Abstract

We study entanglement and squeezing of two uncoupled impurities immersed in a Bose-Einstein condensate. We treat them as two quantum Brownian particles interacting with a bath composed of the Bogoliubov modes of the condensate. The Langevin-like quantum stochastic equations derived exhibit memory effects. We study two scenarios: (i) In the absence of an external potential, we observe sudden death of entanglement; (ii) In the presence of an external harmonic potential, entanglement survives even at the asymptotic time limit. Our study considers experimentally tunable parameters.

Highlights

  • The Bose polaron problem was recently studied within the quantum Brownian motion (QBM) model [43, 48], which describes the dynamics of a quantum particle interacting with a bath made up of a huge number of harmonic oscillators obeying the Bose-Einstein statistics [6,49,50,51]

  • From here on we treat only the one dimensional case, i.e. we assume that the Bose-Einstein condensate (BEC) and the impurities are so tightly trapped in two directions as to effectively freeze the dynamics in those directions

  • We studied the emergent entanglement between two distinguishable polarons due to their common coupling to a BEC bath

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Summary

Introduction

Entanglement represents a necessary resource for a number of protocols in quantum information and for other quantum technologies, which are expected to be implemented in the foreseeable future for various practical applications [1,2,3,4,5]. The Bose polaron problem was recently studied within the quantum Brownian motion (QBM) model [43, 48], which describes the dynamics of a quantum particle interacting with a bath made up of a huge number of harmonic oscillators obeying the Bose-Einstein statistics [6,49,50,51] In this analogy, the impurity plays the role of the Brownian particle and the Bogoliubov excitations of the BEC are the bath-oscillators. This set of two coupled equations are non-local in time, namely the dynamics of both impurities in a BEC carry certain amount of memory In this context, such a feature is often related to the super-Ohmic character of the spectral density, constituting the main quantity that embodies the properties of the bath. D we study, for the trapped case, the effective equilibrium Hamiltonian of the system reached at long-times

Hamiltonian
Heisenberg equations
Spectral density
Solution of Heisenberg equations and covariance matrix
Entanglement measure
Squeezing
Results
Out-of-equilibrium dynamics and entanglement of the untrapped impurities
Squeezing and Entanglement for Trapped impurities
Thermal entanglement induced by isotropic substrates
Conclusions
A Spectral density
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