Cooling atom-cavity systems into entangled states

Abstract

Generating entanglement by simply cooling a system into a stationary state which is highly entangled has many advantages. Schemes based on this idea are robust against parameter fluctuations, tolerate relatively large spontaneous decay rates, and achieve high fidelities independent of their initial state. A possible implementation of this idea in atom-cavity systems has recently been proposed by Kastoryano et al. [Phys. Rev. Lett. 106, 090502 (2011)]. Here we propose an improved entanglement cooling scheme for two atoms inside an optical cavity which achieves higher fidelities for comparable single-atom cooperativity parameters C. For example, we predict fidelities above 90% even for C as low as 20 without requiring individual laser addressing and without having to detect photons.Comment: 12 pages, 11 figure

Stationary three-dimensional entanglement via dissipative Rydberg pumping

“…In Fig. 2, we characterizes the dynamical evolution of negativity N (ρ ∞ ) versus the single-photon detuning parameter ∆ and the spontaneously decay rate γ by numerically solving the steady-state equation (18). It is shown that the negativity keeps high over a wide range of parameters.…”

“…the three-dimensional entangled stateρ ∞ = |Ψ Ψ| is the unique solution of Eq. (18). To effectively measure this kind of three-dimensional entanglement of two particles, we need to introduce the trace norm of the partial transposition ||ρ…”

“…It is worth noting that the proposed mechanism is much more like the cooling mechanism in Refs. [15,18], where the laser sideband cooling is applied to induce a relatively large detuning of the desired state but resonant lasers drive all other qubit states. Therefore, our method can also be reconsidered as a cooling process that the whole system is finally cooled into the three-dimensional entangled state at the coaction of Rydberd interaction and spontaneous emission.…”

“…This work has shed new light on quantum information processing since it illustrates that the dissipation can be utilized as a resource to prepare entanglement and implement universal quantum computing. Since then, the dissipationbased protocols have sprung up in various quantum information tasks [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. For instance, Kastoryano et al prepared a maximally bipartite-entanglement state in a leaking optical cavity [16].…”

Engineering Dissipative Channels for Realizing Schrödinger Cats in SQUIDs

“…Two-photon absorption has also been suggested as a powerful resource for application in quantum computing (Franson et al, 2004). We note that there already exist schemes for realizing non-classical states via engineered dissipative channels (Amico et al, 2008;Diehl et al, 2008;Kraus et al, 2008;Schirmer and Wang, 2010;Ticozzi et al, 2010;Zhang et al, 2010;Busch et al, 2011;Pechen, 2011;Scully et al, 2011;Chen et al, 2012;Ticozzi and Viola, 2012;Yamamoto, 2012;Ikeda and Yamamoto, 2013) as well as a number of experimental realizations (Barreiro et al, 2011;Krauter et al, 2011;Leghtas et al, 2013). We also note that SQUIDs are an ideal candidate system for realizing this protocol as they have already been shown able to support appropriate quantum states (Nakamura et al, 1999;Friedman et al, 2000;Grajcar et al, 2004;Il'Ichev et al, 2004) and, as we shall later show, existing circuit designs can be used to engineer an environment with the suitable characteristics (Deng et al, 2010;Kumar and DiVincenzo, 2010).…”