Preparation of optimal entropy squeezing state of atomic qubit inside the cavity via two-photon process and manipulation of atomic qubit outside the cavity

Abstract

Considering two atomic qubits initially in Bell states, we send one qubit into a vacuum cavity with two-photon resonance and leave the other one outside. Using quantum information entropy squeezing theory, the time evolutions of the entropy squeezing factor of the atomic qubit inside the cavity are discussed for two cases, i.e., before and after rotation and measurement of the atomic qubit outside the cavity. It is shown that the atomic qubit inside the cavity has no entropy squeezing phenomenon and is always in a decoherent state before the operating atomic qubit outside the cavity. However, the periodical entropy squeezing phenomenon emerges and the optimal entropy squeezing state can be prepared for the atomic qubit inside the cavity by adjusting the rotation angle, choosing the interaction time between the atomic qubit and the cavity, controlling the probability amplitudes of subsystem states. Its physical essence is cutting the entanglement between the atomic qubit and its environment, causing the atomic qubit inside the cavity to change from the initial decoherent state into maximum coherent superposition state, which is a possible way of recovering the coherence of a single atomic qubit in the noise environment.

Generation of sustained optimal entropy squeezing of a two-level atom via non-Hermitian operation

“…Furthermore, an optimal squeezing state corresponds to a quantum state with minimum quantum noise, and sustained squeezing can provide long enough time for scientists to make use of the squeezing resource to perform quantum information processing, quantum computation, and quantum communication. According to most of previous works, [2][3][4] available squeezing effects at most possess either optimal squeezing degree or long squeezing time, but not both. As far as we know, it is difficult to prepare the squeezing resource which possesses not only optimal squeezing degree but also long persistence time.…”

On the nonclassical dynamics of cavity-assisted four-channel nonlinear coupler

“…Rapid technological advancements in recent years allow strong squeezing to be generated in a number of nonlinear processes and quantum systems, e.g., parametric oscillators, [9][10][11][12] second harmonic generation, [13] atom-cavity couplings, [14][15][16] semiconductor microcavities, [17][18][19] optomechanical, [20][21][22] and nonlinear directional couplers (NLDC). [23][24][25][26] Systems having inherent fast nonlinear response, such as Kerr NLDC, however, possess the potential in generating strong squeezed light, especially when placed inside a cavity to resonantly amplify the nonlinearity.…”