Single-photon Communication Research Articles

Probability of Erroneous Data Registration in a Single Photon Erasure-Type Communication Channel with a Receiver Based on a Photon Counter

When measuring low-power optical signals, it is necessary to ensure the highest reliability of the received data, which is especially important for single-photon communication channels. This determines the expediency of using photon counters as receiving modules for such channels. They are highly sensitive, but are characterized by data recording errors. Therefore, the purpose of this work was to investigate the influence of the intensity of the registered optical radiation J0 during the transmission of binary symbols “0” on the probability of registering symbols “1” at the output of the communication channel in the presence of symbols “0” at its input P(1/0).The statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter during the registration of binary symbols “0” Pst0 (N ) were determined. To do this, a technique was used to reduce information loss. As a result, the minimum probability P(1/0) was reached.The probabilities P(1/0) were calculated for a communication channel containing a photon counter as a receiving module. This calculation was carried out at different values of the supply voltage of the avalanche photodetector U and the intensity of the optical signal used to transmit the binary symbols “0” J0 .The experimental results showed that with increasing optical signal intensity J0 , the dependences P(1/0) on J0 initially remain almost unchanged and retain a constant value. However, with a further increase in J0 , there is a linearly increasing character of the dependences P(1/0) on J0 . Moreover, with other equal reception parameters, such a character of the dependences P(1/0) on J0 begins to manifest itself at higher intensities of the optical signal J0 with an increase in the supply voltage of the avalanche photodetector.

Proximal nitrogen reduces the fluorescence quantum yield of nitrogen-vacancy centres in diamond

The nitrogen-vacancy colour centre in diamond is emerging as one of the most important solid-state quantum systems. It has applications to fields including high-precision sensing, quantum computing, single photon communication, metrology, nanoscale magnetic imaging and biosensing. For all of these applications, a high quantum yield of emitted photons is desirable. However, diamond samples engineered to have high densities of nitrogen-vacancy centres show levels of brightness varying significantly within single batches, or even within the same sample. Here we show that nearby nitrogen impurities quench emission of nitrogen-vacancy centres via non-radiative transitions, resulting in a reduced fluorescence quantum yield. We monitored the emission properties of nitrogen-vacancy centre ensembles from synthetic diamond samples with different concentrations of nitrogen impurities. All samples were irradiated with high energy electrons to create high densities of nitrogen-vacancy centres relative to the concentration of nitrogen impurities. While at low nitrogen densities of 1.81 ppm we measured a lifetime of 13.9 ns, we observed a strong reduction in lifetime with increasing nitrogen density. We measure a lifetime as low as 4.4 ns at a nitrogen density of 380 ppm. The change in lifetime matches a reduction in relative fluorescence quantum yield from 77.4% to 32% with an increase in nitrogen density from 88 ppm to 380 ppm, respectively. These results will inform the conditions required to optimise the properties of diamond crystals devices based on the fluorescence of nitrogen-vacancy centres. Furthermore, this work provides insights into the origin of inhomogeneities observed in high-density nitrogen-vacancy ensembles within diamonds and nanodiamonds.

Assessment of the influence of intensity of optical signal on the probability of erroneous data registration in a single-photon communication channel

When measuring low-power optical signals in single-photon communication channels, the receiving modules must ensure the minimum probability of erroneous data recording. In this regard, it is advisable to use photon counters. They are highly sensitive, but are characterized by data recording errors. The aim of the work was to determine the effect of intensity of optical signal on the probability of erroneous data recording in a single-photon communication channel with a receiving module based on a photon counter.Based on the results of experimental studies, the dependences of the probability of erroneous registration of binary symbols «0» Perr 0 on the intensity of the optical signal J0 , used to transmit these symbols for various supply voltages of the avalanche photodetector U, were obtained. It was found that with an increase of intensity of the optical signal, the dependences Perr 0(J0) first decrease, reaching their lowest value, and then increase. The performed assessment showed that the lowest probability of erroneous registration the binary symbols «0» for the investigated communication channel is equal to 17,56 • 10-2 and corresponds to J0 = 52,41 • 10-2 rel. units and U = 52,54 V.

Measurement of the Probability of a Binary Symbol «0» Erasing in a Single-Photon Asynchronous Communication Channel with a Receiver Based on a Photon Counter

Receiving modules of single-photon communication channels should provide the least loss of transmitted information when measuring low-power optical signals. In this regard, it is advisable to use photon counters. They are highly sensitive, but are characterized by data logging errors. Therefore, the purpose of this work was to investigate the effect of the intensity of the recorded optical radiation during the transmission of binary symbols «0» on the probability of erasing these symbols in a single-photon communication channel containing a photon counter based on an avalanche photodetector as a receiving module with a passive avalanche suppression scheme.The lower and upper threshold levels of pulses recorded at the output of the photon counter, as well as the statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter when registering binary symbols «0» Pst0( N ) and «1» Pst1( N ) were determined. For this, a technique was used to reduce information loss. As a result, the minimum probability of erasing binary symbols «0» P(–/0) was achieved.The performed experimental results showed that to achieve the minimum probability of erasing binary symbols «0» P(–/0) = 0,11·10−2, it is important to select not only the intensity of the used optical radiation J , but also the supply voltage of the avalanche photodetector U, at which the dead time of the photon counter is −2 minimal, and its quantum detection efficiency is maximum: J0 ≥ 98,94·10−2 rel. units and U = 52,54 V.

Research on joint coding for underwater single-photon video communication

In order to achieve effective and reliable video transmission, a video joint coding scheme based on dictionary learning and the concatenation of LT code and LDPC code is proposed for underwater single-photon com-munication system. Sparse coding based on dictionary learning greatly compresses the amount of video data. According to the deletion characteristic of underwater single-photon channel, using the LT-LDPC channel concatenated coding method can overcome the disadvantage of excessive decoding overhead of LT code. Aiming at the problem of decoding failure probability of LT coding, a double feedback mechanism for decoding success is proposed. The experimental results show that when the channel error rate is in the order of 10-2 and the video compression rate is 75.6%, the video frames can be reconstructed with an average peak signal-to-noise ratio (PSNR) of 37.4921 dB.

Effects of Oceanic Turbulence on Orbital Angular Momenta of Optical Communications

The propagation properties of Laguerre-Gaussian beams in oceanic turbulence are investigated for both single-photon and biphoton cases. For single-photon communication, the channel capacity and trace distance are employed, both of which effectively reveal the communication performance via different viewpoints. For the biphoton case, we consider distributions of quantum resources including entanglement and quantum coherence. Turbulence conditions with a larger inner-scale and anisotropic factors, higher dissipation rate of kinetic energy, lower dissipation rate of the mean-squared temperature, and lower temperature-salinity contribution ratio combined with longer wavelength and an appropriate range of optimal beam width are beneficial to communication performances. Our results provide theoretical significance to improve the orbital-angular-momentum communication via oceanic turbulence.

Method of Achieving the Least Loss of Information in an Asynchronous Binary Single-Photon Communication Channel with a Receiver Based on a Photon Counter

Receiving modules of single-photon communication systems should provide the smallest loss of transmitted information when measuring low-power optical signals. In this regard, it is advisable to use photon counters. They are the most highly sensitive, but characterized by data recording errors. The aim of this work was to develop a method for determining the intensity of recorded optical signal in a singlephoton communication channel with a receiving module based on a photon counter, which ensures the least probability of erroneous registration of transmitted binary symbols. Methods of achieving the least loss of information in asynchronous photon binary communication channel with a receiver-based photon counter has been developed. A device for implementing this methods has been created. The method is based on using the statistical distribution of the mixture of the number of dark and signal pulses received at the output of the photon counter when registering binary symbols 0 P st 0 ( N ) and symbols 1 P st 1 ( N ). The essence of the method consists in determining the intensities of optical signals for transmitting binary symbols (0 and 1) and threshold levels of the pulses N 1 and N 2 registered at the output of the photon counter. The method allows to determine the lower and upper threshold levels of recorded pulses and the intensity of optical signals in the transmission of binary data. Moreover, the probability of erroneous registration of binary symbols is minimal.

Fluxonic Processing of Photonic Synapse Events

Much of the information processing performed by a biological neuron occurs in the dendritic tree. For artificial neural systems using light for communication, it is advantageous to convert signals to the electronic domain at synaptic terminals, so dendritic computation can be performed with electrical circuits. Here, we present circuits based on Josephson junctions and mutual inductors that act as dendrites, processing signals from synapses receiving single-photon communication events with superconducting detectors. We show simulations of circuits performing basic temporal filtering, logical operations, and nonlinear transfer functions. We further show how the synaptic signal from a single photon can fan out locally in the electronic domain to enable the dendrites of the receiving neuron to process a photonic synapse event or pulse train in multiple different ways simultaneously. Such a technique makes efficient use of photons, energy, space and information.

Non-Kolmogorov atmospheric turbulence and orbital angular momentum of entangled states for optical communication

We extend the theory of detection probabilities of single-photon communication in turbulent atmosphere to the entangled case and derive analytical expressions for detection probabilities. We show that the rotational field correlation in the entangled case cannot be expressed as a straightforward extension from the disentangled case. By considering the orbital angular momentum (OAM) entangled Laguerre-Gaussian (LG) beams for illustration, we explore the effect of non-Kolmogorov atmospheric turbulence on the probabilities of both the biphoton detection and the single-photon detection. The entanglement of OAM LG beams contributes positively to the faithful detection probability. The change of maximal crosstalk probability in the detection process is also explored, which displays the non-linear dependence on the crosstalk quantum number.

Quantum key distribution in single-photon communication system

This paper presents a brief review of experimental studies in quantum cryptography and quantum key distribution by single photons in atmospheric and fiber-optic quantum communication channels. Two experimental setups for quantum key distribution developed at the Rzhanov Institute of Semiconductor Physics SB RAS are described. The dependence of the quantum key distribution rate on the average number of photons μ in the laser pulse was studied. For μ > 0.3, there is a discrepancy between theory and experiment. The reasons for this are, first, the nonzero probability of multiphoton pulses occurring in quantum transmission and counted as single photons by single-photon detectors and, second, the rejection of the cases where several single-photon detectors click simultaneously in quantum key sifting because the measurement result is not determined in these cases.

Single Photon Communication with Avalanche Diodes and the General Basics of Photon Counting

Single photon communication (SPC) already exists in several applications in laboratory and even outdoor conditions. In the field of quantum cryptography SPC experiments are part of military applications too. There are several methods to detect every single impacting photon in such an experiment. Mostly photomultiplier tubes (PMT) are used. In some cases single photon avalanche diodes (SPAD) are more suitable for photon detection. Both the SPADs and PMTs have advantages and disadvantages. Usually PMTs have much larger detection areas than SPADs, but most of the PMTs detection efficiency peaks at 400 nm wavelength compared to the SPADs, where it peaks at 600–700 nm wavelength. For long distance laser measurements the higher wavelength is more suitable due to the Rayleigh scattering, but the detection hole of SPAD is very tight, which is why it is really hard to target the laser punctually without an optical gyroscope.

Second Harmonic Generation in the Background of Photon Counting

This article will show an application of photon counting using an experiment with a Second Harmonic Generation (SHG) to take a look at the basics of single photon communication. This will be an opportunity to open the way for long distance single photon laser communication between unmanned robotic vehicles. This article also gives an insight into a similar, but smaller setup towards the application on unmanned robotic vehicles. In this work measurements by SHG from Si (111) sample have been done with all polarization configurations with the help of a MIRA 900 type Ti: Sapphire laser. The other part of the experiment was carried out with an SR 400 photon counter device which was used for counting the impacting pulses with the help of a photomultiplier tube (PMT).

On the quantum-channel capacity for orbital angular momentum-based free-space optical communications

Inspired by recent demonstrations of orbital angular momentum-(OAM)-based single-photon communications, we propose two quantum-channel models: (i) the multidimensional quantum-key distribution model and (ii) the quantum teleportation model. Both models employ operator-sum representation for Kraus operators derived from OAM eigenkets transition probabilities. These models are highly important for future development of quantum-error correction schemes to extend the transmission distance and improve date rates of OAM quantum communications. By using these models, we calculate corresponding quantum-channel capacities in the presence of atmospheric turbulence.

Design and Implementation of Full-link Simulation System of Space-to-ground Optical Communication

目前空——地单光子通信系统的设计大都基于分系统进行性能分析, 很难给出系统级的性能参数, 为系统设计优化提供可信的支持. 为了综合评价空——地单光子通信的系统性能, 采用全链路系统仿真的方法, 基于离散事件仿真器构建空——地单光子通信仿真的全链路系统, 通过蒙特卡洛方法仿真模拟捕获、瞄准、跟踪过程和单光子通信过程, 有效模拟各子系统间的耦合关系, 对空——地单光子通信系统的关键性能参数做出综合、准确的评价, 为系统设计和优化提供依据.

Up-conversion single-photon detector using multi-wavelength sampling techniques

The maximum achievable data-rate of a quantum communication system can be critically limited by the efficiency and temporal resolution of the system's single-photon detectors. Frequency up-conversion technology can be used to increase detection efficiency for IR photons. In this paper we describe a scheme to improve the temporal resolution of an up-conversion single-photon detector using multi-wavelength optical-sampling techniques, allowing for increased transmission rates in single-photon communications systems. We experimentally demonstrate our approach with an up-conversion detector using two spectrally and temporally distinct pump pulses, and show that it allows for high-fidelity single-photon detection at twice the rate supported by a conventional single-pump up-conversion detector. We also discuss the limiting factors of this approach and identify important performance-limiting trade offs.

Atmospheric Turbulence and Orbital Angular Momentum of Single Photons for Optical Communication

The effects of propagation through random aberrations on coherence for single-photon communication systems based on orbital angular momentum states are quantified. A rotational coherence function is derived which leads to scattering equations for azimuthal modes of different orbital angular momentum states. The effect on a single-photon communication system is quantified using the channel capacity. The work shows that the decoherence effect of atmospheric turbulence on such systems is important even for weak turbulence.