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Quantum Electronics and Laser Science Conference

Tunable Bell-inequality violations in parametric downconversion

Thomas E. Kiess, Yanhua H. Shih, Alexander V. Sergienko, Morton H. Rubin, C. O. Alley

Published May 22, 1995• 0 citations
Publisher

Abstract

We prepare two-photon quantum states by using type-II phase matching in parametric downconversion to exhibit an interference term of variable strength. This interference, set by the selection of bandwidth of interference filters used in front of two detectors, is of quantum origin. We document this by exhibiting Bell-inequality violations.

DOI
10.13016/m27vn8-5kpe

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We prepare two-photon quantum states by using type-II phase matching in parametric downconversion to exhibit an interference term of variable strength. This interference, set by the selection of bandwidth of interference filters used in front of two detectors, is of quantum origin. We document this by exhibiting Bell-inequality violations.
We use a tunable quantum interference in type-II parametric down-conversion to construct two-photon quantum states that exhibit less-than-maximal, and tunable, violations of Bell-type inequalities. These states, no longer singlet-state analogs, possess an interference term of controllable magnitude that we adjust by tuning the measurement bandwidth. We show violations of two Bell-type inequalities in polarization variables, one more general than the other. We use these tunable violations to probe the threshold degree of interference that must be present to generate a violation, using an appropriate quantitative figure of merit.
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Simultaneous entanglement in spin and space-time of a two-photon quantum state generated in type-II spontaneous parametric down-conversion is demonstrated by the observation of quantum interference with 98% visibility in simple beam-splitter (Hanburry Brown-Twiss) anticorrelation and quantum beating experiments. The cancellation of two-photon probability amplitudes as a result of this double entanglement allow us to demonstrate two different types of Bell's inequality violations in one experimental setup.