Non-Markovian thermal reservoirs for autonomous entanglement distribution

Abstract

We describe a novel scheme for the generation of stationary entanglement between two separated qubits that are driven by a purely thermal photon source. While in this scenario the qubits remain in a separable state at all times when the source is broadband, i.e. Markovian, the qubits relax into an entangled steady state once the bandwidth of the thermal source is sufficiently reduced. We explain this phenomenon by the appearance of a quasiadiabatic dark state and identify the most relevant nonadiabatic corrections that eventually lead to a breakdown of the entangled state, once the temperature is too high. This effect demonstrates how the non-Markovianity of an otherwise incoherent reservoir can be harnessed for quantum communication applications in optical, microwave, and phononic networks. As two specific examples, we discuss the use of filtered room-temperature noise as a passive resource for entangling distant superconducting qubits in a cryogenic quantum link or solid-state spin qubits in a phononic quantum channel.