Quantum entanglement maintained by virtual excitations in an ultrastrongly-coupled-oscillator system

Abstract

We study the effect of quantum entanglement maintained by virtual excitations in an ultrastronglycoupled harmonic-oscillator system. Here, the quantum entanglement is caused by the counterrotating interaction terms and hence it is maintained by the virtual excitations. We obtain the analytical expression for the ground state of the system and analyze the relationship between the average excitation numbers and the ground-state entanglement. We also study the entanglement dynamics between the two oscillators in both the closed-and open-system cases. In the latter case, the quantum master equation is microscopically derived in the normal-mode representation of the coupled-oscillator system. This work will open a route to the study of quantum information processing and quantum physics based on virtual excitations.

Optical Amplification and Fast-Slow Light in a Three-Mode Cavity Optomechanical System without Rotating Wave Approximation

“…However, these previous works ignore the influence of the rotating wave approximation (RWA) method on the system. As is well-known, the counterrotating term is an important term in the dynamic analysis of system, which has a great influence on the system [66][67][68]. For example, the quantum entanglement caused by the counterrotating term has been found for an ultrastrongly coupled oscillator system in Ref.…”

“…For example, the quantum entanglement caused by the counterrotating term has been found for an ultrastrongly coupled oscillator system in Ref. [66]. The ideal OMIT effect has been achieved using the counterrotating term for the cononical optomechanical model in Ref.…”

Dynamical Invariant and Exact Mechanical Analyses for the Caldirola–Kanai Model of Dissipative Three Coupled Oscillators

“…Description and interpretation of coupled systems are of particular interest in physics because the interaction caused by coupling is responsible for novel quantum effects such as entanglement [ 1 , 2 ] and quadrature squeezing [ 3 ]. Coupled oscillatory quantum motions are found in almost all areas of physical sciences, ranging from nanotechnology to biology [ 4 , 5 , 6 , 7 , 8 ].…”

Instability of Meissner Differential Equation and Its Relation with Photon Excitations and Entanglement in a System of Coupled Quantum Oscillators

“…The connection between normal mode instability and entanglement growth was also demonstrated in References [16,17], again by using sinusoidal coupling. More recently, it was shown in Reference [18] that the ground state |G of two time-independent resonant oscillators contains, in the USC regime, virtual (cannot be absorbed) excitations VE, i.e., G|N 1 |G = G|N 2 |G = 0, with N 1 and N 2 being the photon number operators corresponding to the coupled oscillators. Note that the term VE is used here to denote virtual photons that exist in the ground state but cannot be detected directly [18], although there are some proposals in order to probe them [19,20].…”

“…More recently, it was shown in Reference [18] that the ground state |G of two time-independent resonant oscillators contains, in the USC regime, virtual (cannot be absorbed) excitations VE, i.e., G|N 1 |G = G|N 2 |G = 0, with N 1 and N 2 being the photon number operators corresponding to the coupled oscillators. Note that the term VE is used here to denote virtual photons that exist in the ground state but cannot be detected directly [18], although there are some proposals in order to probe them [19,20]. This is not to be confused with the usage of the term in several other works [21][22][23][24][25] in which qubits detuned from a cavity where they are embedded and interact through the virtual exchange of photons with the cavity.…”