Heralded single-photon sources (HSPS) are widely used in experimental quantum science because they have negligibly small jitter and can therefore achieve high visibility for quantum interference. However, it is necessary to decrease the photon generation rate to suppress multi-photon components. To address this problem, two methods have been proposed and discussed: spatial (or temporal) source multiplexing and photon-pair number discrimination. Here, we report the experimental realization of a HSPS combining these two methods that can suppress the two-photon probability to 44.2 ± 0.7% of that of a normal HSPS. We also provide a theoretical analysis and a discussion of the effect of combining the two methods, considering a detector cascade as a practical photon number discriminating detector. The experimental results agreed well with the theoretical predictions.
Heralded single-photon sources (HSPS) are widely used in experimental quantum science because they have negligibly small jitter and can therefore achieve high visibility for quantum interference. However, it is necessary to decrease the photon generation rate to suppress multi-photon components. To address this problem, two methods have been proposed and discussed: spatial (or temporal) source multiplexing and photon-pair number discrimination. Here, we report the experimental realization of a HSPS combining these two methods that can suppress the two-photon probability to 44.2 ± 0.7% of that of a normal HSPS. We also provide a theoretical analysis and a discussion of the effect of combining the two methods, considering a detector cascade as a practical photon number discriminating detector. The experimental results agreed well with the theoretical predictions.
Summary form only given. Heralded single-photon sources (HSPS) are widely used in experimental quantum science because they have negligibly small jitter and can therefore achieve high visibility for quantum interference. However, it is necessary to decrease the photon generation rate to suppress multi-photon components. To address this problem, two methods have been proposed and discussed: spatial (or temporal) source multiplexing [1, 2] and photon-pair number discrimination [3]. Here, we report the first experimental realization of a HSPS combining these two methods that can suppress the two-photon probability to 44.2 ± 0.7% of that of a normal HSPS [4]. We also provide a theoretical analysis and a discussion of the effect of combining the two methods, considering a detector cascade as a practical photon number discriminating detector. The experimental results agreed well with the theoretical predictions.
Heralded single photon sources (HSPS) using spontaneous parametric down conversion (SPDC) are widely used in photonic quantum information. However, the excess-photon pair generation in SPDC process is a problem, which results in the events where more than two photons exist in a pulse. Such excess photons degrade the visibility (V) of two-photon Hong-Ou-Mandel interference, and are one of the main error causes in the advanced linear optics photonic circuits. Recently, we have developed a novel HSPS which combines two methods to suppress such excess photon numbers. The first method (A) is to use multiple SPDC sources in one HSPS, where upon the detection of the idler photon from one of the source, the corresponding signal photon is output. The second method (B) is to use cascaded detectors to monitor the photon-pair number generated from the source, where the detector distinguish the single-pair generation from multi-pair generation and thus the excess-photon generation can be suppressed. In this presentation, we report the theoretical calculations how such a source can improve the visibility for a two photon interference. For example, when the average number of pairs from SPDC in a pulse is 0.1, and the detection efficiency is 70%, V= 83.2% for a conventional HSPS. V is improved to 90.3%, 87.1% and 92.7% by using method A, B and our hybrid approach, respectively.
Abstract Heralded single-photon sources (HSPS) intrinsically suffer from multiphoton emission, leading to a trade-off between the source’s single-photon quality and the heralding rate. A solution to this problem is to use photon-number-resolving (PNR) detectors to filter out the heralding events where more than one photon pair is created. Here, we demonstrate an improvement of a HSPS by heralding photons using a high-efficiency parallel superconducting nanowire single-photon detector (P-SNSPD) with PNR power. Specifically, we show a reduction in the g ( 2 ) ( 0 ) of the heralded single photon by ( 26.9 ± 0.1 ) % for a fixed pump power, or alternatively, an increase in the heralding rate by a factor of 1.368 ± 0.002 for a fixed g ( 2 ) ( 0 ) . We also demonstrate that such a PNR device can reveal thermal photon-number statistics of unheralded photons, which is enabled by our ability to construct its full input–output response function. These results are possible thanks to our P-SNSPD architecture that ensures non-latching operation with no electrical crosstalk, which are essential conditions necessary to obtain the correct photon-number statistics and also faster recovery times, therefore enabling fast heralding rates. These results show that our efficient PNR P-SNSPD architecture can significantly improve the performance of HSPSs and can precisely characterize them, making these detectors a useful tool for a wide range of optical quantum information protocols.
Heralded single-photon sources (HSPS) intrinsically suffer from multiphoton emission, leading to a trade-off between the source's quality and the heralding rate. A solution to this problem is to use photon-number-resolving (PNR) detectors to filter out the heralding events where more than one photon pair is created. Here, we demonstrate the use of a high-efficiency PNR superconducting nanowire single-photon detector (SNSPD) as a heralding detector for a HSPS. By filtering out higher-order heralding detections, we can reduce the g(2)(0) of the heralded single photon by (26.6±0.2)%, or alternatively, for a fixed pump power, increasing the heralding rate by a factor of 1.363±0.004 for a fixed g(2)(0). Additionally, we use the detector to directly measure the photon-number distribution of a thermal mode and calculate the unheralded g(2)(0). We show the possibility to perform g(2)(0) measurements with only one PNR detector, with the results in agreement with those obtained by more common-place techniques which use multiple threshold detectors. Our work shows that efficient PNR SNSPDs can significantly improve the performance of HSPSs and can precisely characterize them, making these detectors a useful tool for a wide range of optical quantum information protocols.
Scalable quantum photonic technologies require the simultaneous production of highly indistinguishable multi-photon states with high probability. This need may be met, and the output probability significantly increased by multiplexed sources, which channel numerous low-probability heralded single-photon sources into a specified output mode using time or spatial multiplexing. However, conventional methods merely replicate these multiplexing units when scaled to multiple output modes, which is fundamentally inefficient because it discards many valid multi-photon events. To address this, we propose and experimentally demonstrate a novel multiplexing source architecture based on a multi-input/multi-output switching network, which can utilize combinatorial photon events. A super-exponential enhancement in multi-port single-photon creation is revealed by theoretical analysis, which significantly reduces the number of heralded single-photon sources needed. We demonstrate multiplexing with two output ports, supported by four integrated heralded single-photon sources. Our strategy has a generation probability of 1.60 times that of conventional methods and 2.58 times that of implementations without multiplexing. This multi-port multiplexed method opens a new avenue for establishing a solid foundation for advanced multi-photon quantum interference and large-scale quantum information processing.
Interference between single photons lies at the heart of linear optical quantum computing (LOQC). However, the lack of deterministic single photon sources hinders the large-scale experimental demonstration and its practical applications, as the probability to generate N single photons simultaneously (denoted by N-photon hereafter) decreases exponentially with the increasing number of single photon sources [1]. Multiplexing is the leading proposal to overcome this challenge by relocating single photon from different modes to one fixed mode. The theoretical work [2] indicates that the relative time multiplexing (RMUX) scheme could significantly enhance this probability and meanwhile reduce the requirements of multiplexing system, such as switching speed and system complexity. In this paper, RMUX of two heralded single photon sources is demonstrated for the first time. We observe around 90% enhancement on the heralded photon pair rate, compared to the standard time multiplexing (SMUX) scheme [3].