Thermal Relaxation of a QED Cavity

Mykola Bordyuh, Marco Schirò, Camille Aron +2 more

Daniele De Bernardis

We study the open relaxation dynamics of an asymmetric dipole that is ultrastrongly coupled to a single electromagnetic cavity mode. By using a thermalizing master equation for the whole interacting system we derive a phase diagram of the Liouvillian gap. It emerges that the ultrastrong coupling inhibits the system's relaxation toward the equilibrium state due to an exponential suppression of the dipole tunneling rate. However, we find that polaronic multiphoton resonances restore fast relaxation by a cavity-mediated dipole resonant tunneling process. Aside from the numerical evidence, we develop a fully analytical description by diagonalizing the Rabi model through a generalized rotating-wave approximation, valid in the so-called polaron frame. The relaxation physics of such ultrastrong-coupling systems is then reduced to a multiphoton polaron version of the standard textbook dressed states picture. At the end we discuss an extension to a multiwell dipole that can set the basis of a cascaded resonant tunneling setup in the ultrastrong coupling regime.

T. Zaugg, Georg Lenz, Pierre Meystre

Hayato Goto, Kouichi Ichimura

A condition for fault-tolerant quantum computation (FTQC) with cavity schemes is discussed. It is shown that the condition is very hard if the standard error threshold of FTQC is simply applied. To relax the condition, we propose to combine the cavity-quantum-electrodynamics (QED) scheme proposed by Duan et al. [Phys. Rev. A 72, 032333 (2005)] and Xiao et al. [Phys. Rev. A 70, 042314 (2004)] with the recently proposed FTQC scheme with probabilistic two-qubit gates [Goto and Ichimura, Phys. Rev. A 80, 040303(R) (2009)]. It is shown that the condition for FTQC is dramatically relaxed compared to the case of the standard threshold. The optimization of the cavity-QED scheme is also discussed.

Dong Ping, Song Wei, Zhuo‐Liang Cao

We propose a simple scheme for implementing Deutsch–Jozsa algorithm in cavity QED. Our scheme is insensitive to both the cavity decay and thermal field because we use the large-detuned interaction. The scheme would be important to constructing practical computer in cavity QED system.