Optimized generation of entanglement based on the f-STIRAP technique

We consider generating maximally entangled states(Bell states)between two qubits coupled to a common bosonic mode,based on f-STIRAP.Utilizing the systematic approach developed by Wang et al(2017 New J.Phys.19093016),we quantify the effects of non-adiabatic leakage and system dissipation on the entanglement generation,and optimize the entanglement by balancing non-adiabatic leakage and system dissipation.We find the analytical expressions of the optimal coupling profile,the operation time,and the maximal entanglement.Our findings have broad applications in quantum state engineering,especially in solid-state devices where dissipative effects cannot be neglected.

Quantum dynamics of Gaudin magnets

Quantum dynamics of many-body systems is a fascinating and significant subject for both theory and experiment.The question of how an isolated many-body system evolves to its steady state after a sudden perturbation or quench still remains challenging.In this paper,using the Bethe ansatz wave function,we study the quantum dynamics of an inhomogeneous Gaudin magnet.We derive explicit analytical expressions for various local dynamic quantities with an arbitrary number of flipped bath spins,such as:the spin distribution function,the spin-spin correlation function,and the Loschmidt echo.We also numerically study the relaxation behavior of these dynamic properties,gaining considerable insight into coherence and entanglement between the central spin and the bath.In particular,we find that the spin-spin correlations relax to their steady value via a nearly logarithmic scaling,whereas the Loschmidt echo shows an exponential relaxation to its steady value.Our results advance the understanding of relaxation dynamics and quantum correlations of long-range interacting models of the Gaudin type.

Enhancing photon entanglement in a three-mode optomechanical system via imperfect phonon measurements

By considering a 3-mode optomechanical system formed by two cavities interacting with a common mechanical mode,we demonstrate that phonon-counting measurements lead to a significant enhancement of entanglement in the output of the two cavities.This conclusion still holds for an inefficient detector,but the dependence on system parameters changes qualitatively from the ideal limit of perfect projective measurements.We find non-trivial optimal points for the entanglement as functions of detector efficiency,measurement outcome,and optical drive strengths.We characterize both the highest achievable entanglement as well as a‘typical’value,obtained at the most likely measurement outcome.Numerical results are well understood within an approximate analytical approach based on perturbation theory around the ideal detector limit.

Reservoir-engineered entanglement in an unresolved-sideband optomechanical system

We study theoretically the generation of strong entanglement of two mechanical oscillators in an unresolved-sideband optomechanical cavity,using a reservoir engineering approach.In our proposal,the effect of unwanted counter-rotating terms is suppressed via destructive quantum interference by the optical field of two auxiliary cavities.For arbitrary values of the optomechanical interaction,the entanglement is obtained numerically.In the weak-coupling regime,we derive an analytical expression for the entanglement of the two mechanical oscillators based on an effective master equation,and obtain the optimal parameters to achieve strong entanglement.Our analytical results are in accord with numerical simulations.