Scheme for generating entangled states of two field modes in a cavity

The intention of this work is twofold: first, to present a most simple system capable of simulating the intrinsic bosonic Josephson effect with photons and, second, to study various outcomes deriving from inherent or external decoherence. A qubit induces an effective coupling between two externally pumped cavity modes. Without cavity losses and in the dispersive regime, intrinsic Josephson oscillations of photons between the two modes occurs. In this case, contrary to regular Markovian decoherence, the qubit purity shows a Gaussian decay and recurrence of its coherence. Due to intrinsic nonlinearities, both the Josephson oscillations as well as the qubit properties display a rich collapse-revival structure, where, however, the complexity of the qubit evolution is in some sense stronger. The qubit as a meter of the photon dynamics is considered, and it is shown that qubit dephasing, originating, for example, from nondemolition measurements, results in an exponential destruction of the oscillations which manifests the collectiveness of the Josephson effect. Nonselective qubit measurements, on the other hand, render a Zeno effect seen in a slowing down of the Josephson oscillations. Contrary to dephasing, cavity dissipation results in a Gaussian decay of the scaled Josephson oscillations. Finally, following Ponomarev et al. [Phys. Rev. Lett. 106, 010405 (2011)], we analyze aspects of thermalization. In particular, despite similarities with the generic model studied by Ponomarev et al., our system does not seem to thermalize.052103-2 ANOMALOUS DECOHERENCE AND ABSENCE OF . . . PHYSICAL REVIEW A 83, 052103 (2011)

“…In the large detuning regime, g Â †Â , we impose an adiabatic approximation [33] to find, up to some trivial constants,…”

Section: Intrinsic Photonic Josephson Effect In a Bimodal Resonatormentioning

confidence: 99%

Anomalous decoherence and absence of thermalization in a photonic many-body system

Larson

2011

“…033606-2 being coherent with an amplitude determined by the balancing of losses κ and pumping η. The cavity is taken to couple dispersively to the atoms, and the excited atomic state can hence be eliminated adiabatically [22]. In a frame rotating with the pump frequency ω p and assuming ultracold atoms, the Hamiltonian reads [15] …”

Section: A Cavity-mediated Double-well For Cold Atomsmentioning

confidence: 99%

Ultracold atoms in a cavity-mediated double-well system

Larson

Martikainen

2010

We study ground-state properties and dynamics of a dilute ultracold atomic gas in a double-well potential. The Gaussian barrier separating the two wells derives from the interaction between the atoms and a quantized field of a driven Fabry-Perot cavity. Due to intrinsic atom-field nonlinearity, several interesting phenomena arise which are the focus of this work. For the ground state, there is a critical pumping amplitude in which the atoms self-organize and the intra-cavity-field amplitude drastically increases. In the dynamical analysis, we show that the Josephson oscillations depend strongly on the atomic density and may be greatly suppressed within certain regimes, reminiscent of self-trapping of Bose-Einstein condensates in double-well setups. This pseudo-self-trapping effect is studied within a mean-field treatment valid for large atom numbers. For small numbers of atoms, we consider the analogous many-body problem and demonstrate a collapse-revival structure in the Josephson oscillations.

“…[12,13], as well. Recently, many researchers have been regarded the JCM as a source of the entanglement [14,15,16,17,18,19,20,21,22,23].…”

Section: Entanglement Between the Atom And The Thermal Fieldmentioning

confidence: 99%

“…In Ref. [16], an atom interacting with two cavity modes is considered and it is shown that this system can be reduced to the JCM. Using this system, generation of entangled coherent states is discussed.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the Bloch vector in the thermal Jaynes-Cummings model

Azuma¹

2008

In this paper, we investigate the dynamics of the Bloch vector of a single two-level atom which interacts with a single quantized electromagnetic field mode according to the Jaynes-Cummings model, where the field is initially prepared in a thermal state. The time evolution of the Bloch vector S(t) seems to be in complete disorder because of the thermal distribution of the initial state of the field. Both the norm and the direction of S(t) oscillate hard and their periods seem infinite. We observe that the trajectory of the time evolution of S(t) in the two-or three-dimensional space does not form a closed path. To remove the fast frequency oscillation from the trajectory, we take the time-average of the Bloch vector S(t). We examine the histogram of {Sz(n∆t)|n = 0, 1, ..., N } for small ∆t and large N . It represents an absolute value of a derivative of the inverse function of Sz(t). (When the inverse function of y = Sz(t) is a multi-valued function, the histogram represents a summation of the absolute values of its derivatives at points whose real parts are equal to y on the Riemann surface.) We examine the dependence of the variance of the histogram on the temperature of the field. We estimate the lower bound of the entanglement between the atom and the field.