Single-photon sources are key components of a quantum communication network; however, present-day realizations of such photon sources do not yet show an ideal behavior. A quantitative way to qualify them is by calculating the second order correlation function, as done in the Hanbury Brown-Twiss (HBT) experiment [1]. In this study a Bell-source that produces an entangled Bell sate was used as a single-photon source. When one branch is used as heralding for the other the source produces sub-Poisson photon statistics. This is not true for the non-heralded case. While conducting the HBT experiment in the non-heralded case we came across a phenomenon of double coincidence peaks. Through our study we found that this could be a result of two very distinct phenomenon, one of which is due to the non-ideal behavior of a single-photon source, the other due to secondary photons generated by single-photon avalanche diodes (SPADs). Both an ideal sub-Poisson statistic and the double coincidence peaks result in g(2)(0) = 0 by the HBT experiment, but in the first case the photon source is indeed an actual single-photon source, while in the second case this could also happen with a non-ideal single-photon source. For that reason, sometimes it is not sufficient to rely only on the HBT experiment to qualify a single-photon source, but also conduct some deeper experiments.
Single-photon sources are key components of a quantum communication network; however, present-day realizations of such photon sources do not yet show an ideal behavior. A quantitative way to qualify them is by calculating the second order correlation function, as done in the Hanbury Brown-Twiss (HBT) experiment [1]. In this study a Bell-source that produces an entangled Bell sate was used as a single-photon source. When one branch is used as heralding for the other the source produces sub-Poisson photon statistics. This is not true for the non-heralded case. While conducting the HBT experiment in the non-heralded case we came across a phenomenon of double coincidence peaks. Through our study we found that this could be a result of two very distinct phenomenon, one of which is due to the non-ideal behavior of a single-photon source, the other due to secondary photons generated by single-photon avalanche diodes (SPADs). Both an ideal sub-Poisson statistic and the double coincidence peaks result in g(2)(0) = 0 by the HBT experiment, but in the first case the photon source is indeed an actual single-photon source, while in the second case this could also happen with a non-ideal single-photon source. For that reason, sometimes it is not sufficient to rely only on the HBT experiment to qualify a single-photon source, but also conduct some deeper experiments.
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.
Single-photon sources are at the heart of quantum-optical networks, with their uniquely quantum emission and phenomenon of two-photon interference allowing for the generation and transfer of nonclassical states. Although a few analytical methods have been briefly investigated for describing pulsed single-photon sources, these methods apply only to either perfectly ideal or at least extremely idealized sources. Here, we present the first complete picture of pulsed single-photon sources by elaborating how to numerically and fully characterize non-ideal single-photon sources operating in a pulsed regime. In order to achieve this result, we make the connection between quantum Monte-Carlo simulations, experimental characterizations, and an extended form of the quantum regression theorem. We elaborate on how an ideal pulsed single-photon source is connected to its photocount distribution and its measured degree of second- and first-order optical coherence. By doing so, we provide a description of the relationship between instantaneous source correlations and the typical experimental interferometers (Hanbury-Brown and Twiss, Hong–Ou–Mandel, and Mach–Zehnder) used to characterize such sources. Then, we use these techniques to explore several prototypical quantum systems and their non-ideal behaviors. As an example numerical result, we show that for the most popular single-photon source—a resonantly excited two-level system—its error probability is directly related to its excitation pulse length. We believe that the intuition gained from these representative systems and characters can be used to interpret future results with more complicated source Hamiltonians and behaviors. Finally, we have thoroughly documented our simulation methods with contributions to the Quantum Optics Toolbox in Python in order to make our work easily accessible to other scientists and engineers.
Emitters of single photons are essential resources for emerging quantum technologies and developed within different platforms including nonlinear optics and atomic and solid-state systems. The energy-level structures of emission processes are critical for reaching and controlling high-quality sources. The most commonly applied test uses a Hanbury Brown and Twiss (HBT) setup to determine the emitter energy-level structure based on fitting temporal correlations of photon detection events. However, only partial information about the emission process is extracted from such detection, that might be followed by an inconclusive fitting of the data. This process predetermines our limited ability to quantify and understand the dynamics in the photon emission process that are of importance for the applications in communication, sensing, and computing. In this work, we present a complete analysis based on all normalized coincidences between detection and no-detection events recorded in the same HBT setup to certify expected properties of an emitted photonic state. As a proof of concept we apply our methodology to single nitrogen-vacancy centers in diamond, in which case the certification conclusively rejects a model based on a two-level emitter that radiates a photonic state mixed with any classical noise background. Published by the American Physical Society 2024
The authors report a “plug and play” source of single photons, with full integration to a single-mode optical fiber. One end of the fiber is attached to the top of an InGaAs∕GaAs quantum dot wafer. The other end is connected via a wavelength-division multiplexing system to two separate fibers: one for carrying excitation light and the other for emitted light. A Hanbury-Brown and Twiss [Nature (London) 77, 27 (1956)] measurement was performed on the emission from single excitons recombining in the quantum dots. A second-order correlation function at zero time delay of approximately 0.01 indicates a nearly ideal source of single photons. The maximum variation of peak position over 24days is less than 0.1nm.
The article surveys the state of the art in the design, development and application of devices for deterministically generating single photons on demand. Both the defined function and requisite form of such ‘single-photon’ sources are explained in detail. Their attributes and characteristics, in particular the photon-counting statistics of the light that they generate, are presented in conjunction with the experimental apparatus (most notably the Hanbury-Brown and Twiss interferometer) for measuring them. Promising applications of single-photon sources within quantum key distribution, quantum information processing, as well as metrology and fundamental tests of quantum mechanics, are described. The utility and relative advantages of single-photon sources vis-á-vis more conventional sources of light are explained in terms of application-specific requirements and the respective abilities of different sources to fulfil them. The article collects, classifies and sorts the most significant work towards realizing practical single-photon sources to date. Though emanating from a diverse set of technological disciplines, with different research and application objectives in mind, the relative advantages and drawbacks of each approach are assessed, to give the reader a broad yet coherent and critical review of a rapidly developing research front.
Hanbury Brown and Twiss (HBT) effect has broad applications in optics and other branches of physics, and traditionally this effect is considered in pure spatial or temporal domain. Here we investigate the spatiotemporal HBT effect, extending this phenomenon from spatial or temporal to spatiotemporal domain. By assuming the Gaussian statistics of partially coherent spatiotemporal pulsed sources, we find the generalized analytical results for spatiotemporal HBT effect in the compact form, with the help of the matrix-optics method, which can consider the HBT effect in spatial and temporal domain simultaneously. Furthermore, for Gaussian Schell-model pulsed beams (GSMPBs) used as a spatiotemporal correlated source, we have obtained the generalized expression to calculate spatiotemporal HBT effect, which is useful for up to three-dimensional cases in any second-order linear dispersive medium. By taking a simple two-dimensional case and using air as an example of a linear dispersive medium, we numerically illustrate the properties of the spatiotemporal HBT effect by adjusting the spatial and temporal parameters of the GSMPB source, and reveal the influence of both the spatial and temporal parameters on the spatiotemporal HBT effect. This work paves the path towards the detailed study of HBT effect for a source containing spatiotemporal information with Gaussian statistics.