Postselection-free energy-time entanglement.

We report a two-photon interference experiment that realizes a postselection-free test of Bell{close_quote}s inequality based on energy-time entanglement. In contrast with all previous experiments of this type, the employed entangled states are obtained {ital without} the use of a beam splitter or a short coincidence window to {open_quote}{open_quote}throw away{close_quote}{close_quote} unwanted amplitudes. A (95.0{plus_minus}1.4){percent} interference fringe visibility is observed, implying a strong violation of the Bell inequality. The scheme is very compact and has demonstrated excellent stability, suggesting that it may be useful, for example, in practical quantum cryptography. {copyright} {ital 1996 The American Physical Society.}

[1]  Ou,et al.  Violation of Bell's inequality and classical probability in a two-photon correlation experiment. , 1988, Physical review letters.

[2]  Aephraim M. Steinberg,et al.  High-visibility interference in a Bell-inequality experiment for energy and time. , 1993, Physical review. A, Atomic, molecular, and optical physics.

[3]  Matison,et al.  Experimental Test of Local Hidden-Variable Theories , 1972 .

[4]  P. Townsend,et al.  Quantum key distribution over distances as long as 30 km. , 1995, Optics letters.

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

[6]  Orel,et al.  Effects of open inelastic channels in the resonant dissociative recombination of HeH+ , 1995, Physical review letters.

[7]  Shih,et al.  New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion. , 1988, Physical review letters.

[8]  Albert Einstein,et al.  Can Quantum-Mechanical Description of Physical Reality Be Considered Complete? , 1935 .

[9]  J. Rarity,et al.  Single photon interference in 10 km long optical fibre interferometer , 1993 .

[10]  G. Roger,et al.  Experimental Test of Bell's Inequalities Using Time- Varying Analyzers , 1982 .

[11]  R. Glauber.  Coherent and incoherent states of the radiation field , 1963 .

[12]  Shih,et al.  Theory of two-photon entanglement in type-II optical parametric down-conversion. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[13]  Sleator,et al.  Realizable Universal Quantum Logic Gates. , 1995, Physical review letters.

[14]  Barenco,et al.  Conditional Quantum Dynamics and Logic Gates. , 1995, Physical review letters.

[15]  J. Franson,et al.  Quantum Cryptography Using Polarization Feedback , 1994 .

[16]  J. Rarity,et al.  Experimental violation of Bell's inequality based on phase and momentum. , 1990, Physical review letters.

[17]  Franson.  Two-photon interferometry over large distances. , 1991, Physical review. A, Atomic, molecular, and optical physics.

[18]  Kwiat.  Comment on "Reliability of Bell-inequality measurements using polarization correlations in parametric-down-conversion photon sources" , 1995, Physical review. A, Atomic, molecular, and optical physics.

[19]  J. Cirac,et al.  Quantum Computations with Cold Trapped Ions. , 1995, Physical review letters.

[20]  M. Żukowski,et al.  Bell's theorem: Proposition of realizable experiment using linear momenta , 1988 .

[21]  Rarity,et al.  Violation of Bell's inequality over 4 km of optical fiber. , 1994, Physical review letters.

[22]  Mann,et al.  Maximal violation of Bell inequalities for mixed states. , 1992, Physical review letters.

[23]  Aephraim M. Steinberg,et al.  Quantum non-locality in two-photon experiments at Berkeley , 1995 .

[24]  John Rarity,et al.  Quantum Random-number Generation and Key Sharing , 1994 .

[25]  J. Clauser.  EXPERIMENTAL INVESTIGATION OF A POLARIZATION CORRELATION ANOMALY , 1976 .

[26]  Santos.  Does quantum mechanics violate the Bell inequalities? , 1991, Physical review letters.

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

[28]  R. Glauber.  The Quantum Theory of Optical Coherence , 1963 .

[29]  Ou,et al.  Observation of nonlocal interference in separated photon channels. , 1990, Physical review letters.

[30]  De Caro L,et al.  Reliability of Bell-inequality measurements using polarization correlations in parametric-down-conversion photon sources. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[31]  A. Shimony,et al.  Two-particle interferometry. , 1989 .

[32]  Y. Shih,et al.  Experimental tests of Bell's inequalities based on space-time and spin variables. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[33]  Shih,et al.  New high-intensity source of polarization-entangled photon pairs. , 1995, Physical review letters.

[34]  Ekert,et al.  Practical quantum cryptography based on two-photon interferometry. , 1992, Physical review letters.

[35]  J. Brendel,et al.  Experimental Test of Bell's Inequality for Energy and Time , 1992 .

[36]  Franson,et al.  Bell inequality for position and time. , 1989, Physical review letters.

[37]  Teich,et al.  Two-photon interference in a Mach-Zehnder interferometer. , 1990, Physical review letters.