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November 17, 2012

Quantum teleportation between remote atomic-ensemble quantum memories

Arxiv - Quantum teleportation and quantum memory are two crucial elements for large-scale quantum networks. With the help of prior distributed entanglement as a "quantum channel", quantum teleportation provides an intriguing means to faithfully transfer quantum states among distant locations without actual transmission of the physical carriers. Quantum memory enables controlled storage and retrieval of fast flying photonic quantum bits with stationary matter systems, which is essential to achieve the scalability required for large-scale quantum networks. Combining these two capabilities, here we realize quantum teleportation between two remote atomic-ensemble quantum memory nodes, each composed of 10^8 rubidium atoms and connected by a 150-meter optical fiber. The spinwave state of one atomic ensemble is mapped to a propagating photon, and subjected to Bell-state measurements with another single photon that is entangled with the spinwave state of the other ensemble. Two-photon detection events herald the success of teleportation with an average fidelity of 88(7)%. Besides its fundamental interest as the first teleportation between two remote macroscopic objects, our technique may be useful for quantum information transfer between diff erent nodes in quantum networks and distributed quantum computing



Methods for further increasing the success probability include using a low- nesse optical cavity to improve the spinwave-to-photon conversion e fficiency (higher A), and using the measurement-based scheme and another assisted ensemble to create the auxiliary photon-spinwave entanglement near deterministically (higher PB). In the present experiment, the storage lifetime ( 129 s) of the prepared spinwave states in the quantum memories slightly exceeds the average time required ( 97.5 s) to create a pair of assistant remote entanglement for teleportation. The storage lifetime in the atomic ensembles can be increased up to 100 ms by making use of optical lattices to con nect atomic motion. With these improvements we could envision quantum teleportation experiments among multiple atomic-ensemble nodes in the future.




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