Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise.

We present an experiment demonstrating the entanglement enhanced capacity of a quantum channel with correlated noise, modeled by a fiber optic link exhibiting fluctuating birefringence. In this setting, introducing entanglement between two photons is required to maximize the amount of information that can be encoded into their joint polarization degree of freedom. We demonstrated this effect using a fiber-coupled source of entangled photon pairs based on spontaneous parametric down-conversion, and a linear-optics Bell state measurement. The obtained experimental classical capacity with entangled states is equal to 0.82+/-0.04 per a photon pair, and it exceeds approximately 2.5 times the theoretical upper limit when no quantum correlations are allowed.

[1]  C. Macchiavello,et al.  Entanglement-enhanced information transmission over a quantum channel with correlated noise , 2001, quant-ph/0107052.

[2]  S. Mancini,et al.  Quantum channels with a finite memory , 2003, quant-ph/0305010.

[3]  Weinfurter,et al.  Dense coding in experimental quantum communication. , 1996, Physical review letters.

[4]  W. Wootters,et al.  Optimal detection of quantum information. , 1991, Physical review letters.

[5]  Y. Nambu,et al.  Generation of polarization-entangled photon pairs in a cascade of two type-I crystals pumped by femtosecond pulses , 2002 .

[6]  A. G. White,et al.  Experimental verification of decoherence-free subspaces. , 2000, Science.

[7]  J. Bell.  On the Einstein-Podolsky-Rosen paradox , 1964 .

[8]  Gisin,et al.  Quantum cryptography using entangled photons in energy-time bell states , 1999, Physical review letters.

[9]  Ekert,et al.  Quantum cryptography based on Bell's theorem. , 1991, Physical review letters.

[10]  Masahide Sasaki,et al.  Exceeding the classical capacity limit in a quantum optical channel. , 2003, Physical review letters.

[11]  White,et al.  Entangled state quantum cryptography: eavesdropping on the ekert protocol , 1999, Physical review letters.

[12]  S. Lloyd,et al.  Classical capacity of the lossy bosonic channel: the exact solution. , 2003, Physical review letters.

[13]  Mann,et al.  Measurement of the Bell operator and quantum teleportation. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[14]  S. V. Enk,et al.  Experimental Proposal for Achieving Superadditive Communication Capacities with a Binary Quantum Alphabet , 1999, quant-ph/9903039.

[15]  Hong,et al.  Measurement of subpicosecond time intervals between two photons by interference. , 1987, Physical review letters.

[16]  T. Rudolph,et al.  Classical and quantum communication without a shared reference frame. , 2003, Physical review letters.

[17]  Peter W. Shor,et al.  Quantum Information Theory , 1998, IEEE Trans. Inf. Theory.

[18]  Konrad Banaszek,et al.  Exploiting entanglement in communication channels with correlated noise (9 pages) , 2003, quant-ph/0309148.

[19]  I. Chuang,et al.  Quantum Computation and Quantum Information: Bibliography , 2010 .

[20]  C. Caves,et al.  Quantum limits on bosonic communication rates , 1994 .

[21]  Weinfurter,et al.  Quantum cryptography with entangled photons , 1999, Physical review letters.