Hardy's nonlocality proof using twisted photons.

Hardy's nonlocality proof is considered as "the best version of Bell's theorem". We report an experimental implementation of this by measuring the orbital angular momentum (OAM) of entangled twisted photon pairs. Two advantages arise from using twisted photons. First, the limited OAM spectrum generated by parametric down-conversion provides a natural set of OAM non-maximally entangled states with selective degrees of entanglement. Second, the measurement of any non-trivial superposition of OAM states can be conveniently done with spatial light modulators. We measure states that are defined on asymmetric OAM Bloch spheres and show results which are incompatible with local realism.

[1]  A. Yao.  Angular momentum decomposition of entangled photons with an arbitrary pump , 2010, 1012.5021.

[2]  Stephen M. Barnett,et al.  Entanglement of arbitrary superpositions of modes within two-dimensional orbital angular momentum state spaces , 2010 .

[3]  L. Hardy,et al.  Nonlocality for two particles without inequalities for almost all entangled states. , 1993, Physical review letters.

[4]  M Ritsch-Marte,et al.  Violation of a Bell inequality in two-dimensional orbital angular momentum state-spaces. , 2009, Optics express.

[5]  M. Genovese.  Research on hidden variable theories: A review of recent progresses , 2005, quant-ph/0701071.

[6]  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.

[7]  M. Padgett,et al.  Advances in optical angular momentum , 2008 .

[8]  J. P. Torres,et al.  Quantum spiral bandwidth of entangled two-photon states , 2003 .

[9]  Robert W. Boyd,et al.  Quantum Correlations in Optical Angle–Orbital Angular Momentum Variables , 2010, Science.

[10]  M J Padgett,et al.  Poincaré-sphere equivalent for light beams containing orbital angular momentum. , 1999, Optics letters.

[11]  Jordan.  Testing Einstein-Podolsky-Rosen assumptions without inequalities with two photons or particles with spin 1/2. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[12]  F. De Martini,et al.  Experimental test of the violation of local realism in quantum mechanics without Bell inequalities , 1997 .

[13]  A. Zeilinger,et al.  Entanglement in mutually unbiased bases , 2011, 1102.2080.

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

[15]  M. J. Padgett,et al.  Increasing the dimension in high-dimensional two-photon orbital angular momentum entanglement , 2012, 1205.1968.

[16]  David Branning,et al.  Experimental demonstration of the violation of local realism without Bell inequalities , 1995 .

[17]  Mark R. Dennis,et al.  Isolated optical vortex knots , 2010 .

[18]  M. Barbieri,et al.  Towards a test of non-locality without "supplementary assumptions" , 2005 .

[19]  J. Bell.  On the Problem of Hidden Variables in Quantum Mechanics , 1966 .

[20]  N. David Mermin,et al.  The Best Version of Bell's Theorem a , 1995 .

[21]  S. Goldstein,et al.  Nonlocality without inequalities for almost all entangled states for two particles. , 1994, Physical review letters.

[22]  A. Vaziri,et al.  Entanglement of the orbital angular momentum states of photons , 2001, Nature.

[23]  F. De Martini,et al.  LADDER PROOF OF NONLOCALITY WITHOUT INEQUALITIES : THEORETICAL AND EXPERIMENTAL RESULTS , 1997 .

[24]  G. Vallone,et al.  Testing Hardy's nonlocality proof with genuine energy-time entanglement , 2011 .