Generation of Narrow-Band Polarization-Entangled Photon Pairs for Atomic Quantum Memories (original) (raw)
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Nature Photonics, 2011
The preparation and storage of photonic entanglement are central to the achievement of scalable linear optical quantum computation (LOQC). The most widely used photonic entanglement source (a spontaneous parametric downconversion (SPDC) source) is not directly suitable for storage, because its working frequency bandwidth is significantly larger than any available quantum memory. To remedy this problem, cavity-enhanced narrow-band SPDC sources have been developed. However, the storage of cavity-enhanced narrow-band entangled photons has not yet been achieved. Also, the spectral correlations between the entangled photons can make them practically useless for scalable LOQC. Here, we report the preparation and storage of frequency-uncorrelated narrowband (5 MHz) entangled photons from a cavity-enhanced SPDC source. The frequency correlation between the entangled photons is eliminated by changing the continuous UV pumping beam to short pulses. The storage of the polarization state of a single photon, and of a photon entangled with another flying in the fibre, is demonstrated. Our work demonstrates a quantum interface between narrow-band entangled photons from cavity SPDC and atomic quantum memory, and thus provides an important tool towards the achievement of all-optical quantum information processing.
Two-mode single-atom laser as a source of entangled light
Physical Review A, 2007
A two-mode single-atom laser is considered, with the aim of generating entanglement in macroscopic light. Two transitions in the four-level gain medium atom independently interact with the two cavity modes, while two other transitions are driven by control laser fields. Atomic relaxation as well as cavity losses are taken into account. We show that this system is a source of macroscopic entangled light over a wide range of control parameters and initial states of the cavity field.