Entanglement in cascaded-crystal parametric down-conversion.
We use spontaneous parametric down-conversion in a cascade of crystals, driven by a single monochromatic cw pump laser, to study the interference of entangled photon pairs. By changing the distance between the crystals, the observed quantum interference pattern varies continuously from that associated with a longer single crystal to that associated with independent emissions from two distinct crystals. Postselection via spectral filtering suppresses this phenomenon. These findings are expected to advance the field of quantum-state engineering.
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Quantum Imaging Laboratory, Department of Electrical & Computer Engineering, Boston University, 8 Saint Mary's Street, Boston, Massachusetts 02215, USA.
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Saleh
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Teich
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