760 research outputs found
Quantum Storage of Photonic Entanglement in a Crystal
Entanglement is the fundamental characteristic of quantum physics. Large
experimental efforts are devoted to harness entanglement between various
physical systems. In particular, entanglement between light and material
systems is interesting due to their prospective roles as "flying" and
stationary qubits in future quantum information technologies, such as quantum
repeaters and quantum networks. Here we report the first demonstration of
entanglement between a photon at telecommunication wavelength and a single
collective atomic excitation stored in a crystal. One photon from an
energy-time entangled pair is mapped onto a crystal and then released into a
well-defined spatial mode after a predetermined storage time. The other photon
is at telecommunication wavelength and is sent directly through a 50 m fiber
link to an analyzer. Successful transfer of entanglement to the crystal and
back is proven by a violation of the Clauser-Horne-Shimony-Holt (CHSH)
inequality by almost three standard deviations (S=2.64+/-0.23). These results
represent an important step towards quantum communication technologies based on
solid-state devices. In particular, our resources pave the way for building
efficient multiplexed quantum repeaters for long-distance quantum networks.Comment: 5 pages, 3 figures + supplementary information; fixed typo in ref.
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A high-speed multi-protocol quantum key distribution transmitter based on a dual-drive modulator
We propose a novel source based on a dual-drive modulator that is adaptable
and allows Alice to choose between various practical quantum key distribution
(QKD) protocols depending on what receiver she is communicating with.
Experimental results show that the proposed transmitter is suitable for
implementation of the Bennett and Brassard 1984 (BB84), coherent one-way (COW)
and differential phase shift (DPS) protocols with stable and low quantum bit
error rate. This could become a useful component in network QKD, where
multi-protocol capability is highly desirable.Comment: 15 pages, 7 figure
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