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Using a spontaneous-down-conversion photon source, we produce true nonmaximally entangled states, i. e. , without the need for postselection. The degree and phase of entanglement are readily tunable, and are characterized both by a standard analysis using coincidence minima, and by quantum state tomography of the two-photon state. Using the latter, we experimentally reconstruct the reduced density matrix for the polarization. Finally, we use these states to measure the Hardy fraction, obtaining a result that is 122 from any local-realistic result.
White et al. (Mon,) studied this question.