Enhancement of spontaneous entanglement generation via coherent quantum feedback

Abstract

We investigate the entanglement dynamics of two two-level emitters (qubits) mediated by a semiinfinite, one-dimensional (1D) photonic waveguide. The coupling of each qubit to the waveguide is chiral, which depends on the propagation direction of light. The finite end of the waveguide is terminated by a perfect mirror, such that coherent quantum feedback is introduced to the system. We show that the chirally generated entanglement between the qubits can be preserved by controlling the time delay of the feedback. Moreover, when the time delay is negligible, the qubit-qubit reduced system evolves within the strong-coupling regime and the qubits can be almost maximally entangled. We also analyze the robustness of the protocol against variations of some relevant parameters.

Quantum trajectory theory of few-photon cavity-QED systems with a time-delayed coherent feedback

“…When the waveguide is included in the Hamiltonian, the Hilbert space can quickly become very large and so specialized methods are used to model its evolution. When limited to the linear regime, results can be computed analytically but this significantly restricts the phenomena that can be investigated [1,3,59,60]. A popular method for modelling coherent feedback is matrix product states (MPSs) [21,26,34,52,[61][62][63][64], a powerful technique where tensor networks are used to limit the entanglement within the Hilbert space.…”

Does anti-Unruh effect assist quantum entanglement and coherence?

“…It is a necessary ingredient for various computational tasks, such as quantum remote control, quantum teleportation and quantum communication [1][2][3]. A lot of progresses have been made in understanding the behavior of quantum entanglement in various aspects, such as the sudden death and sudden birth, the degeneration or enhancement of quantum entanglement [4][5][6][7][8][9][10]. On the other hand, as a broader concept, quantum coherence is also a physical resource in quantum technologies, optical experiments and biological systems [11][12][13][14][15].…”