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Optics Letters

Observation of a generalized bunching effect of six photons

Xiao-Ling Niu, Yan-Xiao Gong, Bi‐Heng Liu, Yun‐Feng Huang, Guang‐Can Guo, Z. Y. Ou

Published Apr 15, 2009• 24 citations
Publisher

Abstract

When photons are indistinguishably in the same temporal mode, their detection probability is greatly enhanced due to constructive multiphoton interference, as compared to the case when they are distinguishable. We observed for what is believed to be the first time such a photon bunching effect for six photons. The observed enhancement factor in six-photon coincidence measurement is 17+/-2, which is close to a factor of 20 for an ideal case. Our result confirms that the six photons that we obtain have a high degree of indistinguishability.

DOI
10.1364/ol.34.001297

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When photons are indistinguishably in the same temporal mode, their detection probability is greatly enhanced due to constructive multiphoton interference, as compared to the case when they are distinguishable. We observed for what is believed to be the first time such a photon bunching effect for six photons. The observed enhancement factor in six-photon coincidence measurement is 17+/-2, which is close to a factor of 20 for an ideal case. Our result confirms that the six photons that we obtain have a high degree of indistinguishability.
We present a multimode model to describe an arbitrary NNN-photon state with a wide spectral range and some arbitrary temporal distribution. In general, some of the NNN photons are spread out in time while others may overlap and become indistinguishable. From this model, we find that the temporal (in)distinguishability of photons is related to the exchange symmetry of the multiphoton wave function. We find that simple multiphoton detection scheme gives rise to a more general photon bunching effect with the famous two-photon effect as a special case. We then send this NNN-photon state into a recently discovered multiphoton interference scheme. We calculate the visibility of the multiphoton interference scheme and find that it is related to the temporal distinguishability of the NNN photons. Maximum visibility of one is achieved for the indistinguishable NNN-photon state whereas the visibility degrades when some of the photons are separated and become distinguishable. Thus we can identify an experimentally measurable quantity that may quantitatively define the degree of indistinguishability of an NNN-photon state. This presents a quantitative demonstration of the complementary principle of quantum interference.
We present a multi-mode model to describe an arbitrary N-photon state with a wide spectral range and some arbitrary temporal distribution. In general, some of the NNN photons are spread out in time while other may overlap and become indistinguishable. From this model, we find that the temporal (in)distinguishability of photons is related to the exchange symmetry of the multi-photon wave function. We find that simple multi-photon detection scheme gives rise to a more general photon bunching effect with the famous two-photon effect as a special case. We then send this N-photon state into a recently discovered multi-photon interference scheme. We calculate the visibility of the multi-photon interference scheme and find that it is related to the temporal distinguishability of the NNN photons. Maximum visibility of one is achieved for the indistinguishable N-photon state whereas the visibility degrades when some of the photons are separated and become distinguishable. Thus we can identify an experimentally measurable quantity that may quantitatively define the degree of indistinguishability of an N-photon state. This presents a quantitative demonstration of the complementary principle of quantum interference.
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The discovery of photon bunching effect is an important milestone of quantum optics.The attempt to explain it leads to the development of the techniques in quantum optics.Nowadays,it′s thought that the physics behind the photon bunching effect in the second-order coherence is two-photon interference.This paper shows that there are similar generalized bunching effects in higher-order coherence.We also claim that the generalized photon bunching effect is a result of multi-photon interference due to indistinguishability of photons.In some typical optical circuit,N-photon interference can let the enhancement factor be up to N!.
Photon bunching effect and stimulated emission of single photons is investigated and observed in the parametric amplification process. It is found that the two-photon interference is responsible for the photon bunching effect and stimulated emission, which is discussed in the temporal degree of freedom and in the presence of photon losses. Moreover, the direct measurement of the indistinguishability of two signal photons without any filtering is accomplished via the correlation between the two idler photons from two cascaded parametric down-conversion processes. This result shows that photon indistinguishability plays an essential role in stimulated emission.
Bosonic bunching is a term used to describe the well-known tendency of bosons to bunch together, and which differentiates their behavior from that of fermions or classical particles. However, in some situations, perfectly indistinguishable bosons may counter-intuitively bunch less than classical, distinguishable particles. Here, we report two such counter-intuitive multiphoton bunching effects observed with three photons in a three-mode balanced photonic Fourier interferometer. In this setting, we show that indistinguishable photons actually minimize the probability of bunching. We also show that any non-trivial value of the three-photon collective photonic phase leads to a decreased probability of all photons ending up in the same mode, even as we increase pairwise indistinguishability. Our experiments feature engineering of partial indistinguishability scenarios using both the time and the polarization photonic degrees of freedom, and a polarization-transparent 8-mode tunable interferometer with a quantum-dot source of single photons. Besides the foundational understanding, the observation of these counter-intuitive phenomena open news perspective in devising more efficient ways of routing photons for advantage in metrology and quantum computation.