View all news

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

Conceptual scheme.

Conceptual scheme. Qubits A and B are prepared in the Bell state |Ψ−〉. Qubit B interacts stroboscopically with the environment through the 4 random phases x(tk). The noise induced by the environment can be compensated either with a rephasing unitary Ucorr or with an echo-pulse unitary Uecho = σx. Ef: entanglement of formation measurement. (b) Experimental implementation. LC: liquid cristal retarder, HWP: half-wave plate, QWP: quarter-wave plate, PBS: polarizing beam-splitter, SPAD: single photon avalanche photodiode, C: coincidence counting electronics.

2 March 2015

PhD student, Giacomo Ferranti, has had his Masters thesis published as a Scientific Report on

His work, which was undertaken with his previous colleagues at Sapienza University of Rome discusses how 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.

Read the whole article here.

Edit this page