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Physical Review Letters

Indistinguishable Photon Pairs from Independent True Chaotic Sources

Amir Nevet, Alex Hayat, Pavel Ginzburg, Meir Orenstein

Published Dec 16, 2011• 23 citations
Publisher

Abstract

Indistinguishability of events in quantum mechanics is manifested by interference between their probability amplitudes. We report a unique kind of interference occurring between indistinguishable events of photon-pair emission, where each photon of the pair is emitted from a distinct true chaotic light source and has a different energy. The indistinguishability results in an interference which is observed as an ultrafast modulation of the second-order coherence function, measured on a femtosecond time scale by two-photon absorption in a semiconductor photomultiplier tube.

DOI
10.1103/physrevlett.107.253601

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Indistinguishability of events in quantum mechanics is manifested by interference between their probability amplitudes. We report a unique kind of interference occurring between indistinguishable events of photon-pair emission, where each photon of the pair is emitted from a distinct true chaotic light source and has a different energy. The indistinguishability results in an interference which is observed as an ultrafast modulation of the second-order coherence function, measured on a femtosecond time scale by two-photon absorption in a semiconductor photomultiplier tube.
We have observed a nontrivial spatial correlation and anti-correlation from a ∼200 femtosecond pulsed chaoticthermal source. The classical picture of statistical correlation of intensity fluctuations fails to give an adequate interpretation. In the view of quantum mechanics these observations are the result of two-photon interference, involving the superposition of two-photon amplitudes, nonclassical entities corresponding to different yet indistinguishable alternative ways of triggering a joint-detection event.
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We wish to report an experimental observation of anti-correlation from first-order incoherent classical chaotic light. We explain why the classical statistical theory does not apply and provide a quantum interpretation. In quantum theory, either correlation or anti-correlation is a two-photon interference phenomenon, which involves the superposition of two-photon amplitudes, a nonclassical entity corresponding to different yet indistinguishable alternative ways of producing a joint-photodetection event.
We demonstrate a novel second-order spatial interference effect between two indistinguishable pairs of disjoint optical paths from a single chaotic source.Beside providing a deeper understanding of the physics of multi-photon interference and coherence, the effect enables retrieving information on both the spatial structure and the relative position of two distant double-pinhole masks, in the absence of first order coherence.We also demonstrate the exploitation of the phenomenon for simulating quantum logic gates, including a controlled-NOT gate operation.