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arXiv:0907.1831 · Physical Review A

Qubit-mediated time-robust entangling of oscillators in thermal environments

Tommaso Tufarelli, M. S. Kim, Sougato Bose

Published Dec 8, 2009• 4 citations
arXivHTMLPDF

Abstract

We consider two separated oscillators initially in equilibrium and continuously interacting with thermal environments and propose a way to entangle them using a mediating qubit. An appropriate interaction allows for an analytic treatment of the open system, removes the necessity of fine-tuning interaction times, and results in a high tolerance of the entanglement to finite temperature. The entanglement thus produced between the oscillators can be verified either through a Bell inequality relying on oscillator parity measurements or through conditional extraction of the entanglement on two mutually noninteracting qubits. The latter process also shows that the generated mixed-entangled state of the oscillators is an useful resource for entangling qubits. By allowing for influences from environments, taking feasible qubit-oscillator interactions and measurement settings, this scheme should be implementable in a variety of experimental setups. The method presented for the solution of the master equation can also be adapted to a variety of problems involving the same form of qubit-oscillator interaction

DOI
10.1103/physreva.80.062317

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We discuss the deterministic Gaussian entangling procedure between continuous variables of two directly noninteracting oscillators. The oscillators can only couple to the same mediating oscillator, which is initially at arbitrary noisy state and can be lost after the procedure. Unitary idealization of the procedure can generate large entanglement for any initial thermal noise of the mediator, thanks to the quantum version of the geometric phase. The generation of entanglement may considerably change when the procedure contains a weak dissipation. A robustness of this entangling procedure for weak dissipation is therefore a basic test of feasibility, especially in the limit of noisy mediator. We theoretically confirm the basic robustness of entanglement generation. Moreover, we suggest a nontrivial numerical optimization of the entangling procedure to approach an absolute robustness. For the weak dissipation, the optimization allows complete avoiding of the impact of the mediator noise. The suggested entangling procedure is therefore verified to be sufficiently robust for further development of quantum transducers.