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Spotlight on Optics


  • April 2014

Optics InfoBase > Spotlight on Optics > Third-order antibunching from an imperfect single-photon source

Third-order antibunching from an imperfect single-photon source

Published in Optics Express, Vol. 22 Issue 3, pp.3244-3260 (2014)
by Martin J. Stevens, Scott Glancy, Sae Woo Nam, and Richard P. Mirin

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Spotlight summary: The development of reliable single-photon sources is currently a priority, since such sources are an essential ingredient for a variety of quantum-enhanced technologies, ranging from quantum cryptography to quantum computing. In the quest for high-quality single photon sources, the development of techniques that may permit a full characterization of source properties is a highly important research area.

The usual criterion for determining single-photon source quality is the degree to which the second order correlation function g(2) evaluated at zero temporal delay approaches the ideal value of zero. It is very interesting to learn from M. Stevens et al. that the picture painted by a measurement of g(2) is at best a partial picture. Indeed, this paper shows that the multi-photon events including three or more photons play a significant role.

The authors present an analysis of a Hanbury Brown-Twiss interferometer, as well as of a three-detector version of such an interferometer, showing that if the probability of progressively higher-order photon-number emission falls sufficiently fast, the histograms obtained from click detectors---i.e. those which are not photon-number resolving---approach well the ideal g(2) and g(3) functions. Armed with this analysis, the authors go on to present data for a “single” photon source based on a quantum dot embedded in a micro-cavity, both in the CW-pump and pulsed-pump regimes. The authors have exploited the power of modern time-tagging electronics in order to obtain comprehensive data for g(2) as a function of delay and of g(3) as a function of the two relevant delays.

While it is highly interesting to appreciate the full three-dimensional structure of the g(3) function, which exhibits a non-trivial structure in both the CW and pulsed regimes, the main conclusion of this paper relates to the inferred nature of the single-photon source. The authors propose a model for the source as an ideal single photon source showing perfect anti-bunching, incoherently mixed with a source characterized by Poissonian photon number statistics related to the cavity itself. The authors show that their simultaneous measurements of g(2) and g(3) are indeed consistent with this model. In order to further substantiate the validity of this model, a spectrally-resolved cross-correlation measurement was performed. It is shown that frequencies outside the quantum-dot emission peak are uncorrelated to frequencies at the peak. This lends credence to the model of the source as two independent emitters.

Most previous characterizations of single-photon sources have operated under the assumption that three-photon and higher photon number emission can be safely disregarded. On the one hand, this work shows clearly that the three-photon terms have an important impact on the source properties. On the other hand, this paper shows that measuring both two-photon and three-photon correlation functions leads to a better understanding of the nature of the source itself.

--Alfred U’Ren

Technical Division: Information Acquisition, Processing, and Display
ToC Category: Coherence and Statistical Optics
OCIS Codes: (030.5260) Coherence and statistical optics : Photon counting
(270.1670) Quantum optics : Coherent optical effects
(270.5290) Quantum optics : Photon statistics

Posted on April 21, 2014

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