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Coherence of a quantum dot source of entangled photons

Research output: Contribution to conference - Without ISBN/ISSN Abstract

Published
Publication date2008
Original languageEnglish
Event8th Internation Conference on Physics of Light-Matter Coupling in Nanostructures - Tokyo, Japan
Duration: 7/04/2008 → …

Conference

Conference8th Internation Conference on Physics of Light-Matter Coupling in Nanostructures
CountryJapan
CityTokyo
Period7/04/08 → …

Abstract

A well controlled, triggered source of entangled photons is desirable for many applications in quantum information processing. The two-photon cascade from a biexciton state, two electrons and holes, confined in a quantum dot can be such a source of polarisation-entangled photons provided the two decay paths from the biexciton carry no “which-path” information. In recent years many techniques have been employed to make the two optical decay paths from the biexciton state indistinguishable. We will demonstrate the effect of the exciton fine-structure splitting on a single-dot based entangled photon source. Surprisingly the entanglement is found to persist despite relatively large separations between the intermediate energy levels of up to 4µeV. Measurements demonstrate that entanglement of the photon pair is robust to the dephasing of the intermediate exciton state responsible for the first order coherence time of either of the single photons. We distinguish between the first-order coherence time (2*), and a parameter defined as the cross-coherence time (HV) which is illustrated in the figure. The cross-coherence time is found to be at least an order of magnitude greater than the first-order coherence time.

We will also report on recent progress towards an ideal source of triggered polarisation-entangled photons with a single quantum dot.