Hanbury Brown-Twiss correlations are a quantum effect, allowing astronomical interferometry over arbitrary baselines. We demonstrate resolving HBT measurements at multiple frequencies simultaneously with a fast single-photon detector array, promising greatly enhanced sensitivity.
The Hanbury Brown–Twiss (HBT) effect holds a pivotal place in intensity interferometry and gave a seminal contribution to the development of quantum optics. To observe such an effect, both good spectral and timing resolutions are necessary. Most often, the HBT effect is observed for a single frequency at a time due to its limitations in dealing with multifrequencies simultaneously, halting and limiting some applications. Here, we report a fast and data-driven spectrometer built with a one-dimensional array of single-photon-sensitive avalanche diodes. We report observing the HBT effect for multiple frequencies at the same time. In particular, we observe the HBT effect for up to five lines of the Ne spectrum, but this can be improved upon to include more lines. Our work represents a major step in making spectral binning and multifrequency HBT more widely available. The technology we present can benefit both classical and quantum applications.
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.
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.
The idea of exploiting quantum features of light to perform more precise astrophysical measurements is a long-desired goal of both the optics and astrophysics communities, but only recently have theoretical proposals started to be experimentally implemented. One important goal is to increase the baseline distance between telescopes in interferometry, and thus improve the angular resolution of the celestial object. Some of the earlier proposals rely on the use of quantum repeaters to connect the two baseline stations. However, another proposal employs other quantum optical approaches to circumvent the need for quantum repeaters, while still providing a quantum advantage. I will discuss the on-going project for building quantum-enhanced telescopes for precision astrometry, i.e., measurements of position and velocity of celestial objects. I will present a proof-of-principle experimental demonstration of a two-photon interferometer for such goal. Moreover, I will present a single-photon-sensitive spectrometer, based on a linear array of 512 single-photon avalanche diode detectors, with 0.04 nm spectral and 40 ps temporal resolutions. This device enables us to implement a spectral binning technique, essentially allowing us to perform multiple measurements together, because each frequency can be treated as an independent measurement. Such device could also be used in other applications. Lastly, I will report on our frequency-resolved Hanbury Brown-Twiss experiments. Our work represents an important step towards quantum telescopes.
Fast and precise spectrometers have numerous applications in quantum sciences, astronomy, and other fields. Thanks to the recent advances in the technology of single-photon detectors, their timing and spectral resolution approach fundamental limits dictated by the Heisenberg uncertainty principle (HUP) allowing new measurements, which were not possible before. In this work, we present a simple and fast spectrometer based on the LinoSPAD2 detector. With an array of 512 SPADs with a pixel size of 26 um2, we can achieve 0.1 nm/pixel spectral resolution with off-the-shelf optical components. Thanks to the 40 ps rms timing resolution of each SPAD, we can operate a factor of 10 above the HUP. We present measurements of the Hanbury Brown-Twiss effect at multiple frequencies using both the discrete spectral lines of a noble gas source and a broadband source of light (LED).
Hanbury-Brown and Twiss (HBT) effect is the foundation for stellar intensity interferometry. However, it is a phase insensitive two-photon interference effect. Here we extend the HBT interferometer by mixing intensity-matched reference fields with the input fields before intensity correlation measurement. With the freely available coherent state serving as the reference field, we experimentally demonstrate the phase sensitive two-photon interference effect when the input fields are thermal fields in either continuous wave or non-stationary pulsed wave and measure the complete complex second-order coherence function of the input fields without bringing them together from separate locations. Moreover, we discuss how to improve the signal level by using the more realistic continuous wave broadband anti-bunched light fields as the reference field. Our investigations pave the way for developing new technology of remote sensing and interferometric imaging with applications in long baseline high-resolution astronomy.