Tunable delay of Einstein–Podolsky–Rosen entanglement

Entangled systems display correlations that are stronger than can be obtained classically. This makes entanglement an essential resource for a number of applications, such as quantum information processing, quantum computing and quantum communications. The ability to control the transfer of entanglement between different locations will play a key role in these quantum protocols and enable quantum networks. Such a transfer requires a system that can delay quantum correlations without significant degradation, effectively acting as a short-term quantum memory. An important benchmark for such systems is the ability to delay Einstein–Podolsky–Rosen (EPR) levels of entanglement and to be able to tune the delay. EPR entanglement is the basis for a number of quantum protocols, allowing the remote inference of the properties of one system (to better than its standard quantum limit) through measurements on the other correlated system. Here we show that a four-wave mixing process based on a double-lambda scheme in hot 85Rb vapour allows us to obtain an optically tunable delay for EPR entangled beams of light. A significant maximum delay, of the order of the width of the cross-correlation function, is achieved. The four-wave mixing also preserves the quantum spatial correlations of the entangled beams. We take advantage of this property to delay entangled images, making this the first step towards a quantum memory for images.

[1]  H. J. Kimble,et al.  The quantum internet , 2008, Nature.

[2]  Ou,et al.  Realization of the Einstein-Podolsky-Rosen paradox for continuous variables. , 1992, Physical review letters.

[3]  John C Howell,et al.  Storage and retrieval of multimode transverse images in hot atomic Rubidium vapor. , 2008, Physical review letters.

[4]  B C Buchler,et al.  Delay of squeezing and entanglement using electromagnetically induced transparency in a vapour cell. , 2008, Optics express.

[5]  N Davidson,et al.  Storing images in warm atomic vapor. , 2007, Physical review letters.

[6]  Klaus Mølmer,et al.  Holographic quantum computing. , 2008, Physical review letters.

[7]  Cirac,et al.  Inseparability criterion for continuous variable systems , 1999, Physical review letters.

[8]  D. Akamatsu,et al.  Ultraslow propagation of squeezed vacuum pulses with electromagnetically induced transparency. , 2006, Physical review letters.

[9]  A M Marino,et al.  Generation of spatially broadband twin beams for quantum imaging. , 2007, Physical review letters.

[10]  R. Pooser,et al.  Entangled Images from Four-Wave Mixing , 2008, Science.

[11]  S. Tan.  Confirming entanglement in continuous variable quantum teleportation , 1999 .

[12]  V. Boyer,et al.  Strong low-frequency quantum correlations from a four-wave-mixing amplifier , 2008 .

[13]  Reid,et al.  Demonstration of the Einstein-Podolsky-Rosen paradox using nondegenerate parametric amplification. , 1989, Physical review. A, General physics.

[14]  D. Akamatsu,et al.  Storage and retrieval of a squeezed vacuum. , 2007, Physical review letters.

[15]  E. Arimondo,et al.  Ultraslow propagation of matched pulses by four-wave mixing in an atomic vapor. , 2007, Physical review letters.

[16]  Philippe Grangier,et al.  Quantum cloning and teleportation criteria for continuous quantum variables , 2001 .

[17]  Alan E. Willner,et al.  Maximum time delay achievable on propagation through a slow-light medium , 2005 .

[18]  R. Boyd,et al.  Wide-bandwidth, tunable, multiple-pulse-width optical delays using slow light in cesium vapor. , 2007, Physical review letters.

[19]  E. Polzik,et al.  Quantum memory for images: A quantum hologram , 2007, 0704.1737.

[20]  A Kuzmich,et al.  Multiplexed memory-insensitive quantum repeaters. , 2007, Physical review letters.

[21]  M. Lukin,et al.  Electromagnetically induced transparency with tunable single-photon pulses , 2005, Nature.

[22]  D. Korystov,et al.  Quantum memory for squeezed light. , 2007, Physical review letters.

[23]  D. Matsukevich,et al.  Storage and retrieval of single photons transmitted between remote quantum memories , 2005, Nature.

[24]  Preservation of entanglement in a slow light medium , 2008, 2008 Conference on Lasers and Electro-Optics and 2008 Conference on Quantum Electronics and Laser Science.

[25]  S. Braunstein,et al.  Quantum Information with Continuous Variables , 2004, quant-ph/0410100.

[26]  S. Harris,et al.  Light speed reduction to 17 metres per second in an ultracold atomic gas , 1999, Nature.

[27]  Experimental characterization of continuous-variable entanglement , 2003, quant-ph/0309013.

[28]  A. Galindo,et al.  Information and computation: Classical and quantum aspects , 2001, quant-ph/0112105.

[29]  J. Laurat,et al.  Mapping photonic entanglement into and out of a quantum memory , 2007, Nature.