Usually HBT effect can be interpreted by classical (intensity fluctuation correlation) and quantum (interference of two-photon probability amplitudes) theories properly at the same time. In this manuscript, we report a deliberately designed experiment in which two chaotic light beams has the same intensity fluctuation but mutual-orthogonal polarizations to each other so there will be no interference of two-photon probability amplitudes. Classical and quantum theory give different predictions on if there should be HBT (photon bunching) effect or not in the experiment. The experiment results are used to test the two different predictions. At the end, both the temporal and spatial HBT effects are observed.
Usually HBT effect can be interpreted by classical (intensity fluctuation correlation) and quantum (interference of two-photon probability amplitudes) theories properly at the same time. In this manuscript, we report a deliberately designed experiment in which two chaotic light beams has the same intensity fluctuation but mutual-orthogonal polarizations to each other so there will be no interference of two-photon probability amplitudes. Classical and quantum theory give different predictions on if there should be HBT (photon bunching) effect or not in the experiment. The experiment results are used to test the two different predictions. At the end, both the temporal and spatial HBT effects are observed.
From quantum point of view, Hanbury Brown-Twiss effect is a result of constructive-destructive two-photon interference. There should be no Hanbury Brown-Twiss effect if there was no two-photon interference. In this paper, we observed Hanbury Brown- Twiss effect in a specially designed experiment, in which two-photon interference is impossible by keeping only one two-photon probability amplitude in the experimental scheme. However, our experimental results can still be interpreted by Glauber's quantum optical coherence theory. The researches in our paper are helpful to understand the physics of the second-order coherence of light, especially the physics of Hanbury Brown-Twiss effect.
The Hanbury Brown–Twiss (HBT) effect, at the quantum level, is essentially an interference of one particle with another, as opposed to interference of a particle with itself. Conventional treatments of identical particles encounter difficulties while dealing with entanglement. A recently introduced label-free approach to indistinguishable particles is described, and is used to analyze the HBT effect. Quantum wave-packets have been used to provide a better understanding of the quantum interpretation of the HBT effect. The effect is demonstrated for two independent particles governed by Bose–Einstein or Fermi–Dirac statistics. The HBT effect is also analyzed for pairs of entangled particles. Surprisingly, entanglement has almost no effect on the interference seen in the HBT effect. In the light of the results, an old quantum optics experiment is reanalyzed, and it is argued that the interference seen in that experiment is not a consequence of non-local correlations between the photons, as is commonly believed. Quanta 2017; 6: 61–69.
Quantum entanglement enables a wide range of fundamental studies and practical applications in quantum optics, computing, and communication. In this work, we investigate two-photon interference using position-momentum entangled photons generated via Type-II Spontaneous Parametric Down-Conversion (SPDC). By employing a double-slit setup, we explore two distinct quantum interference phenomena: the Hanbury Brown and Twiss (HBT) effect, where the photons pass through different slits, and NOON-state interference, where both photons traverse the same slit. We deterministically separate the two photons based on their orthogonal polarizations and demonstrate that both interference effects persist despite their distinguishability at the detectors. This result goes beyond the conventional understanding of two-photon interference and reveals a novel nonlocal HBT effect, where interference occurs even in the absence of spatial overlap, and is rooted in entanglement. Our findings deepen the understanding of quantum interference and open new avenues for applications in quantum optics and precision measurement.
The Hanbury Brown–Twiss (HBT) interferometer, which is used to measure the correlation of two photons or two light beams, has played a crucial role in quantum optics and quantum information. We propose a generalized HBT interferometer, which is able to measure the correlation of photons or light beams up to eight in a single experimental run. With an improved time correlated single-photon counting (TCSPC) algorithm, two-, three-, and four-photon coincidence counts, and the degree of fifth-order coherence of pseudothermal light are measured with a data collection time of 60 s. The generalized HBT interferometer can be used to measure the correlation of two multi-photon detection events by simulating photon number resolving detectors with multiple single-photon detectors. The generalized HBT interferometer and improved TCSPC algorithm provide a versatile framework for studying multi-photon correlations and interference, which is helpful to understand the physics of multi-photon interference and may find applications in fluorescence lifetime imaging and other techniques using TCSPC.
We report on the two-photon superbunching effect of thermal light via constructive multiple two-photon path interference, showing the possibility of controlling the bunching property of thermal light in a linear optical system. By inserting n pairs of mutually first-order incoherent optical channels as a cascade into the traditional Hanbury Brown and Twiss (HBT) interferometer, the two-photon bunching peak-to-background ratio of thermal light can be increased by up to $2\ifmmode\times\else\texttimes\fi{}1.{5}^{n}$, surpassing the theoretical upper limit of 2 for a traditional HBT interferometer. Experimentally, the ratio was measured to be $2.4\ifmmode\pm\else\textpm\fi{}0.1$ when one pair of optical channels was inserted. Such a scheme can be viewed as a prototype of a two-photon grating.
Quantum opticians usually employ and exploit genuine or modified HBT setups as standard tools for characterizing non-classical states of light. One the one hand, HBT measurements permit to characterize the emission statistics of photonic modes that are, depending on the emitter and on the spatial and spectral features, thermal, poissonnian, sub-poissonnian, or deterministic. On the other hand, auto-correlation and cross-correlation functions, recorded in the single photon counting regime, permit to infer the unique properties of single photon and two photons sources, that are further utilized in quantum communication applications. For instance, when applied to a single photon source, a genuine HBT setup helps qualifying the uniqueness emission feature. Moreover, when applied to a two photon source, a modified HBT setup permits measuring simultaneous emission time correlations, as well as single photon coherence time. During this talk, I will review some situations in which HBT type setups and related measurements are exploited in and for quantum optics or communication experiments.