Quantumness and memory of one qubit in a dissipative cavity under classical control

Abstract

Hybrid quantum-classical systems constitute a promising architecture for useful control strategies of quantum systems by means of a classical device. Here we provide a comprehensive study of the dynamics of various manifestations of quantumness with memory effects, identified by non-Markovianity, for a qubit controlled by a classical field and embedded in a leaky cavity. We consider both Leggett-Garg inequality and quantum witness as experimentally-friendly indicators of quantumness, also studying the geometric phase of the evolved (noisy) quantum state. We show that, under resonant qubit-classical field interaction, a stronger coupling to the classical control leads to enhancement of quantumness despite a disappearance of non-Markovianity. Differently, increasing the qubit-field detuning (out-of-resonance) reduces the nonclassical behavior of the qubit while recovering non-Markovian features. We then find that the qubit geometric phase can be remarkably preserved irrespective of the cavity spectral width via strong coupling to the classical field. The controllable interaction with the classical field inhibits the effective time-dependent decay rate of the open qubit. These results supply practical insights towards a classical harnessing of quantum properties in a quantum information scenario.

Enhancement of quantum correlations and geometric phase for a driven bipartite quantum system in a structured environment

“…Quantum decoherence implies a rapid reduction of the off-diagonal terms of the bipartite reduced density matrix. The quantity for measuring the entanglement between the different parts of the composite system is the Concurrence [2,6]. The Concurrence for the evolution of this state can be computed as…”

“…Many different approaches have studied the entanglement properties of bipartite systems in different frameworks. In [6], authors have studied quantum correlations in a two-qubit system coupled to either a common bath or two different baths, focusing on environmental memory effects induced on the bipartite system. In [7], it has been proposed the used of the Quantum Zeno effect to protect the degradation of the entanglement for two atoms in a lossy resonator.…”

Dephasing Process of a Single Atom Interacting with a Two-Mode Field

“…In this way, the control and manipulation of the decoherence can be exploited to enhance the entanglement between the system and its environment. It is proven that the entanglement of the induced steady state between a two-level atom and its spontaneous emission excitation is manipulated by detuning the intensity and relative phase of the fields [ 49 , 50 , 51 , 52 , 53 , 54 ]. It is worth noting that the hybrid entanglement between a photon and an atom has applications in quantum tools, such as quantum networks [ 55 ], quantum repeater [ 56 , 57 ], and so on.…”

The effect of classical driving field on the spectrum of a qubit and entanglement swapping inside dissipative cavities

“…It was shown that the entanglement between two such qubits, which are embedded in two independent cavities, can be preserved for a long time [52]. Moreover, non-Markovianity [53][54][55], quantum Fisher information [56,57], quantum speedup [54], coherence dynamics [58] and quantumness [55] of such a model have been studied.…”