High Single-photon Detection Efficiency Research Articles

Ultra-low dark count rate and high system efficiency single-photon detectors with 50 nm-wide superconducting wires

Both system detection efficiency (DE) and dark count rate (DCR) are critical parameters of single-photon detectors for practical applications. For a superconducting nanowire single-photon detector (SNSPD), DE is always achieved with high bias current, which also produces high dark count rate. In this paper, we analyzed the DE of SNSPD with 50 nm NbN nanowires patterned on the films with a thickness of 4 and 6 nm. The maximum DE for communication wavelengths is 10.3% at 1310 nm with a 50 nm-wide and 4 nm-thick device. The chip with 6 nm thickness shows high DE at ultra-low dark count rate. For example, DEs of 32% for 404 nm photons and 21% for 660 nm photons were achieved at a low dark count rate of 0.01 Hz. Comparing with the SNSPD with 4 nm-thick films, the improved DE for visible photons with the 6 nm-thick SNSPD is caused by the increased absorbance of NbN films, which also reduced the dark count rate produced by thermal activation around film defects. By optimizing the micro-fabrication process and further decreasing the nanowire width while retaining uniformity, the wavelength response of the 6 nm-thick SNSPD may be extended to infrared photons.

Efficient entanglement distribution over 200 kilometers

Here we report the first demonstration of entanglement distribution over a record distance of 200 km which is of sufficient fidelity to realize secure communication. In contrast to previous entanglement distribution schemes, we use detection elements based on practical avalanche photodiodes (APDs) operating in a self-differencing mode. These APDs are low-cost, compact and easy to operate requiring only electrical cooling to achieve high single photon detection efficiency. The self-differencing APDs in combination with a reliable parametric down-conversion source demonstrate that entanglement distribution over ultra-long distances has become both possible and practical. Consequently the outlook is extremely promising for real world entanglement-based communication between distantly separated parties.

High-Detectivity and High-Single-Photon-Detection-Efficiency 4H-SiC Avalanche Photodiodes

We report large-area, 250-mum-diameter, 4H-SiC avalanche photodiodes with low dark current and high gain. At room temperature, the dark current density is 59.5 nA/cm2 at a gain of 1000. An external quantum efficiency of 48% at 280 nm is achieved at unity gain with a recessed-window structure. The differential resistance of the recessed-window device at zero bias is estimated to be 6times1014 Omega. As a result of high external quantum efficiency, large area, and large differential resistance, a record high specific detectivity of 4.1times1014 cmHz1/2 W-1, has been achieved. In Geiger mode operation, high single photon detection efficiency of 30% with dark count probability of 8times10-4 is reported.

Optical Quantum Computing

In 2001, all-optical quantum computing became feasible with the discovery that scalable quantum computing is possible using only single-photon sources, linear optical elements, and single-photon detectors. Although it was in principle scalable, the massive resource overhead made the scheme practically daunting. However, several simplifications were followed by proof-of-principle demonstrations, and recent approaches based on cluster states or error encoding have dramatically reduced this worrying resource overhead, making an all-optical architecture a serious contender for the ultimate goal of a large-scale quantum computer. Key challenges will be the realization of high-efficiency sources of indistinguishable single photons, low-loss, scalable optical circuits, high-efficiency single-photon detectors, and low-loss interfacing of these components.

Low Dark Count Rate and High Single-Photon Detection Efficiency Avalanche Photodiode in Geiger-Mode Operation

An In0.53Ga0.47As-InP avalanche photodiode with very low dark current (0.15 pA at 95% breakdown voltage, 200 K) has been characterized in gated mode for single-photon detection. The temperature dependence of dark current and dark count yields activation energy of ~0.4 eV from 240 K to 297 K. High single-photon detection efficiency (SPDE) at telecom wavelengths with very low dark count rate (DCR) (e.g., DCR =12 kHz at SPDE =45% at 1.31 mum and 200 K) was achieved

High-Performance InGaAs/InP Single-Photon Avalanche Photodiode

In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/InP avalanche photodiodes with very low dark current have been characterized in gated mode for single-photon detection. A 40-mum-diameter single-photon avalanche diodes (SPAD) exhibited high single-photon detection efficiency (SPDE = 45% at 1.31 mum), low dark count rate (DCR = 12 kHz), and low noise-equivalent power (NEP=4.5X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-17</sup> W/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> W/Hz) at 200 K and 1.31 mum. A timing resolution of 140 ps was achieved with an SPDE of 45%. In addition, the dark current and DCR of a 4X4 SPAD array are reported.

High-efficiency single-photon detectors.

Using correlated photon pairs produced via spontaneous parametric down-conversion, we have measured the absolute single-photon detection efficiencies and time responses of four detectors: two solid-state photomultipliers (SSPM's) manufactured by Rockwell International Corp., and two custom-modified single-photon counting modules (SSPM's) manufactured by EG, Canada. The highest observed efficiencies were 70.9\ifmmode\pm\else\textpm\fi{}1.9% (with an SSPM, at a wavelength of 632 nm) and 76.4\ifmmode\pm\else\textpm\fi{}2.3% (with an SPCM, at 702 nm). We believe these to be the highest reported single-photon detection efficiencies in the visible spectrum; they are important for quantum cryptography and loophole-free tests of Bell's inequalities, as well as more prosaic applications such as photon correlation spectroscopy and velocimetry. We found that the time profile for coincidences between the SSPM and the SPCM consisted of a main peak with a 3.5-ns full width at half maximum (FWHM) preceded by a smaller peak by 11 ns. A similar time profile between two SPCM's displayed only one peak, with a 300-ps FWHM. Afterpulses were detected in the SPCM's at a level of less than ${10}^{\mathrm{\ensuremath{-}}4}$ of the counting rate, with an exponential decay time constant of 4.5 \ensuremath{\mu}s.