This PDF file contains the front matter associated with SPIE Proceedings Volume 11339, including the title page, copyright information, table of contents, and author and conference committee lists.

In this paper, we study unitary operators and the superposition of unitary operators. We calculate the the superposition of unitary operators and find that some unitary operators superposition is also unitary operator. Furthermore, via this property, we discuss the set of orthogonal maximally entangled states. For 2,3,4,5-qubit, we introduce the complete sets of orthogonal maximally entangled states. We find that orthogonal basis of maximally entangled states can be divided into k subspaces. It is shown that some entanglement properties of superposed state in every subspace are invariant.

Continuous-variable quantum key distribution (CVQKD) with a real local oscillator (LO) is confronted with new security issues attributed to the reference pulses transmitted together with quantum signals over the insecure quantum channel. This paper proposes a method of phase attack on reference pulses of the CVQKD with real LOs. Under the phase attack, the phase drifts of reference pulses are manipulated by eavesdroppers so that the phase compensation error is increased. Consequently, the secret key rate is reduced because of the imperfect phase compensation for quantum signals. Based on the noise model of imperfect phase compensation, both the parameters of actual transmittance and actual excess noise are deduced from the phase compensation accuracy, and then they are compared with those estimated by training signals. The simulation results show that the secret key rate calculated from the theoretical parameters is consistent with the one estimated by training signals.

A high speed comparator applied to GHz gated single photon detection technology is proposed. The comparator is based on the combination of pre-amplification and dynamic regenerative latching structures, resulting in an effective improvement in response speed. In this paper, an analysis on the transmission delay of the dynamic latch comparators is presented. The proposed circuit is implemented in 350 nm CMOS technology and occupies an active area of 0.012 mm². The delay of the whole detection system is approximately 256ps and the discrimination level of the proposed comparator is 50mV while consuming 4.7mW at supply voltages of 3.3V. The comparator can be used in a single photon gated detection system under 1 GHz condition.

The availability of quantum entanglement and EPR steering over a large frequency will bring further flexibility to the linking of quantum processes at different wavelengths, especially related to quantum memory. In this paper, a cascaded optical parametric system, with three interacting modes spanning two octaves of frequency difference, is investigated. This process combine degenerate optical parametric oscillation (OPO) and second harmonic generation (SHG), which is shown to be a useful way to obtain the quantum entanglement and EPR steering at three differing frequencies. The results are shown that compared to the normal only SHG, the existence of the OPO interaction eliminates the selfpulsing effect, and the threshold conditions of single OPO interaction is also changed due to the presence of the SHG. Above or below threshold, the system exhibits different quantum correlations features. The tripartite entanglement are only violated above threshold. The entanglement and EPR steering are both present in two conditions, but the system behaves totally different at the threshold. The effect of the ratio of loss rates of the three modes on the quantum correlations is also investigated. It is shown that the symmetric property of the quantum EPR steering is controlled by these ratios. This system is flexible to be adjusted and controlled, which potentially provides a significant resource for quantum correlations over a large bandwidth.

Two photonic qubits, initially maximally entangled in OAM modes of Hermite-Gaussian HG vortex beam, propagating through non-Kolmogorov turbulence are investigated numerically. The influences of turbulence parameter (i.e., the generalized exponent, the outer scale of turbulence, and the inner scale of turbulence) and OAM values on the entanglement evolution of two photon are investigated and compared with those of the Laguerre-Gaussian (LG) beam. The results indicate that the OAM entanglement to be more robust in turbulence for the higher OAM values, the higher generalized exponent. Moreover, the influence of the turbulence inner scale and outer scale on OAM entanglement can be ignored. The OAM entanglement of HG vortex beam is better than the OAM entanglement of LG beam for resisting the entanglement decoherence of atmosphere turbulence under the same conditions.

The CMOS single photon avalanche photodiode (SPAD) image sensor, as the third-generation solid-state imaging device, features single photon response capability, picosecond magnitude time resolution and micron-scale spatial resolution. The device is currently the mainstream ideal device for single-photon, picosecond time-resolved transient imaging, and is gradually applied to time-resolved spectral measurement, 3D ranging and imaging, fluorescence lifetime imaging, quantum imaging sensing and such low light or even single photon ultrafast imaging. In this paper, we introduce the research progress of the CMOS SPAD image sensor, and the challenges and solutions of the device are analyzed. In the past years, the mainstream CMOS SPAD image sensor features front-illuminated SPAD and the planar-structure pixel. However, for the planar-structure pixel, in order to make the SPAD with higher fill factor, reducing the duty cycle of the readout electronics within the pixel is the usual method, which to some extent sacrifices the function of reading electronics. In addition, the lower process node was used to improve the integration of electronics, but the high dark count rate was easily caused; The integration of micro-lens array in pixels was also used, but limits the flexibility of pixel size and increases the costs. Compared with planar-structure pixel, the pixel scheme of the three dimensional (3D) stacked structure, integrates the SPAD device and the readout electronics in the pixel correspondingly on the vertically coupled two wafers, which eliminates the problem of duty cycle of the readout electronics within the pixel and would be the development direction in the future.

In order to improve the security of traditional encryption systems, hyper-chaotic systems are introduced into the field of quantum image encryption. Firstly, the image is bitwise XOR by He fractional order hyper-chaotic Rabinovich system, and then the color image is represented as a quantum superposition state. The quantum image is scrambled by the unitary matrix generated by Logistic hyper-chaotic sequence, and then a hyper-chaotic sequence is generated to randomly replace the red, green and blue primary colors of each pixel to achieve the purpose of quantum image encryption. Finally, numerical simulation experiments are carried out on a computer. The experimental results show that the histogram of the encrypted image is flatter and even, the pixels are evenly distributed between 0 and 255, the correlation between adjacent pixels of the image is low. The average correlation coefficients of the red, green, and blue pixels of the encrypted image are 0.0012, 0.0025, and 0.0018. The system has high key sensitivity and can effectively resist statistical analysis attacks. The algorithm has good security and robustness.

In the free-space quantum communication, the performance of communication systems has a great degradation due to the atmospheric effects, such as atmospheric absorption, scattering and turbulence. However, quantum signals with different wavelengths is differently affected by atmospheric characteristics. In this paper, in order to investigate the effects of different wavelengths quantum signals on free-space quantum key distribution, an entanglement-based continuous variable quantum key distribution transmission model is established. Considering the influence of various atmospheric effects on quantum signals, the secret key generation rates are calculated though the homodyne detectors. The simulation results show that the long-wavelength signal can enhance the secret key generation rates at the same transmission distance. Therefore, the long-wavelength signal is more suitable for the free-space quantum transmission.

In this paper, we have calculated the entanglement degrees of a two-level atom in the one-dimensional photonic crystals heat reservoir, researched the effect of parameter q on the quantum entanglement degrees, and given the quantum entanglement degrees curves with time evolution. We have taken the parameter q=1, 2, 3.5 and 8.5. Our results show when the parameter q=2, keep the time of entanglement degrees near E=1 longest, it is helpful to quantum communication. Furthermore, we have designed the one-dimensional photonic crystals heat reservoir, which meet the parameter q=1, 2, 3.5 and 8.5. These can guide the fabrication of quantum devices based on photonic crystals.

Microwave is widely used in present navigation system. It works well, yet it faces precision limit and other challenges. Quantum entanglement has been applied in various fields and resulted in quite remarkable improvement, especially in precision performance, as it can break quantum noise limit. Hence, we attempt to apply quantum entanglement to enhance merits of navigation system performed in microwave regime. This paper introduces principles of quantum microwave entanglement prepared by electro-opto-mechanical converters in detail, which is also adopted by quantum illumination. Meanwhile, a navigation scheme enhanced by quantum microwave entanglement is proposed. The working principles of the scheme, especially those of location, range finding and direction finding, are analyzed in detail. Besides, we compare navigation scheme of quantum microwave entanglement with present navigation scheme. It shows that navigation merits have been enhanced by quantum microwave entanglement, and it may be regarded as a candidate of new navigation method.

How to realize high-fidelity non-classical quantum state transformation in cavity electro-opto-mechanical system is a hot issue in the field of quantum information research. Adjusting the range of the optical detuning amount can indirectly realize the non-classical conversion of the microwave and the optical field. This paper analyzes the effect of driving light detuning on microwave and light conversion. This research work has theoretical and practical significance for the application of quantum state conversion technology of cavity electro-opto-mechanical system in precision quantum measurement and quantum information processing.

We proposed new light pulses to create a quantum coherent superposition state by using the invariant-based inverse engineering in a resonant three-level system, where physical imperfections such as the frequency detuning and variations in Rabi frequencies were concerned. Simulation results show that the fidelity of creating a superposition state of more than 98% can be achieved over a frequency detuning of ±18 MHz in 4 μs. The pulses are robust against the spatial inhomogeneity or instantaneous fluctuations in laser intensity. Comparisons of our pulses with other pulses show that our pulses are much more robust in terms of both the frequency detuning and laser intensity variations. Such features make our pulses an effective alternative as the spectral hole-burning pulses to reduce the number of repetitions of pulses, and can also be applied to initialize the multiple qubits where the driving frequency varies with time or position in superconducting transmon qubit systems.

Quantum walks (QWs) provide a powerful tool as a quantum simulator to study topological phases. However, some interesting topological phenomena in the two dimensional (2D) QW that do not exist in the one dimensional case, e.g., the edge-state-enhanced transport, have not been demonstrated experimentally. Here we have observed 2D topological bound states with vanishing Chern numbers and confirmed the robustness of these bound states with respect to perturbations and disorder, which go beyond what has been known in static systems and are unique to periodically driven systems. Our studies open up an avenue to explore topological properties in multidimensional QWs.

InGaAs/InP avalanche photodiodes (APDs) are one of the optimum choices for the practical applications requiring singlephoton detection in the near-infrared. In this paper, we demonstrate a high-speed single-photon detector (SPD) based on an APD working at room temperature with high detection efficiency. Ultrashort pulses are employed as the gating signals applied on the APD to reduce the avalanche time, efficiently reducing the error counts which include the dark count and afterpulses. Low-pass filters are cascaded to remove the spike noise down to the thermal noise level, guaranteeing the extraction of the photon-induced avalanche signal. Finally, the detection efficiency of 50.4% at 1310 nm is achieved with the dark count rate (DCR) of 3.1×10^-4/gate and the afterpulse probability (AP) of 5.6% at 1 GHz at the temperature of ~21℃. This room-temperature SPD with such high performance could further expanding the APD’s applications in ranging and imaging systems.

Traditional lidar is not effective in detecting small long-range targets with weak echo signals. Geiger-mode Avalanche Photodiode (Gm-APD) single photon detector has super high sensitivity. By adding photon orbital angular momentum modulation module, a photon-counting chirped amplitude modulation lidar with high sensitivity ranging function is designed. Based on the characteristics of photon orbital angular momentum space transmission, a special demodulation method is used to realize the spatial separation of noise and signal. The above scheme achieves the goal of high sensitivity ranging detection. The simulation results show that the scheme can improve the signal-to-noise ratio of the system effectively and realize the high-sensitivity ranging function of small target in long distance.

We have investigated the modification of self-assembled InAs/GaAs quantum dots (QDs) by in situ pulsed laser irradiation. The QDs were fabricated by molecular beam epitaxy (MBE) in Stranski-Krastanov mode at 480℃ and then at the same temperature the pulsed laser was in situ introduced to modify the QDs with different energy. The dependence of morphology evolution on irradiation energy was carefully studied by AFM testing. The results show that laser excitation can enable both desorption and diffusion of In atoms which may induce strong modification on the InAs QDs. For irradiation of a moderate energy, the 3D dot-like InAs QD will transform into 2D oval-shaped island; Once the irradiation energy is high enough, the InAs QDs will be completely removed off from the surface. The involved mechanism is also discussed. Herein, we have proposed a new approach of fabricating QDs which is high-efficient, pollution-free, oxidation-free and defect-resistant and it is believed in the near future, it may find wide applications in both the fundamental physics research and emerging device manufacture.

A quantum ranging scheme based on dual-path entangled microwaves and coherent detection is proposed to avoid the difficulties of low security, limited precision in traditional radio navigation ranging schemes, being sensitive to multipath effect and the poor performance of existing quantum ranging schemes in current navigation systems. Based on the characteristic that orthogonal quadrature of dual-path entangled microwaves has the largest cross-correlation when the two signals are synchronized, coherent detection is used to get the reference electromagnetic information and calculate the time delay. Based on the principle of pseudo code acquisition and tracking of satellite navigation receiver, a synchronization scheme of time delay is designed, which can acquire the accurate distance ranging. Simulated analysis is implemented in precision and anti- interference, which provide theoretical support for application of dual-path entangled microwaves and a new type of quantum navigation position technology.

Photon-counting imagers such as photonic cameras and imaging spectroradiometers have been improved rapidly for cutting-edge applications such as multi-photon microscopy, super-spectral imaging, hyper-spectral LIDAR, and so on. At low light level, the optical radiant power (in watts) can be interpreted as photon rate (in photons per second) and this would make more sense especially when the photonic nature of individual photon is crucial for in-depth analyses. Similarly, the spectral irradiance and radiance can be formulated into spectral photon irradiance (or spectral photon flux) and spectral photon radiance, respectively, for few photon applications. At the National Institute of Metrology of China, the calibration facility of the spectral quantum efficiency for the photon-counting detectors has been established with uncertainties of <0.5%, traceable to both the classical absolute cryogenic radiometer and the calibration facility based on correlated photons, with the calibration using these two methods agreed within 0.3% @ 633 nm. However, the three major kinds of photoncounting detectors including silicon avalanche photodiodes (Si-APDs), photomultipliers tubes (PMTs) and superconducting single photon detectors (SSPDs) can be well calibrated for spectral photon rate measurements but not spectral photon irradiance (or spectral photon flux) or spectral photon radiance. For instance, Si-APDs usually have very small effective sensing sizes, PMTs have significant non-uniformity over the sensing area, and SSPDs need bulky cooling systems. Photon counting detectors with mm-sized uniform sensing areas can be developed based on photomultiplier tubes and the non-uniformity of the quantum efficiency was measured to be better than 3% at 633nm. The spectral quantum efficiency of the photon counting detectors can be further determined over the 300 nm ~ 1000 nm spectral range and the non-uniformities are less than 5%. Precision apertures with their areas carefully measured can be installed before these photon counting detectors for spectral photon irradiance (or spectral photon flux) measurements. For instance, the photon counting detectors with precision apertures can be applied to measure the spectral photon irradiance (or spectral photon flux) of an integrating sphere illuminated with a wavelength-tunable monochromatic light when placed at certain distance from the exit of the integrating sphere. The spectral photon radiance can also be evaluated when a precision aperture is installed at the exit of the integrating sphere. The calibrated integrating sphere source can then be used as standard spectral photon irradiance (or spectral photon flux) and spectral photon radiance sources for photon-counting imager calibration.

The generation and detection of dual-path entangled quantum microwave are widely investigated in recent years. Nevertheless, entangled quantum microwave is usually expressed and processed in quantum frame. In order to observe the entangled information and apply it to some fields, we also need to measure it and transform it into the form of electric signals. Therefore, we investigate the time domain waveform of dual-path entangled microwave signals from the view of measurement. In different measurement interval, the waveform of one-path entangled microwave signal is completely random. While the waveforms of two-path entangled microwave signal always meet the relationship of positive correlation or negative correlation. The randomicity and correlativity is the most intrinsic characteristic of entangled microwave signals. By analyzing the relation of mean value, fluctuation, entangled photon number and squeezed parameter, we explain the essence of the quantum stochastic and correlated characteristics in physics. A more intuitive understanding of entangled microwave signals would be felt in this research, which makes us easier to utilize the characteristic for the potential applications.