Efficient entanglement distillation without quantum memory

Abstract

Entanglement distribution between distant parties is an essential component to most quantum communication protocols. Unfortunately, decoherence effects such as phase noise in optical fibers are known to demolish entanglement. Iterative (multistep) entanglement distillation protocols have long been proposed to overcome decoherence, but their probabilistic nature makes them inefficient since the success probability decays exponentially with the number of steps. Quantum memories have been contemplated to make entanglement distillation practical, but suitable quantum memories are not realised to date. Here, we present the theory for an efficient iterative entanglement distillation protocol without quantum memories and provide a proof-of-principle experimental demonstration. The scheme is applied to phase-diffused two-mode-squeezed states and proven to distill entanglement for up to three iteration steps. The data are indistinguishable from those an efficient scheme using quantum memories would produce. Since our protocol includes the final measurement it is particularly promising for enhancing continuous-variable quantum key distribution.

8 pages, 5 figures

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• Enhancement of nonclassical properties of two-mode squeezed vacuum state with postselected von Neumann measurement
• Experimental quantum decoherence control by dark states of the environment
• Quantum Communication Networks Enhanced by Distributed Quantum Memories
• Entanglement Enhancement in Multimode Integrated Circuits
• Experimental investigation of heralded Gaussification of phase-randomized coherent states of light
• Entanglement distillation in terms of a conjectured matrix inequality
• On-chip squeezed light in the audio frequency band