Characterizing multi-photon quantum interference with practical light sources and threshold single-photon detectors

Abstract

The experimental characterization of multi-photon quantum interference effects in optical networks is essential in many applications of photonic quantum technologies, which include quantum computing and quantum communication as two prominent examples. However, such characterization often requires technologies which are beyond our current experimental capabilities, and todayʼs methods suffer from errors due to the use of imperfect sources and photodetectors. In this paper, we introduce a simple experimental technique to characterize multi-photon quantum interference by means of practical laser sources and threshold single-photon detectors. Our technique is based on well-known methods in quantum cryptography which use decoy settings to tightly estimate the statistics provided by perfect devices. As an illustration of its practicality, we use this technique to obtain a tight estimation of both the generalized Hong−Ou−Mandel dip in a beamsplitter with six input photons and the three-photon coincidence probability at the output of a tritter.

Bounding the outcome of a two-photon interference measurement using weak coherent states

“…where P (1, 1|1, 1) c = 1/2 is the predicted value for classical particles [10]. We find that V = 0.995 +0.005 −0.013 , which is comparable to the best of any experimental observation.…”

“…This is likely due to the higher-order terms ignored when deriving the upper bound. The accuracy of the bound can be improved using additional states with intermediate photon numbers [9,10], which we will explore in future work. However, even with this increase, P (1, 1|1, 1) ub 1/2.…”

Estimating the photon-number distribution of photonic channels with realistic devices and applications in photonic quantum information processing

“…This direction was recently pursued by the authors of Ref. [34], who used the direct combination of decoy-state and detector-decoy methods to characterise multi-photon quantum interference patterns.…”

“…Our theoretical contributions are three-fold: (1) the extension of Ref. [34] to homodyne detectors, (2) the security analysis of practical QKD systems based on calibrated single-photon detectors, and (3) an experimental proposal to implement TCSPC technology using homodyne detectors instead of single-photon detectors. Concerning the latter, there are two practical advantages in using homodyne detectors: (1) these detectors are typically much more cost-effective than single-photon detectors and (2) no active intensity modulation is required to achieve the same effect as detector-decoy.…”

Single-photon characteristics of superposed weak coherent states

“…QKD), the multi-photon issue of WCS can be circumvented by the decoy state method [14][15][16], it requires a perfect random phase θ [17]. Recent attempts to yield single-photon behaviors from phase randomized WCS [18][19][20][21] are indirect observations through data reconstruction (but not the genuine exhibitions) of such behaviors. Therefore, what fundamentally constitutes the characteristics of single photons and how they can be modulated in the quantum optical framework are, in fact, still obscure.…”