115 research outputs found
"Hot Entanglement"? -- A Nonequilibrium Quantum Field Theory Scrutiny
The possibility of maintaining entanglement in a quantum system at finite,
even high, temperatures -- the so-called `hot entanglement' -- has obvious
practical interest, but also requires closer theoretical scrutiny. Since
quantum entanglement in a system evolves in time and is continuously subjected
to environmental degradation, a nonequilibrium description by way of open
quantum systems is called for. To identify the key issues and the contributing
factors that may permit `hot entanglement' to exist, or the lack thereof, we
carry out a model study of two spatially-separated, coupled oscillators in a
shared bath depicted by a finite-temperature scalar field. From the Langevin
equations we derived for the normal modes and the entanglement measure
constructed from the covariance matrix we examine the interplay between direct
coupling, field-induced interaction and finite separation on the structure of
late-time entanglement. We show that the coupling between oscillators plays a
crucial role in sustaining entanglement at intermediate temperatures and over
finite separations. In contrast, the field-induced interaction between the
oscillators which is a non-Markovian effect, becomes very ineffective at high
temperature. We determine the critical temperature above which entanglement
disappears to be bounded in the leading order by the inverse frequency of the
center-of-mass mode of the reduced oscillator system, a result not unexpected,
which rules out hot entanglement in such settings.Comment: 13 pages, 2 figure
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