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Experimental on-demand recovery of entanglement by local operations within non-Markovian dynamics.

Orieux A, D'Arrigo A, Ferranti G, Lo Franco R, Benenti G, Paladino E, Falci G, Sciarrino F, Mataloni P - Sci Rep (2015)

Bottom Line: Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand.The restored entanglement is a manifestation of "hidden" quantum correlations resumed by the local control.Relying on local control, both schemes improve the efficiency of entanglement sharing in distributed quantum networks.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro, 5, I-00185 Roma, Italy.

ABSTRACT
In many applications entanglement must be distributed through noisy communication channels that unavoidably degrade it. Entanglement cannot be generated by local operations and classical communication (LOCC), implying that once it has been distributed it is not possible to recreate it by LOCC. Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand. First, we implement an open-loop control scheme based on a purely local operation, without acquiring any information on the environment; then, we use a closed-loop scheme in which the environment is measured, the outcome controling the local operations on the system. The restored entanglement is a manifestation of "hidden" quantum correlations resumed by the local control. Relying on local control, both schemes improve the efficiency of entanglement sharing in distributed quantum networks.

No MeSH data available.


Open-loop results.Entanglement of formation Ef measured at each step k for three values of μ ((a) μ = 1.0. (b) μ = 0.7. (c) μ = 0.2). Symbols: experimental data points, continuous line: theoretical calculations for a Bell state, dotted lines: simulations for a state with a fidelity F = 0.96 to a Bell state. Black, blue and red colours correspond respectively to the uncontrolled, corrected and echoed dynamics. The error bars are derived from propagating the Poissonian statistical errors of the photon coincidence counting.
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f2: Open-loop results.Entanglement of formation Ef measured at each step k for three values of μ ((a) μ = 1.0. (b) μ = 0.7. (c) μ = 0.2). Symbols: experimental data points, continuous line: theoretical calculations for a Bell state, dotted lines: simulations for a state with a fidelity F = 0.96 to a Bell state. Black, blue and red colours correspond respectively to the uncontrolled, corrected and echoed dynamics. The error bars are derived from propagating the Poissonian statistical errors of the photon coincidence counting.

Mentions: The reduced dynamics of AB induced by noise is in this case unambiguously described by the quantum ensemble , where stands for the joint probability p(χ1, χ2, χ3, χ4) andwith the overall phase accumulated up to step k. As a result, each state of the ensemble is maximally entangled, so that also the average entanglement (2) is maximum for any k: . However, the entanglement (1) of the average state, Eρ(k), exhibits quite a different behavior. The system concurrence for the uncontrolled dynamics decays with k: in the case μ = 1 (full correlations), theory gives . For μ < 1 the concurrence, though more involved (see Methods), shows a similarly decaying behavior. In the experiment we measured the entanglement Eρ(k) obtained for three different values of μ with the generated sets of random phase sequences . For k < 4, the LCi with i > k are set at a constant phase instead of χi. The experimental (black symbols) and theoretical results (black lines) are presented in Fig. 2. These results show that the system entanglement decreases as the accumulated phase φk grows.


Experimental on-demand recovery of entanglement by local operations within non-Markovian dynamics.

Orieux A, D'Arrigo A, Ferranti G, Lo Franco R, Benenti G, Paladino E, Falci G, Sciarrino F, Mataloni P - Sci Rep (2015)

Open-loop results.Entanglement of formation Ef measured at each step k for three values of μ ((a) μ = 1.0. (b) μ = 0.7. (c) μ = 0.2). Symbols: experimental data points, continuous line: theoretical calculations for a Bell state, dotted lines: simulations for a state with a fidelity F = 0.96 to a Bell state. Black, blue and red colours correspond respectively to the uncontrolled, corrected and echoed dynamics. The error bars are derived from propagating the Poissonian statistical errors of the photon coincidence counting.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4339803&req=5

f2: Open-loop results.Entanglement of formation Ef measured at each step k for three values of μ ((a) μ = 1.0. (b) μ = 0.7. (c) μ = 0.2). Symbols: experimental data points, continuous line: theoretical calculations for a Bell state, dotted lines: simulations for a state with a fidelity F = 0.96 to a Bell state. Black, blue and red colours correspond respectively to the uncontrolled, corrected and echoed dynamics. The error bars are derived from propagating the Poissonian statistical errors of the photon coincidence counting.
Mentions: The reduced dynamics of AB induced by noise is in this case unambiguously described by the quantum ensemble , where stands for the joint probability p(χ1, χ2, χ3, χ4) andwith the overall phase accumulated up to step k. As a result, each state of the ensemble is maximally entangled, so that also the average entanglement (2) is maximum for any k: . However, the entanglement (1) of the average state, Eρ(k), exhibits quite a different behavior. The system concurrence for the uncontrolled dynamics decays with k: in the case μ = 1 (full correlations), theory gives . For μ < 1 the concurrence, though more involved (see Methods), shows a similarly decaying behavior. In the experiment we measured the entanglement Eρ(k) obtained for three different values of μ with the generated sets of random phase sequences . For k < 4, the LCi with i > k are set at a constant phase instead of χi. The experimental (black symbols) and theoretical results (black lines) are presented in Fig. 2. These results show that the system entanglement decreases as the accumulated phase φk grows.

Bottom Line: Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand.The restored entanglement is a manifestation of "hidden" quantum correlations resumed by the local control.Relying on local control, both schemes improve the efficiency of entanglement sharing in distributed quantum networks.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro, 5, I-00185 Roma, Italy.

ABSTRACT
In many applications entanglement must be distributed through noisy communication channels that unavoidably degrade it. Entanglement cannot be generated by local operations and classical communication (LOCC), implying that once it has been distributed it is not possible to recreate it by LOCC. Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand. First, we implement an open-loop control scheme based on a purely local operation, without acquiring any information on the environment; then, we use a closed-loop scheme in which the environment is measured, the outcome controling the local operations on the system. The restored entanglement is a manifestation of "hidden" quantum correlations resumed by the local control. Relying on local control, both schemes improve the efficiency of entanglement sharing in distributed quantum networks.

No MeSH data available.