Abstract Fiber-based optical Kerr gating is a promising technique for ultrafast single-photon detection. While a fundamental trade-off between temporal resolution and detection efficiency has been anticipated, its experimental verification has remained elusive due to the lack of a suitable platform. In this study, we demonstrate the unexplored trade-off relationship using a highly efficient optical Kerr-gating system based on a photonic crystal fiber. Our results elucidate the inherent constraints governing the trade-off, providing a critical foundation for the future design and optimization of ultrafast single-photon detection.
Abstract Fiber-based optical Kerr gating is a promising technique for ultrafast single-photon detection. While a fundamental trade-off between temporal resolution and detection efficiency has been anticipated, its experimental verification has remained elusive due to the lack of a suitable platform. In this study, we demonstrate the unexplored trade-off relationship using a highly efficient optical Kerr-gating system based on a photonic crystal fiber. Our results elucidate the inherent constraints governing the trade-off, providing a critical foundation for the future design and optimization of ultrafast single-photon detection.
Ultrafast quantum optics with time-frequency entangled photons is at the forefront of progress towards future quantum technologies. However, to unravel the time domain structure of entangled photons and exploit fully their rich dimensionality, a single-photon detector with sub-picosecond temporal resolution is required. Here, we present ultrafast single-photon detection using an optical Kerr gate composed of a photonic crystal fiber (PCF) placed inside a Sagnac interferometer. A near-rectangle temporal waveform of a heralded single-photon generated via spontaneous parametric down-conversion is measured with temporal resolution as high as 224 ± 9 fs. The large nonlinearity and long effective interaction length of the PCF enables maximum detection efficiency to be achieved with only 30.5 mW gating pulse average power, demonstrating an order-of-magnitude improvement compared to optical gating with sum-frequency generation. Also, we discuss the trade-off relationship between detection efficiency and temporal resolution.
High temporal resolution detection for time-correlated single-photon counting (TCSPC) is critical for a broad range of applications, such as sensing, bio-imaging and quantum information. To harness non-classical advantages, high temporal resolution TCSPC is necessary to capture the unique properties of quantum entanglement, in which the precise time delays between two photons are used to reconstruct the biphoton distribution. However, current state-of-the art, high-resolution TCSPC systems, such as superconducting nanowires, have large footprints and require cryogenic cooling to liquid helium temperatures. They are not well equipped to be conveniently mounted on a satellite or transported within a health care facility. Small footprint, simple, low energy consuming single photon detection systems are therefore needed in order for high temporal resolution TCSPC applications to move beyond the research laboratory. In this direction, we demonstrate a proof-of-concept experiment for improving the temporal resolution of single-photon and biphoton detection schemes that is simple, fiber-based, and readily chip integrable. The principle relies on electrooptic gating of fast single-photon and biphoton signals using a high-speed RF pulse which drives an electro optic intensity modulator. As such, the instrument response function (IRF) of the detection scheme takes on the temporal profile of the electro-optic gate. Experimentally, we improve the IRF of our detection scheme from ~1.54 ns to <100 ps, allowing high resolution detection of ultrafast single photon TCSPC signals as well as to observe nonlocal dispersion cancellation effects in ultrafast biphoton distributions. This technique could allow for practical and simplified access to rapid temporal dynamics at the single photon scale.
The ultrafast detection of single photons is currently restricted by the limited time resolution (a few picoseconds) of the available single-photon detectors. Optical gates offer a faster time resolution, but so far they have been applied mostly to ensembles of emitters. Here, we demonstrate through a semi-analytical model that the ultrafast time-resolved detection of single quantum emitters can be possible using an optical Kerr shutter at gigahertz rates under focused illumination. This technique provides sub-picosecond time resolution, while keeping a gate efficiency at around 85%. These findings lay the ground for future experimental investigations on the ultrafast dynamics of single quantum emitters, with implications for quantum nanophotonics and molecular physics.
Advancements in the field of compact quantum photonics have enabled researchers to reliably generate and detect spectral and temporal correlated biphotons, opening avenues for diverse applications in quantum technology. Although many routine quantum interferometry and entanglement generation experiments are performed worldwide, only a few studies discuss how different experimental detection and correlation measurement parameters can significantly influence the raw outcomes of these experiments. In this work, we analytically and experimentally elucidate the impact of quantum efficiency and dead time of single-photon detectors, and bin width of the time correlator on the coincidence-to-accidental ratio (CAR) and hence the quantum temporal cross-correlations (gsi2(0)) of photon pairs generated at 1560 nm via a type-II MgO:ppLN ridge waveguide-based source. We experimentally achieved a high cross-correlation of up togsi2(0)=∼104at different detection settings, thus revealing the high-quality of photon-pair correlations, surpassing several state-of-the-art biphoton sources. Additionally, we demonstrate how this analysis anticipates the effect of afterpulsing, temporal distinguishability between signal and idler photons, and temporal resolution of the correlation analysis. We further use this analysis for application in Hong-Ou-Mandel (HOM) interferometry and achieve raw visibility∼99±1%. To the best of our knowledge, such high raw HOM visibility has not been previously reported in a fiber-based type-II SPDC configuration. This study is important for understanding the quantum source and finding the optimal detection settings to operate it on for its real-time practical implementation in various quantum optical experiments.
The generation and efficient detection of ultrafast single photons is at the forefront of modern optical science, and it offers an unprecedented set of capabilities, for instance, in the area of quantum information science, high-sensitivity detection, and remote sensing [1] - [3] . In addition, it provides a powerful analysis tool in the life sciences at the single-molecule level [4] . The detection of single photons is currently restricted by the limited time resolution (a few picoseconds) of the available single-photon detectors.
Single photons are a natural platform for quantum technologies as they support entanglement in many degrees of freedom and are inherently well protected from a detrimental type of noise called decoherence. In order to fully exploit photons for quantum technologies, it will be necessary to be able to shape, control, and measure their properties in all degrees of freedom: space, time, frequency, and polarization. \n \n The time-frequency degree of freedom of light is of particular interest for quantum information tasks as it supports various encodings, including frequency bins and time bins, and is intrinsically robust for propagation through long-distance fibre links. Applications which harness quantum correlations in this degree of freedom, referred to as energy-time entanglement, include dispersion cancellation and high-dimensional quantum key distribution. However, detection of this entanglement and observation of these effects requires time resolution beyond the capabilities of current photon detectors. Thus, for operations on ultrafast time scales, more powerful and complex methods are required. \n \n In this thesis, we use a nonlinear technique known as optical gating to surpass the limitations in current detectors and measure single photon pairs, improving the time resolution by two orders of magnitude. When a single photon enters a nonlinear medium at the same time as a strong laser pulse, it may upconvert to a higher energy photon. The strong laser pulse effectively acts as an ultrafast shutter or gate and this creates a high resolution snapshot of the photon in time. Optical gating in conjunction with single photon spectrometers then allow us to measure both the spectral and temporal features of photons on subpicosecond time scales. \n \n These high resolution measurements enable us to explore a host of quantum effects which remained previously inaccessible. First, we directly observe energy-time entanglement, analogous to Einstein-Rosen-Podolsky correlations but \\emph{in frequency and time}. Then, with full control over the dispersion of each photon, we observe nonlocal dispersion cancellation on femtosecond time scales. We also explore ultrafast interferometry in the quantum domain by temporally resolving two-photon interference from a Franson interferometer and observe a violation of the CHSH-Bell inequality. Finally, we show that, using these measurements, it is possible to reconstruct a two-photon energy-time entangled state. Such measurement capabilities will be essential to precisely control both the spectral and temporal shape of entangled photons and to develop new applications in quantum state engineering.