The preparation and storage of photonic entanglement are central to the achievement of scalable linear optical quantum computation1, 2, 3 (LOQC). The most widely used photonic entanglement source (a spontaneous parametric downconversion (SPDC) source)4, 5 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 sources6, 7, 8, 9, 10, 11, 12 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 LOQC5, 13, 14. 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.
At a glance
- A scheme for efficient quantum computation with linear optics. Nature 409, 46–52 (2001). , &
- Resource-efficient linear optical quantum computation. Phys. Rev. Lett. 95, 010501 (2005). &
- Linear optical quantum computing with photonic qubits. Rev. Mod. Phys. 79, 135–174 (2007). et al.
- New high-intensity source of polarization-entangled photon pairs. Phys. Rev. Lett. 75, 4337–4341 (1995). et al.
- Multi-photon entanglement and interferometry. Rev. Mod. Phys. (submitted); preprint at http://arxiv.org/abs/0805.2853. et al.
- Cavity enhanced spontaneous parametric down-conversion for the prolongation of correlation time between conjugate photons. Phys. Rev. Lett. 83, 2556–2559 (1999). &
- Time-bin-modulated biphotons from cavity enhanced down-conversion. Phys. Rev. Lett. 97, 223601 (2006). et al.
- Bright filter-free source of indistinguishable photon pairs. Opt. Express 16, 18145–18151 (2008). et al.
- Generation of narrow-band polarization-entangled photon pairs for atomic quantum memories. Phys. Rev. Lett. 101, 190501 (2008). et al.
- Statisics of narrow-band single photons for quantum memories generation by ultrabright cavity-enhanced parametric down-conversion. Phys. Rev. Lett. 102, 063603 (2009). et al.
- Experimental quantum teleportation and multiphoton entanglement via interfering narrowband photon sources. Phys. Rev. A 80, 042321 (2009). et al.
- Time gating of heralded single photons for atomic memories. Opt. Lett. 34, 3872–3874 (2009). , &
- Photon bunching and multiphoton interference in parametric down-conversion. Phys. Rev. A 60, 593–604 (1999). et al.
- Effects of spectral entanglement in polarization-entanglement swapping and type-I fusion gates. Phys. Rev. A 77, 022312 (2008). &
- Experimental one-way quantum computing. Nature 434, 169–176 (2005). et al.
- Silica-on-silicon waveguide quantum circuits. Science 320, 646–649 (2008). et al.
- Experimental demonstration of a heralded entanglement source. Nature Photon. 4, 549–552 (2010). et al.
- Heralded generation of entangled photon pairs. Nature Photon. 4, 553–556 (2010). et al.
- Towards high-speed optical memories. Nature Photon. 4, 218–221 (2010). et al.
- Storage and retrieval of nonclassical photon pairs and conditional single photons generated by the parametric down-conversion process. New J. Phys. 11, 013049 (2009). et al.
- Heralded generation of ultrafast single photons in pure quantum states. Phys. Rev. Lett. 100, 133601 (2008). et al.
- Pure-state single-photon wave-packet generation by parametric down-conversion in a distributed microcavity. Phys. Rev. A 72, 023825 (2005). et al.
- Non-classical interference between independent sources. J. Opt. B 7, S171–S175 (2005). et al.
- Dark-State Polaritons in Electromagnetically Induced Transparency. Phys. Rev. Lett. 84, 5094–5097 (2000). and
- Storage of light in atomic vapor. Phys. Rev. Lett. 86, 783–786 (2001). et al.
- Observation of coherent optical information storage in an atomic medium using halted light pulses. Nature 409, 490–493 (2001). et al.
- Storage and retrieval of single photons transmitted between remote quantum memories. Nature 438, 833–836 (2005). et al.
- Electromagnetically induced transparency with tunable single-photon pulses. Nature 438, 837–841 (2005). et al.
- Mapping photonic entanglement into and out of a quantum memory. Nature 452, 67–71 (2008). et al.
- Quantum memory for squeezed light. Phys. Rev. Lett. 100, 093602 (2008). et al.
- High densities of cold atoms in a dark spontaneous-force optical trap. Phys. Rev. Lett. 70, 2253–2256 (1993). et al.
- Single-photon generation from stored excitation in an atomic ensemble. Phys. Rev. Lett. 92, 213601 (2004). et al.
- A millisecond quantum memory for scalable quantum networks. Nature Phys. 5, 95–99 (2009). et al.
- Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett. 23, 880–884 (1969). , , &
- Scalable generation of graph-state entanglement through realistic linear optics. Phys. Rev. Lett. 97, 143601 (2006). &
- Fault-tolerant quantum repeater with atomic ensembles and linear optics. Phys. Rev. A 76, 022329 (2007). et al.
- A one-way quantum computer. Phys. Rev. Lett. 86, 5188–5191 (2001). &
- Heralded generation of an atomic NOON state. Phys. Rev. Lett. 104, 043601 (2010). et al.
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