of discrete and continuous systems.
2002
A Retzker and Shapiro, B. 2/2002. Infinite Range Correlations Of Intensity In Random Media. Pramana-Journal Of Physics, 58, 2, Pp. 225-231. . Publisher's Version
We study a new type of long-range correlations for waves propagating in a random medium. These correlations originate from scattering events which take place close to a point source. The scattered waves propagate by diffusion to distant regions. In this way long range correlations, between any pair of distant points, are established.