Abstract
We examine experimentally how the degree of position-momentum entanglement of photon pairs depends on the transverse coherence of the pump beam that excites them in a process of spontaneous parametric down-conversion. Using spatially incoherent light from a light-emitting diode, we obtain strong position correlation of the photons, but we find that transverse momentum correlation, and thus entanglement, is entirely absent. When we continuously vary the degree of spatial coherence on the pump beam, we observe the emergence of stronger momentum correlations and entanglement. We present theoretical arguments that explain our experimental results. Our results shed light on entanglement generation and can be applied to control entanglement for quantum information applications.
Highlights
3current address: Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria
Entangled photons have become a standard tool in quantum information [3] and foundations [4, 5]
An impressive example is position-momentum entanglement of photon pairs [6], explained heuristically through the correlations implied by a common birth zone and momentum conservation
Summary
The influence of pump coherence on the generation of position-momentum entanglement in down-conversion Enno Giese,2, 4, ∗ Lixiang Chen,1, † and Robert W. Position-momentum-entangled photon pairs can be rather straight-forwardly generated in spontaneous parametric down-conversion (SPDC) [6, 16], the workhorse of many quantum optics labs.
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Published Version
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