Recent active development of quantum computers and quantum key distribution systems requires characterization of the parameters of single-photon detectors. A key parameter of single-photon detectors is detection efficiency. One of the methods for measuring the detection efficiency given in the international ETSI standard is the Klyshko reference-free method based on the use of the effect of spontaneous parametric downconversion. The signal-to-noise ratio (SNR) of this method depends on a combination of the pump wavelength, the nonlinear crystal axis angle, and the type of detector sensitive element. When the combination is complex, one has to deal with low SNR. In this case, to obtain a high SNR, long-term signal accumulation is necessary. In real detectors, the situation is complicated by the presence of a high noise level at low frequencies. The heterodyning-based method we have proposed consists in introducing modulation into the standard Klyshko scheme and accumulating the signal at a higher frequency. The method was numerically modeled and experimentally tested. A 14 times improvement in SNR was demonstrated compared to simple signal accumulation.
Recent active development of quantum computers and quantum key distribution systems requires characterization of the parameters of single-photon detectors. A key parameter of single-photon detectors is detection efficiency. One of the methods for measuring the detection efficiency given in the international ETSI standard is the Klyshko reference-free method based on the use of the effect of spontaneous parametric downconversion. The signal-to-noise ratio (SNR) of this method depends on a combination of the pump wavelength, the nonlinear crystal axis angle, and the type of detector sensitive element. When the combination is complex, one has to deal with low SNR. In this case, to obtain a high SNR, long-term signal accumulation is necessary. In real detectors, the situation is complicated by the presence of a high noise level at low frequencies. The heterodyning-based method we have proposed consists in introducing modulation into the standard Klyshko scheme and accumulating the signal at a higher frequency. The method was numerically modeled and experimentally tested. A 14 times improvement in SNR was demonstrated compared to simple signal accumulation.
Active development of quantum informational components such as quantum computers and quantum key distribution systems requires parameter characterization of single photon detectors. A key property of the single photon detectors is detection efficiency. One of the methods of the detection efficiency measurement, as listed in the international standard ETSI, is the reference-free twin-photon-based Klyshko method. The signal-to-noise ratio (SNR) of this method depends on the combination of the pump wavelength, the nonlinear crystal's axis angle, and the type of detector's sensitive element. When the combination is difficult, one has to deal with the low SNR of the detector counts measurement. To gain the high SNR, one has to average the long record complicated with the "random telegraph signal" noise. This type of noise exhibits high spectral density at a zero frequency, where simple averaging works. The heterodyne based method we have proposed is to perform averaging at the higher frequency of the modulation introduced to the standard Klyshko measurement scheme. The method was numerically simulated and experimentally tested. The 14 times improvement in SNR for the proposed method relative to the simple averaging was demonstrated by the numerical simulation and confirmed experimentally.
InGaAs/InP single-photon detectors are today the most frequently used detectors for fibre-based Quantum Key Distribution (QKD) [1,2]. The performance of the QKD-systems greatly depends on the optical properties of its detector, such as quantum efficiency, dead time, dark counts, gating rate, etc., which need to be metrologically characterized to fully grantee the QKD network security. Therefore, several European National Metrological Institutes (NMIs) are putting today great efforts in developing novel measurement methods and calibration facilities, which allow to perform the traceable characterisation of single-photon detectors by using reference standards [3, 4]. From the metrological, and specifically radiometric, point of view, the detection efficiency of the single-photon detector is the main parameter that needs to be traceable to the primary standard for optical power (i.e. the cryogenic radiometer), which is maintained by most of the NMIs. Recently, four European NMIs have carried out a pilot comparison on the detection efficiency of a free-running InGaAs/InP single-photon detector, which main purpose has been to provide a snapshot of the measurement capabilities of the four European NMIs in the field of photon counting detection. The comparison was carried out in the framework of the EMPIR project 14IND05 “Optical metrology for quantum-enhanced secure telecommunication (MIQC2)” at the telecom wavelength of 1550 nm by using different reference standards with independently traceability chains. The results of this comparison, including the different experimental setups, the measurement methods, the traceability chain and the uncertainty evaluation of each participant, will be presented in this conference. References: [1] Akihisa Tomita, et al., “High speed quantum key distribution system”, Optical Fiber Technology, 16, Issue 1, 55-62 (2010). [2] Damien Stucki, et al., “Photon counting for quantum key distribution with peltier cooled InGaAs/InP APDs”, Journal of Modern Optics, 48, Issue 13, 1967-1981 (2001). [3] M. López, et al, “Detection efficiency calibration of single-photon silicon avalanche photodiodes traceable using double attenuator technique, Journal of Modern Optics 62, S21 – S27, 2015. [4] G. Porrovecchio, et al., “Comparison at the sub-100 fW optical power level of calibrating a single-photon detector using a high-sensitive, low-noise silicon photodiode and the double attenuator technique”, Metrologia 53, 1115-1122 (2016).
Single-photon detectors are of great importance in spectroscopy, laser ranging, astronomy and wherever weak light detection is required, so a precise knowledge of their quantum efficiency is essential, but their calibration is by no means trivial. Traditional methods need a black body radiation source or a highly attenuated laser beam as a reference standard, or an already calibrated reference detector. It is well known that absolute measurement of the quantum efficiency, absolute in the sense that the calibration is independent of any radiometric standard or the properties of another detector, can be performed using entangled twin photons generated in optical spontaneous parametric down-conversion together with a reference detector. We have performed the first proof-of-principle experiment to determine the quantum efficiency by which no second detector or reference standard is required. This absolute self-calibration method is also based on the time correlation of photons emitted in parametric down-conversion, but with the introduction of a suitable time delay between the arrival times of the twin photons. Furthermore, we describe a scheme for absolute self-calibration of the quantum efficiency at different wavelengths by means of a pulsed source of nondegenerate down-converted photons. This method should have even greater potential for applications.
We developed low-noise up-conversion single photon detectors for 1310 nm based on a periodically-poled LiNbO3 (PPLN) waveguide. The low-noise feature is achieved by using a pulsed optical pump at a wavelength longer than the signal wavelength. The detectors were used in a quantum key distribution (QKD) systems based on polarization encoding, measurement for entangled photon pairs and spectrum measurement at single photon levels. In this paper, the overall detection efficiency and noise level of the detectors are characterized and the polarization and wavelength sensitivity of the detection efficiency is analyzed. The applications of this detector in quantum information systems are also described.
Single-photon detectors are of great importance in spectroscopy, laser ranging, astronomy and wherever weak light detection is required, so a precise knowledge of their quantum efficiency is essential, but their calibration is by no means trivial. Traditional methods need a black body radiation source or a highly attenuated laser beam as a reference standard, or an already calibrated reference detector. It is well known that absolute measurement of the quantum efficiency, absolute in the sense that the calibration is independent of any radiometric standard or the properties of another detector, can be performed using entangled twin photons generated in optical spontaneous parametric down-conversion together with a reference detector. We have performed the first proof-of-principle experiment to determine the quantum efficiency by which no second detector or reference standard is required. This absolute self-calibration method is also based on the time correlation of photons emitted in parametric down-conversion, but with the introduction of a suitable time delay between the arrival times of the twin photons. Furthermore, we describe a scheme for absolute self-calibration of the quantum efficiency at different wavelengths by means of a pulsed source of nondegenerate down-converted photons. This method should have even greater potential for applications.
We demonstrate niobium nitride based superconducting single-photon detectors sensitive in the spectral range 452–2300 nm. The system performance was tested in a real-life experiment with correlated photons generated by means of spontaneous parametric downconversion, where one photon was in the visible range and the other was in the infrared range. We measured a signal to noise ratio as high as 4×104 in our detection setting. A photon detection efficiency as high as 64% at 1550 nm and 15% at 2300 nm was observed.