Spatial correlations between two photons are the key resource in realising many quantum imaging schemes. Measurement of the bi-photon correlation map is typically performed using single-point scanning detectors or single-photon cameras based on CCD technology. However, both approaches are limited in speed due to the slow scanning and the low frame-rate of CCD-based cameras, resulting in data acquisition times on the order of many hours. Here we employ a high frame rate, single photon avalanche diode (SPAD) camera, to measure the spatial joint probability distribution of a bi-photon state produced by spontaneous parametric down-conversion, with statistics taken over $10^7$ frames acquired in just 140 seconds. We verified the presence of spatial entanglement between our photon pairs through the violation of an Einstein-Podolsky-Rosen criterion, with a confidence level of 227 sigmas. Our work demonstrates the potential of SPAD cameras in the rapid characterisation of photon correlations, leading the way towards quantum imaging in real-time.
We experimentally demonstrate optical control of negative-feedback avalanche diode (NFAD) detectors using bright light. We deterministically generate fake single-photon detections with a better timing precision than normal operation. This could potentially open a security loophole in quantum cryptography systems. We then show how monitoring the photocurrent through the avalanche photodiode can be used to reveal the detector is being blinded.
This paper describes the design, fabrication, and performance of planar-geometry InGaAs-InP devices which were specifically developed for single-photon detection at a wavelength of 1550 nm. General performance issues such as dark count rate, single-photon detection efficiency, afterpulsing, and jitter are described.
We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23 GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating sys…
We have performed a detailed study of the dependence of afterpulse probability in InGaAs/InP sine-gated SPAD on the dead time and the existing approach for its implementation. We demonstrated an electrical scheme combining sinusoidal gating and active reset. We have shown when such solutions are beneficial from the key distribution point of view and enough to use a simple scheme with a snatching comparator. We have also proposed a precise method for measuring the afterpulse and presented a model describing the non-markovian dynamic of this effect. We have demonstrated that our afterpulsing mea…
Single-shot high-resolution spectroscopy of single-photon-level optical pulses using a virtually imaged phased-array and single-photon avalanche diode array
Single-photon-avalanche diode (SPAD) arrays are essential tools in biophotonics, optical ranging and sensing and quantum optics. However, their small number of pixels, low quantum efficiency and small fill factor have so far hindered their use for practical imaging applications. Here, we demonstrate full-field entangled photon pair correlation imaging using a 100-kpixels SPAD camera. By measuring photon coincidences between more than 500 million pairs of positions, we retrieve the full point spread function of the imaging system and subsequently high-resolution images of target objects illumin…
We characterize a new commercial, back-illuminated reach-through silicon single-photon avalanche photo diode (SPAD) SAP500 (Laser Components. Inc.), operated in Geiger-mode for purpose of photon counting. We show that for this sensor a significant interplay exists between dark counts, detection efficiency, afterpulsing, excess voltage and operating temperature, sometimes requiring a careful optimization tailored for a specific application. We find that a large flat plateau of sensitive area of about 0.5 mm in diameter, a peak quantum efficiency of 73% at 560 nm and timing precision down to 150…
Temporal photon correlation measurement, instrumental to probing the quantum properties of light, typically requires multiple single photon detectors. Progress in single photon avalanche diode (SPAD) array technology highlights their potential as high performance detector arrays for quantum imaging and photon number resolving (PNR) experiments. Here, we demonstrate this potential by incorporating a novel on-chip SPAD array with 55% peak photon detection probability, low dark count rate and crosstalk probability of 0.14% per detection, in a confocal microscope. This enables reliable measurement…
InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization. The parameters of photon detection ef…
Silicon single-photon avalanche diode (SPAD) is a core device for single-photon detection in the visible and the near-infrared range, and widely used in many applications. However, due to limits of the structure design and device fabrication for current silicon SPADs, the key parameters of detection befficiency and timing jitter are often forced to compromise. Here, we propose a nanostructured silicon SPAD, which achieves high detection efficiency with excellent timing jitter simultaneously over a broad spectral range. The optical and electric simulations show significant performance enhanceme…
Single-photon detectors are a pivotal component in photonic quantum technologies. A precise and comprehensive calibration of the intrinsic detection efficiency is of utmost importance to ensure the proper evaluation of the performance in view of the specific technological application of interest, such as the protection against security breaches in quantum cryptographic solutions. Here we report on a systematic study on and comprehensive analysis of the estimation of the intrinsic detection efficiency of two commercial single-photon detectors based on single-photon avalanche diodes (SPADs) for …
Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers…
We report on the first demonstration of fluorescence detection using single-photon avalanche photodiodes (SPADs) monolithically integrated with a microfabricated surface ion trap. The SPADs are positioned below the trapping positions of the ions, and designed to detect 370 nm photons emitted from single $^{174}$Yb$^+$ and $^{171}$Yb$^+$ ions. We achieve an ion/no-ion detection fidelity for $^{174}$Yb$^+$ of 0.99 with an average detection window of 7.7(1) ms. We report a dark count rate as low as 1.2 kHz at room temperature operation. The fidelity is limited by laser scatter, dark counts, and h…
A near-infrared (NIR) enhanced silicon single-photon avalanche diode (SPAD) fabricated in a customized 0.13 $μ$m CMOS technology is presented. The SPAD has a depleted absorption volume of approximately 15 $μ$m x 15 $μ$m x 18 $μ$m. Electrons generated in the absorption region are efficiently transported by drift to a central active avalanche region with a diameter of 2 $μ$m. At the operating voltage, the active region contains a spherically uniform field peak, enabling the multiplication of electrons originating from all corners of the device. The advantages of the SPAD architecture include hig…
We have performed a statistical characterization of the effect of afterpulsing in a free-running silicon single-photon detector by measuring the distribution of afterpulse waiting times in response to pulsed illumination and fitting it by a sum of exponentials. We show that a high degree of goodness of fit can be obtained for 5 exponentials, but the physical meaning of estimated characteristic times is dubious. We show that a continuous limit of the sum of exponentials with a uniform density between the limiting times gives excellent fitting results in the full range of the detector response f…
Photonic quantum technologies promise a revolution of the world of information processing, from simulation and computing to communication and sensing, thanks to the many advantages of exploiting single photons as quantum information carriers. In this scenario, single-photon detectors play a key role. On the one hand, superconducting nanowire single-photon detectors (SNSPDs) are able to provide remarkable performance on a broad spectral range, but their applicability is often limited by the need of cryogenic operating temperatures. On the other hand, single-photon avalanche diodes (SPADs) overc…
We report on the first realization of time-dependent quantum detector tomography for commercially available InGaAs avalanche photo detectors. For the construction of appropriate time-dependent POVMs from experimentally measured data, we introduce a novel scheme to calculate the weight of the regularization term based on the amount of measured data. We compare our POVM-based results with the theoretical predictions of the previously developed model by Gouzien et al. In contrast to our measurement-based construction of a time-dependent POVM for photon detectors, this previous investigation exten…
Single-photon detectors, like Avalanche Photo Diodes (APDs), have a great importance in many fields like quantum key distribution, laser ranging, florescence microscopy, etc. Afterpulsing is a typical non ideal behavior of APDs, operated in Geiger mode, which adversely affects any application which measures the number or timing of detection events. Several conflicting studies have tried to model afterpulsing behavior and link it to fundamental semiconductor physics. Here we describe experiments we performed on at least 2 different detectors from 3 manufacturers, all commonly used in quantum op…
Previously, we built up a set of photon-free quantum random number generator(QRNG) with InGaAs single photon avalanche diodes. We exploited the stochastic property of quantum tunneling effect. Here, we utilized tunneling signals in Si diodes to implement quantum random number generator. In our experiment, instead of applying periodic pulses between the diode as we did in the InGaAs QRNG, we applied fixed voltage and detect time intervals between adjacent tunneling signals, as random source. This Si QRNG has a high performance in the randomness of its raw data and almost post-processing-free. F…
It is challenging to implement genuine free running single photon detectors for the 1550 nm wavelength range with simultaneously high detection efficiency (DE), low dark noise, and good time resolution. We report a novel read out system for the signals from a negative feedback avalanche diode (NFAD) which allows useful operation of these devices at a temperature of 193 K and results in very low dark counts (~100 CPS), good time jitter (~30 ps), and good DE (~10%). We characterized two NFADs with a time correlation method using photons generated from weak coherent pulses (WCP) and photon pairs …
Single-photon detectors (SPDs) are the most sensitive instruments for light detection. In the near-infrared range, SPDs based on III-V compound semiconductor avalanche photodiodes have been extensively used during the past two decades for diverse applications due to their advantages in practicality including small size, low cost and easy operation. In the past decade, the rapid developments and increasing demands in quantum information science have served as key drivers to improve the device performance of single-photon avalanche diodes and to invent new avalanche quenching techniques. This Re…
Here we report and discuss the avalanche-like up-conversion behavior in absence of the avalanche. We experimentally observed significant changes in the slope of the curve for the intensity dependence of up-conversion luminescence of erbium ions in green band on the pump intensity of the diode laser. Such changes are typical for the photon avalanche. However, the concentration of erbium ions is insufficient for an efficient exchange of energy between them, and excitation of a photon avalanche is not possible. Using a simple three-level approximation of the up-conversion process model, we have s…
In this work we investigate operation in the Geiger mode of the new single photon avalanche photo diode (SPAD) SAP500 manufactured by Laser Components. This SPAD is sensitive in the range 400-1000nm and has a conventional reach-through structure which ensures good quantum efficiency at the long end of the spectrum. By use of passive and active quenching schemes we investigate detection efficiency, timing jitter, dark counts, afterpulsing, gain and other important parameters and compare them to the "standard" low noise SPAD C30902SH from Perkin Elmer. We conclude that SAP500 offers better combi…
InGaAs/InP-based semiconductor avalanche photodiode are usually employed for single-photon counting at telecom wavelength. However they are affected by afterpulsing which limits the diode performance. Recently, Princeton Lightwave has commercialised a diode integrating monolithically a feedback resistor. This solution effectively quenches the avalanche and drastically reduces afterpulsing. Here, we report the development and characterization of a detector module based on this diode, implementing an active hold-off circuit which further reduces the afterpulsing and notably improves the detector…
Single photon avalanche diodes (SPADs) are the most commercially diffused solution for single-photon counting in quantum key distribution (QKD) applications. However, the secondary photon emission, arising from the avalanche of charge carriers during a photon detection, may be exploited by an eavesdropper to gain information without forcing errors in the transmission key. In this paper, we characterise such backflash light in gated InGaAs/InP SPADs, and its spectral and temporal characterization for different detector models and different operating parameters. We qualitatively bound the maximu…
We report a 1.036 GHz gated Geiger mode InGaAs avalanche photodiode with a detection dead time of just 1.93 ns. This is demonstrated by full recovery of the detection efficiency two gate cycles after a detection event, as well as a measured maximum detection rate of 497 MHz. As an application, we measure the second order correlation function $g^{(2)}$ of the emission from a diode laser with a single detector which works reliably at high speed owing to the extremely short dead time of the detector. The device is ideal for high bit rate fiber wavelength quantum key distribution and photonic quan…
In this work we investigate the probabilities of detecting single- and multi-photon coherent states on InGaAs/InP sine-gated and free-run single-photon avalanche diodes. As a result, we conclude that multi-photon state detection cannot be regarded as independent events of absorption of individual single-photon states. However, if a greater number of states are one- and two-photon, then an Independent model is permissible. We conclude that physical processes must occur in the diode structure, determining the correlation when several photons are absorbed simultaneously. We present two models tha…
A photon detector combining the two avalanche photon diodes (APD) has been demonstrated for qubit discrimination in 1550 nm. Spikes accompanied with the signals in gated-mode were canceled by balanced output from the two APDs. The spike cancellation enabled one to reduce the threshold in the discriminators, and thus the gate pulse voltage. The dark count probability and afterpulse probability were reduced to 7x10^-7 and 10^-4, respectively, without affecting the detection efficiency (11 %) at 178 K.
Single photon detectors are important for a wide range of applications each with their own specific requirements, which makes necessary the precise characterization of detectors. Here, we present a simple and accurate methodology of characterizing dark count rate, detection efficiency, and after-pulsing in single photon detectors purely based on their counting statistics. We demonstrate our new method on a custom-made, free-running single photon detector based on an InGaAs based avalanche photo diode (APD), though the methodology presented here is applicable for any type of single photon detec…
We demonstrate the importance and utility of Monte Carlo simulation of single-photon detectors. Devising an optimal simulation is strongly influenced by the particular application because of the complexity of modern, avalanche-diode-based single-photon detectors.. Using a simple yet very demanding example of random number generation via detection of Poissonian photons exiting a beam splitter, we present a Monte Carlo simulation that faithfully reproduces the serial autocorrelation of random bits as a function of detection frequency over four orders of magnitude of the incident photon flux. We …
We demonstrate a picosecond source of correlated photon pairs using a micro-structured fibre with zero dispersion around 715 nm wavelength. The fibre is pumped in the normal dispersion regime at ~708 nm and phase matching is satisfied for widely spaced parametric wavelengths. Here we generate up to 10^7 photon pairs per second in the fibre at wavelengths of 587 nm and 897 nm. On collecting the light in single-mode-fibre-coupled Silicon avalanche diode photon counting detectors we detect ~3.2.10^5 coincidences per second at pump power 0.5 mW.
Integrated quantum photonics, which allows for the development and implementation of chip-scale devices, is recognized as a key enabling technology on the road towards scalable quantum networking schemes. However, many state-of-the-art integrated quantum photonics demonstrations still require the coupling of light to external photodetectors. On-chip silicon single-photon avalanche diodes (SPADs) provide a viable solution as they can be seamlessly integrated with photonic components, and operated with high efficiencies and low dark counts at temperatures achievable with thermoelectric cooling. …
Single photon avalanche diode arrays can provide both the spatial and temporal information of each detected photon. We present here the characterization of entangled light with a sensor specifically designed for quantum imaging applications. The sensors is time-tagging each detection events at the pixel level with sub-nanosecond accuracy, within frames of 50 ns. The spatial correlations between any number of detections in a defined temporal window can thus be directly extracted from the data. We show the ability of the sensor to characterize space-momentum entangled photon pairs emitted by spo…
We report on a novel device capable of imaging second-order spatio-temporal correlations g2(x,t) between photons. The imager is based on a monolithic array of single-photon avalanche diodes (SPAD) implemented in CMOS technology and a simple algorithm to treat multiphoton time-of-arrival distributions from different SPAD pairs. It is capable of 80 ps temporal resolution with fluxes as low as 10 photons/s at room temperature. An important application might be the local imaging of g2 as a means of confirming the presence of true Bose-Einstein macroscopic coherence (BEC) of cavity exciton polarito…
Photon-number measurements are a fundamental technique for the discrimination and characterization of quantum states of light. Beyond the abilities of state-of-the-art devices, we present measurements with an array of 100 avalanche photodiodes exposed to photon-numbers ranging from well below to significantly above one photon per diode. Despite each single diode only discriminating between zero and non-zero photon-numbers we are able to extract characteristic information about the quantum state. We demonstrate a vast enhancement of the applicable intensity range by two orders of magnitude rela…
Despite advances in low-light level detection, single-photon methods such as photon correlation have rarely been used in the context of imaging. The few demonstrations, for example of sub-diffraction limited imaging utilizing quantum statistics of photons, have remained in the realm of proof-of-principle demonstrations. This is primarily due to a combination of low values of fill factors, quantum efficiencies, frame rates and signal-to-noise characteristic of most available single-photon sensitive imaging detectors. Here we describe an imaging device based on a fiber bundle coupled to single-p…
Quantum techniques can be used to enhance the signal-to-noise ratio in optical imaging. Leveraging the latest advances in single photon avalanche diode array cameras and multi-photon detection techniques, here we introduce a super-sensitive phase imager, which uses space-polarization hyper-entanglement to operate over a large field-of-view without the need of scanning operation. We show quantum-enhanced imaging of birefringent and non-birefringent phase samples over large areas, with sensitivity improvements over equivalent classical measurements carried out with equal number of photons. The p…
We demonstrate a single-photon sensitive spectrometer in the visible range, which allows us to perform time-resolved and multi-photon spectral correlation measurements. It is based on a monochromator composed of two gratings, collimation optics and an array of single photon avalanche diodes. The time resolution can reach $110$ ps and the spectral resolution is $2$ nm/pixel, limited by the design of the monochromator. This technique can easily be combined with commercial monochromators, and can be useful for joint spectrum measurements of two photons emitted in the process of parametric down co…
Slow-light media are of interest in the context of quantum computing and enhanced measurement of quantum effects, with particular emphasis on using slow-light with single photons. We use light-in-flight imaging with a single photon avalanche diode camera-array to image in situ pulse propagation through a slow light medium consisting of heated rubidium vapour. Light-in-flight imaging of slow light propagation enables direct visualisation of a series of physical effects including simultaneous observation of spatial pulse compression and temporal pulse dispersion. Additionally, the single-photon …
InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 hours. The detector system can substantially enhance QKD perf…
The measurement of light characteristics at the single- and few photon level plays a key role in many quantum optics applications. Often photodetection is preceded with the transmission of quantum light over long distances in optical fibers with their low loss window near 1550nm. Nonetheless, the detection of the photonic states at telecommunication wavelengths via avalanche photodetectors has long been facing severe restrictions. Only recently, demonstrations of the first free-running detector techniques in the telecommunication band have lifted the demand of synchronizing the signal with the…
We measure the detection efficiency of single-photon detectors at wavelengths near 851 nm and 1533.6 nm. We investigate the spatial uniformity of one free-space-coupled single-photon avalanche diode and present a comparison between fusion-spliced and connectorized fiber-coupled single-photon detectors. We find that our expanded relative uncertainty for a single measurement of the detection efficiency is as low as 0.70 % for fiber-coupled measurements at 1533.6 nm and as high as 1.78 % for our free-space characterization at 851.7 nm. The detection-efficiency determination includes corrections f…
InGaAs/InP single-photon detectors (SPDs) are widely used for near-infrared photon counting in practical applications. Photon detection efficiency (PDE) is one of the most important parameters for SPD characterization, and therefore increasing PDE consistently plays a central role in both industrial development and academic research. Here we present the implementation of high-frequency gating InGaAs/InP SPD with a PDE as high as 60% at 1550 nm. On one hand, we optimize the structure design and device fabrication of InGaAs/InP single-photon avalanche diode with an additional dielectric-metal re…
