High-order Laguerre-Gaussian (LG) vortex beams are indispensable for cutting-edge applications in quantum entanglement, high-capacity information encoding, gravitational wave detection, and as amplifier seed sources. However, existing generation methods face significant trade-offs between achievable mode orders, particularly for high and tunable radial indices (p), and beam quality. Here, we overcome these limitations by demonstrating a gain-engineered Nd:YVO4 laser that directly generates high-order Hermite-Gaussian (HGm,n) modes with fully two-dimensional (2D) tunable indices (m = 0-2, n = 0-5). These modes are subsequently converted into highquality LGp,l vortex beams (p = 0-2, l = 0-3) exhibiting 2D tunability. While conventional non-collinear pumping intuitively suggests 2D HGm,n mode generation, cylindrical cavity symmetry renders it equivalent to a tilted one-dimensional (1D) configuration, causing 1D modes to dominate in mode competition due to their superior pump overlap. Our core innovation is a hybrid pumping scheme that strategically combines annular and 2D non-collinear geometries to manipulate the intracavity gain distribution. This approach enables 2D HGm,n modes to decisively outcompete their 1D counterparts. Precise control over the HGm,n indices is achieved through output mirror tilting. By leveraging rigorous q-parameter analysis and inverse optical design, we ensure optimal mode matching between the intracavity field and an external astigmatic mode converter, facilitating the efficient generation of LGp,l modes with continuous index tunability and excellent beam quality. The helical phase structure of the generated vortex beams is experimentally verified via off-axis interference with a reference plane wave. This work establishes a robust and scalable approach for generating high-order, index-tunable structured light, providing a valuable benchmark for the development of advanced vortex laser sources across diverse spectral regions.

Precise nanofilm birefringence characterization is essential for high-sensitivity polarization response and strong anti-interference detection in photodetectors. We present a high-sensitivity and high-resolution birefringence coefficient determination system for nanometer-level membranes based on weak measurement, addressing the sensitivity-resolution trade-off. A tunable bandwidth light source is exploited to achieve simultaneous and complementary measurements of momentum (P-pointer) and intensity (I-pointer), enabling calibration-free operation across various bandwidths, and to realize high-precision phase difference monitoring of the measured membranes. This method maps the birefringence effect to a weak value amplified signal of spectral shift and light intensity. The optimal resolution, achieved at a spectral width of 6 nm, is 1.12 & times; 10(-8) RIU, while the optimal sensitivity is achieved when the light source is a narrow-linewidth coherent laser, reaching 4710 mV/RIU. The linear range of the system covers a broad birefringence coefficient range for crystals, from 10( -6) to 0.1. Furthermore, the auxiliary optical path eliminates substrate interference, achieving a detection limit of birefringence coefficient as low as 10 - 8 RIU. This approach, characterized by high precision, high sensitivity, and strong robustness, provides an effective solution for the detection of optical nano-thin membrane parameters.

Quantum weak measurement technology has significantly advanced the detection limits of quantum precision measurement due to its minimal disturbance to the measured system and the weak value amplification effect. This technique has been successfully applied to phase difference and time difference measurements, resulting in a series of important achievements. Previous standard weak measurement typically uses only a single momentum parameter as the measurement pointer and relies on a single weak interaction to detect minute phase shifts. Although some studies have attempted to introduce quantum resources to further enhance the amplification factor and measurement precision, their practical applications are hindered by the challenges associated with quantum state preparation. Therefore, practical quantum weak measurement systems still require in-depth research and exploration to overcome these technical bottlenecks. In this study, we propose and experimentally validate a dual-parameter quantum weak measurement scheme based on tunable spectral control and iterative weak interactions. Theoretical analysis demonstrates that adjusting the spectral width and the number of weak interactions can effectively enhance the weak value amplification effect. Experimentally, a phase weak measurement system based on iterative weak interactions is constructed using a tunable light source as an optical input. The setup includes three sets of half-wave plates (HWPs) to realize triple weak interactions. By fixing the post selection angle and rotating the HWPs to introduce a weak phase delay, high-precision detection of the phase shift is achieved by monitoring the variations of both the spectral shift and light intensity. Experimental results indicate that at a spectral width of 700 GHz, the momentum parameter M achieves an optimal phase difference measurement accuracy of 4.06 & times; 10(-8 )rad, which is 2.78 times higher than that of single weak interaction (SWI). As the spectral width decreases, the signal-to-noise ratio (SNR) gradually degrades, causing the shift signal of parameter M to be submerged in the spectrometer's electronic noise. This necessitates a switch to the intensity parameter I for detection. When a narrow-linewidth source with a linewidth of 500 kHz is used, the intensity parameter I enables phase difference measurements at a level of 5.99 & times;10-7 rad while maintaining an SNR of 17.4 dB. Its measurement precision is 2.97 times higher than that of SWI. In optical experiments, the optical phase can serve as a proxy for other physical quantities such as displacement, temperature, and magnetic field strength. Therefore, this scheme provides crucial technical support for enhancing quantum precision sensing in practice.

Objective Quantum weak measurement is a measurement technique based on minimal intrusion and the weak value amplification (WVA) effect, which significantly expands the capability of quantum precision measurement. Quantum weak measurements have been applied to tiny-phase measurements and have yielded a series of results. Previous standard weak measurements primarily used spectral or CCD pointers to achieve precise measurements of tiny phases under a single weak interaction (SWI). However, a trade-off between enhancing the amplification factor (known as the anomalous weak value) and the post-selection probability is encountered in SWIs. Because of the difficulty in enhancing both simultaneously, the extraction of the anomalous weak value and the measurement precision are limited. This issue is typically alleviated using quantum resources. However, difficulties in preparing quantum resources restrict their practical applications. Hence, practical quantum weak measurement systems must be further investigated to overcome these limitations. Methods In this study, an enhanced phase weak measurement method based on multiple weak interactions (MWIs) is proposed and demonstrated. The evolution of the intensity pointer was analyzed theoretically and a formulation for enhanced WVA was derived. A system for enhanced phase weak measurements based on MWIs was constructed using continuous coherent light as the incident source. This setup employs double weak interactions with two sets of half-wave plates (HWPs) as well as an avalanche photodiode (APD) as the intensity pointer. The post-selection angle was fixed, and the HWP was tilted to introduce a weak phase delay for the measurement. Meanwhile, the phase delay was detected precisely by recording changes in the light intensity. By maintaining a constant phase delay and adjusting the post-selection angle, anomalously weak values were extracted with a high signal-to-noise ratio (SNR). Results and Discussions Owing to the double weak interactions, the intensity shift is greater than that resulted under the SWI (Fig. 4). The symmetrical post-selection intensity contrast ratios exceed those under the SWI by approximately two folds (Fig. 5), thus indicating that the double-weak-interaction scheme offers a higher measurement sensitivity. At three post-selection angles of 0.002, 0.004, and 0.007 rad, the intensity uncertainties of the double weak interactions are 0.006, 0.015, and 0.040 mV, respectively (Fig. 6), and the phase precisions are 6.00x10-7, 7.76x10-7, and 9.46x10-7 rad, respectively. Compared with the SWI, the double weak interactions improved the phase precision by approximately an order of magnitude. Under the double weak interactions, an anomalously weak value of 239 is obtained with a high SNR of 18.2 dB for a post-selection angle of 0.0084 rad. Decreasing the post-selection angle to 0.002 rad while the SNR remains at 9.8 dB results in a higher anomalous weak value of 993 (Fig. 7). Conclusions In this study, based on the amplification effect of anomalous weak values on the interaction parameters, an enhanced WVA scheme based on MWIs was theoretically and experimentally demonstrated and applied to ultraprecise phase measurements. Experimentally, coherent light with a linewidth of 400 kHz was used as the incident light source and an APD was utilized as the intensity pointer, which is different from previous spectral detection schemes. By developing the MWI theory and experimental scheme as well as realizing double weak interaction (N=2) measurements, the experimental results show that the phase measurement sensitivity is significantly better than that achieved under SWIs. In particular, an optimal measurement precision of 6.0x10-7 rad is achieved at a post-selection angle of 0.002 rad, which is approximately an order of magnitude higher than that achieved under an SWI. Additionally, based on a high SNR of 9.8 dB at a post-selection angle of 0.002 rad, an enhanced anomalous weak value of 993 is measured, which is approximately an order of magnitude greater than the standard weak measurement. The enhanced WVA scheme based on MWIs was validated via phase measurements, whereas the relationship between the phase and other physical quantities, such as displacement, temperature, and magnetic induction strength, can be established in optical experiments; thus, the scheme provides important technical support for practical enhanced quantum precision sensing.

Objective In the measurement of high-order photon correlation in light fields, high-precision time-to-digital converters (TDCs) are required to accurately measure the photon arrival time. The purpose of this study is to develop a multichannel high-precision TDC acquisition system that can accurately measure the photon arrival time using a field-programmable gate array (FPGA) hardware platform to support the high-order coherence of the light field, which can be accurately obtained via high-order photon correlation measurements of the light field. Methods In this study, a multichannel photon-arrival-time measurement design was implemented using XC7A100TFGG484 of the Artix-7 series. By combining "coarse counting" and "fine measurement" and developing the CARRY4 two-tap (CO0, CO3) structure, we constructed a tap delay chain for fine measurement, which improves the resolution of the TDC while overcoming the limitations of overfeeding. The dead time of the TDC was reduced to one system clock cycle using a switching input stage and dual-mode single- counter coding. The nonlinear delay of the delay cell was calibrated using the code-density calibration method, and the data were transmitted over gigabit ethernet. Subsequently, a test platform was constructed to continue implementing testing and data analysis for the TDC. Finally, the TDC device was verified using a time-correlated single-photon counting measurement system. Results and Discussions Accuracy was tested using a signal generator to generate a set of fixed time intervals from small to large to obtain the variation in the accuracy with the time interval. The maximum and minimum accuracies are approximately 25.6 and 20.1 ps, respectively (Fig. 10). The accuracy of the system was tested and counted for each of the eight channels, and the accuracy of the system was obtained as 26.3 ps (Fig. 11). The accuracy at different temperatures was measured at a time interval of 90.91 ns, and the variation in the accuracy error over the temperature range was 2.6 ps (Fig. 12). The results clearly indicate the low temperature sensitivity of the TDC designed in this study. The dead time was reduced to 5 ns in one system clock cycle by adding a switching input stage structure. The CARRY4 two-tap (CO0, CO3) structure was used to construct the tap delay chain, and a resolution of 34.7 ps was achieved. The differential nonlinearity (DNL) and integral nonlinearity (INL) of the system were obtained via code-density tests. For the 1-mode, the DNL and INL ranges are (-0.75tLSB, 1.5tLSB) and (-2tLSB, 2.8tLSB) , respectively. For the 0-mode, the DNL and INL ranges are (-0.76tLSB, 1.32tLSB) and (-1.2tLSB, 1.9tLSB), respectively (Fig. 13). Conclusions In this study, a TDC system for multichannel photon-arrival-time measurement was implemented based on an FPGA. The over-advanced feed of the delay unit and the issue of its nonlinear time delay being affected by temperature and voltage were addressed by performing calibration using a single CARRY4 two-tap (CO0, CO3) structure and the code-density calibration method, which in fact resulted in fine counting. An 8-bit 200 MHz system clock was used for coarse counting, and a combination of coarse and fine counting was performed to achieve high-precision measurements. The experimental results show that the developed eight-channel TDC system exhibits an average resolution of 34.7 ps, a timing accuracy of 26.3 ps, a dead time of 5 ns, as well as DNL and INL ranges of (-0.75tLSB, 1.5tLSB) and (-2tLSB, 2.8tLSB) for the 1-mode, respectively. For the 0-mode, the DNL and INL ranges are (-0.76tLSB, 1.32tLSB) and (-1.2tLSB, 1.9tLSB) , respectively. The TDC system implemented in this study combines the advantages of multichannel, high accuracy, and short dead time. Experimental validation was performed via time-correlated single- photon counting measurements, which indicated the practical requirement for higher-order photon-correlation measurements of the light field.

The bunching and antibunching effects of light fields reflect the spatiotemporal correlation of photons and are key indicators for distinguishing classical and non-classical quantum statistics. They play a crucial role in quantum information processing and precise measurement. In this paper, we investigate the super-bunching and antibunching effects of the full-time-delay higher-order coherence function g(n) for squeezed thermal states and squeezed number states based on a multi-cascaded Hanbury Brown-Twiss single-photon detection scheme.Under ideal conditions, the high-order coherence of squeezed thermal states and squeezed number states is analyzed by changing compression parameter r, average photon number alpha, and squeezed photon number n. The results indicate that when the compression parameter r is an element of[0,1], the squeezed thermal state exhibits a significant super-bunching effect, with super-bunching values of each order being g((2))=9.98x10(5), g((3))=8.98x10(6), g((4))=8.96x10(12), g(5)=2.24x10(14). The squeezed number state exhibits a continuous transition from antibunching to bunching behavior, with coherence degrees of different orders being g((2))is an element of[1.60x10(-5),1.09], g((3))is an element of[9.02x10(-6),1.16], g((4))is an element of[4.75x10(-6),1.22], and g((5))is an element of[9.39x10(-6),1.30]).Simultaneously, this study analyzes the high-order photon coherence of squeezed thermal states and squeezed number states under experimental conditions, with background noise gamma and detection efficiency eta taken into account. When detection efficiency is relatively low and background noise is substantial, the higher-order coherence of squeezed thermal states with smaller average photon number alpha is disturbed by background noise, but still maintains good super-bunching characteristics. However, when the average photon number alpha becomes large, which is limited by the dead time of single-photon detector, it is challenging to accurately obtain all the information about the squeezed number state light field, leading measurement results to deviate from the ideal values. When the average photon number is alpha=0.5, the super-bunching effects reach their maximum values of g((2))=2.149, g((3))=6.389(sic)g((4))=23.228, corresponding to the squeezing degrees S-(2)=5.47, S-(3)=4.86 and = 4.43, respectively. Furthermore, by adjusting the number of squeezed photons n and the squeezing degree of the squeezed number state light field, S, a continuous and wide-ranging change of high-order coherence function can be achieved, transforming from anti-bunching effect to super-bunching effect. Additionally, under the conditions of high environmental noise and low detection efficiency, higher-order coherence exhibits greater sensitivity to variations in optical field parameters than lower-order coherence. Furthermore, squeezed number states with multi-photon characteristics are less susceptible to disturbances from background noise, demonstrating stronger robustness.In addition, the variation characteristics of the high-order photon coherence function of the squeezed thermal state light field under the full time-delay conditions are investigated. The full time-delay high-order coherence g(n) of the squeezed thermal state light field near the coherence time range tau STS is significantly higher than that of the classical thermal state light field. Even when a significant time delay is introduced into one of the optical paths, partial synchronization among photons can still maintain a certain correlation strength. Although unsynchronized photons lead to an overall reduction in coherence, the coherence is still higher than the theoretical predictions for thermal states under identical conditions.Based on the theoretical framework established in this work, future experiments may focus on adjusting the pump power, intracavity loss, and crystal temperature of optical parametric amplifiers to jointly control the squeezing degree and mean photon number, enabling stable generation of squeezed thermal states in different parameter regimes. Additionally, the precise measurement of higher-order coherence can be achieved using cascaded HBT detection systems with multiple inputs and high temporal resolution.In summary, by considering environmental noise, detection efficiency, and time delay, and by adjusting the average photon number, the number of squeezed photons, and the squeezing parameters, this method can prepare super-bunching squeezed thermal states and squeezed number states, whose higher-order coherence can be continuously adjusted over a wide range, thereby facilitating efficient quantum state preparation and manipulation, as well as high-resolution quantum imaging.

Continuous variable quantum random number generator (CV-QRNG) has become one of the most actively developing QRNG schemes due to its excellent application prospects. Whether it is device-trusted or device-independent, the improvement of the quantum entropy relative to side information is a key bottleneck to be broken through in the CV-QRNG scheme, particularly against metrological-grade entropy evaluation. In this work, initial value hypersensitivity chaotic amplification of quantum shot noise is proposed to enhance quantum noise entropy content in CV-QRNG. A noise-added Lang-Kobayashi model is established to simulate, and multiple indexes to quantitatively evaluate, the divergence, convergence, and entropy increase in the dynamic process from quantum shot noise to a chaos-steady state in a chaotic laser. Based on homodyne detection of quadrature fluctuations of four independent quantum sideband modes of a chaotic laser, an extract ratio of 89% and a real-time yield of QRN of 21.28 Gbps are attained on the strength of chaos amplification of vacuum noise. The quantum classical noise ratio (QCNR) and the flatness of the entropy source are significantly enhanced and the relief of the RF amplifier and logic resource in post-processing supports high robustness, integrability, and scalability. The amplification effect of chaos on quantum fluctuations is similar to a passive and uncontrollable Gaussian modulation, which may play a role in CV quantum communication.

Secure communication is critically dependent on high-speed and high-security quantum random number generation (QRNG). In this work, we present a responsive approach to enhance the efficiency and security of QRNG by leveraging polarization-controlled heterodyne detection to simultaneously measure the quadrature amplitude and phase fluctuations of vacuum shot noise. To address the practical non-idealities inherent in QRNG systems, we investigate the critical impacts of imbalanced heterodyne detection, amplitude–phase overlap, finite-size effects, and security parameters on quantum conditional min-entropy derived from the entropy uncertainty principle. It effectively mitigates the overestimation of randomness and fortifies the system against potential eavesdropping attacks. For a high-security parameter of 10−20, QRNG achieves a true random bit extraction ratio of 83.16% with a corresponding real-time speed of 37.25 Gbps following a 16-bit analog-to-digital converter quantization and 1.4 GHz bandwidth extraction. Furthermore, we develop a deep convolutional neural network for rapid and accurate entropy evaluation. The entropy evaluation of 13,473 sets of quadrature data is processed in 68.89 s with a mean absolute percentage error of 0.004, achieving an acceleration of two orders of magnitude in evaluation speed. Extracting the shot noise with full detection bandwidth, the generation rate of QRNG using dual-quadrature heterodyne detection exceeds 85 Gbps. The research contributes to advancing the practical deployment of QRNG and expediting rapid entropy assessment.

Continuous-variable quantum random number generator (cv-QRNG) has attracted much attention due to its convenient state preparation and high measurement bandwidth. Chip-size integration of this type of QRNG is expectable because all components involved have been integrated on a single chip recently. Most of the existing schemes, including all existing commercial schemes, usually use a once-and-for-all approach to evaluate quantum entropy. In this work, we propose a double-level parallel cv-QRNG scheme that integrates real-time phase-space monitoring and entropy evaluation. By using dynamic threshold monitoring and self-adapting scaling of Toeplitz matrix, the security and generation rate of QRNG can be enhanced simultaneously.Experimentally, a parallel extraction system of vacuum state double quadratures and multiple sideband modes is constructed based on heterodyne, providing sufficient raw data for high-precision and high-speed tomography reconstruction of quantum entropy source and parallel extraction of QRNG. Based on the statistical analysis of data under long-term stable operation of the system, dynamic KLD-sensitive security threshold for statistical distribution of Husimi-Q function of the entropy source is established. When a weak chaotic field is injected to simulate a thermal state attack, the KLD value jumps and quickly deviates from the steady state baseline, manifesting a sensitive identification of the attack. It is worth pointing out that the threshold parameter can be dynamically optimized according to the security requirements of actual application scenarios. An FPGA-based real-time feedback Toeplitz-hash extractor employs a maximum matrix bit-width truncation method to dynamically adjust Toeplitz matrix parameters. This optimization reduces the maximum extraction ratio interval from 6% to 1.8%, with all intervals below 1% for extraction ratios ≤76%, significantly mitigating entropy losses caused by discrete adjustment of the Toeplitz matrix, and achieving a minimum extraction ratio of 16.9%. This flexibility enables the system to accurately control the response sensitivity of abnormal signals while maintaining the real-time generation of quantum random bits. Finally, real-time generation rate of 17.512 Gbit/s is attained with security parameters at the level of 10–50 and the generated random numbers passed NIST SP 800-22, Diehard, and TestU01 standard tests.This research provides a technical path for real-time assessment of entropy source security in QRNG. The proposed scheme has good integrability and scalability, presenting a feasible solution for QRNG to enter the application stage.

Continuous-variable quantum random number generator (cv-QRNG) has attracted much attention due to its convenient state preparation and high measurement bandwidth. Chip-size integration of this type of QRNG is expectable because all components involved have been integrated on a single chip recently. Most of the existing schemes, including all existing commercial schemes, usually use a once-and-for-all approach to evaluate quantum entropy. In this work, we propose a double-level parallel cv-QRNG scheme that integrates real-time phase-space monitoring and entropy evaluation. By using dynamic threshold monitoring and self-adapting scaling of Toeplitz matrix, the security and generation rate of QRNG can be enhanced simultaneously. Experimentally, a parallel extraction system of vacuum state double quadratures and multiple sideband modes is constructed based on heterodyne, providing sufficient raw data for high-precision and high-speed tomography reconstruction of quantum entropy source and parallel extraction of QRNG. Based on the statistical analysis of data under long-term stable operation of the system, dynamic KLD-sensitive security threshold for statistical distribution of Husimi-Q function of the entropy source is established. When a weak chaotic field is injected to simulate a thermal state attack, the KLD value jumps and quickly deviates from the steady state baseline, manifesting a sensitive identification of the attack. It is worth pointing out that the threshold parameter can be dynamically optimized according to the security requirements of actual application scenarios. An FPGA-based real-time feedback Toeplitz-hash extractor employs a maximum matrix bit-width truncation method to dynamically adjust Toeplitz matrix parameters. This optimization reduces the maximum extraction ratio interval from 6% to 1.8%, with all intervals below 1% for extraction ratios <= 76%, significantly mitigating entropy losses caused by discrete adjustment of the Toeplitz matrix, and achieving a minimum extraction ratio of 16.9%. This flexibility enables the system to accurately control the response sensitivity of abnormal signals while maintaining the real-time generation of quantum random bits. Finally, real-time generation rate of 17.512 Gbit/s is attained with security parameters at the level of 10-50 and the generated random numbers passed NIST SP 800-22, Diehard, and TestU01 standard tests. This research provides a technical path for real-time assessment of entropy source security in QRNG. The proposed scheme has good integrability and scalability, presenting a feasible solution for QRNG to enter the application stage.

True random numbers are extracted through measurements of vacuum fluctuations in quantum state components. We propose an improved scheme utilizing an optimization-based simulation methodology to enhance the temporal resolution of quantum state detection and processing efficiency of vacuum fluctuation signals in continuous-variable quantum random number generators (CV-QRNGs), while simultaneously maximizing the entropy content of quantum noise sources. This work presents the first application of optimization simulation methodology to balanced homodyne detector (BHD) circuit design, with particular emphasis on improving high-frequency transmission characteristics. The design framework prioritizes system stability and S-parameter sensitivity to optimize both circuit architecture and critical component parameters. The AC amplifier circuit was implemented through ADS high-frequency simulations using two ABA-52563 RF amplifiers in a cascaded configuration, with circuit modeling performed on Rogers 4350 substrate optimized for high-frequency applications. This approach enabled the development of a switched-configuration BHD featuring: 1) 1.9 GHz bandwidth, 2) 41.5 dB signal-to-noise ratio at 1.75 GHz, 3) 30 dB common-mode rejection ratio at 100 MHz, and 4) frequency response flatness within 1.5 dB across 1.3-1.7 GHz. Additionally, the Husimi function is employed for entropy analysis to reconstruct vacuum state phase-space distributions, validating the detector's quantum measurement fidelity. The implemented system demonstrates a collective generation rate of 20.0504 Gbps across four parallel channels, with all output streams successfully passing NIST SP 800-22 statistical testing requirements.

Fiber fault detection based on the time-delay signature of an optical feedback semiconductor laser has the advantages of high sensitivity, precise location, and a simple structure, which make it widely applicable. The sensitivity of this method is determined by the feedback strength inducing the nonlinear state of the laser. This paper proposes a feedback compensation method to reduce the requirement of the fault echo intensity for the laser to enter the nonlinear state, significantly enhancing detection sensitivity. Numerical simulations analyze the impact of feedback compensation parameters on fault detection sensitivity and evaluate the performance of the laser operating at different pump currents. The results show that this method achieves a 9.33 dB improvement in sensitivity compared to the original approach, effectively addressing the challenges of detecting faults with high insertion losses in optical networks.

Wave-particle duality as a fundamental tenet of quantum mechanics is crucial for advancing comprehension of quantum theories and developing quantum technologies with practical applications. However, taking into account experimental impact factors to develop a feasible measurement for wave-like and particle-like properties of light fields is an ongoing challenge, and the non-classicality extraction and determination remains to be explored. In this work, feasibly measurable second-order photon correlations based on Hanbury Brown-Twiss and Hong-Ou-Mandel interferences are employed to analyze the evolution of wave-particle duality for various input states. The wave-particle dualities of chaotic, coherent and mixed classical states as functions of time delay and coherence time are investigated. The realistic impacts of background noise, detection efficiency, intensity ratio and phase differences on the wave-particle duality of nonclassical (Fock and squeezed coherent) states are unveiled. In noisy backgrounds with low detection efficiencies, efficient enhancement and extraction of non-classicality and a continuous transition from classical to nonclassical region are achieved in single photon state mixed with coherent state by adjusting the phase difference from 0 to pi/2. The non-classicality of squeezed coherent state can be induced by the classical wave-like and particle-like properties. The research provides a practical precision measurement of wave-particle duality that is helpful for the improvement of high-resolution quantum imaging and sensing.

Achieving high-fidelity acquisition and reconstruction of chaotic signals at a single-photon level remains a key challenge in secure communication and ultrasensitive sensing, primarily due to bandwidth and resolution limits of single-photon detectors (SPDs). In this work, we present an experimental method to recover high-bandwidth chaotic signals using low-bandwidth and high-sensitivity SPDs, which effectively mitigates the impacts of detector dead time and time jitter by shifting the signal spectrum into the SPD's response window and constructing a programmable gated sampling to time-stretch the signal. It achieves a maximum time stretching multiplication of 122 times, and the temporal resolution of SPD is improved by more than 24 times. For long-time high-precision sampling, a 16-channel FPGA-based time-to-digital conversion with a time resolution of 18.21 ps and a root mean square of 12.7 ps is self-developed to achieve high-efficiency single-photon signal acquisition by dynamically adjusting the sampling gate width. Single-gated time-stretch sampling of distorted single-photon signals achieves 95% fidelity experimentally. In time-interleaved gating sampling, parallel acquisition shortens the sampling time compared to single-gated sampling and captures transient variations of chaotic signals with 94% fidelity. Our method achieves an expansion of the effective sampling rate by over 100 times while maintaining the single-photon level sensitivity, providing an effective solution for ultrafast single-photon detection.

Standard weak measurement with an assistant pointer and single weak interaction constrains measurement precision and quantity of interaction parameters, and a compelling characterization of quantum effect featuring weak-value amplification (WVA) remains elusive. Here, we theoretically and experimentally demonstrate an enhanced dual-pointer WVA scheme based on multiple weak interactions and variable spectrum sources. Developing triple weak interactions, momentum P pointer reaches an optimal time-difference precision of 3.34 ×10^-5 as at 6 nm spectral width, and intensity I pointer achieves a displacement resolution of 148.8 fm within 400 kHz linewidth. A quantum effect associated with an anomalous weak value is revealed by an observable violation of a Leggett-Garg inequality. The I-pointer weak value is measured to be 1478 using multiple weak interactions and high signal-to-noise detection, achieving a two-order-of-magnitude WVA enhancement compared to standard weak measurement. Our work opens up a practical avenue for minuscule quantumness measurements in challenging environments.

As a universal-hashing function, Toeplitz hashing is migrated in QRNG from privacy amplification of QKD to execute information-theoretically provable true randomness extraction. Though random seed needed for constructing a Toeplitz matrix is longer than the output string, Toeplitz-hashing extractor is still much more favored in practical implementation of QRNG because its relative simple structure and parallel operation property compared to the other universal-hashing strong extractor, Trevisan's extractor, especially in the booming integration realization of randomness extractor via FPGA. But two origin issues have been put off for long in the random number post-processing in FPGA besides chasing speed: collision probability threaten owing to small matrix and security parameter growth due to seed reuse. In this work, seed update and collision probability are both paid close attention when realize real-time parallel post-processing of CV-QRNG, who has a pretty practical prospect as well as greatest demand on post-processing both because of whose wide detection bandwidth and multibit discretization. We propose a sub-seed generation scheme based on reading and writing between two levels of memories in FPGA, which effectively avoid the consumption of logic resources. One seeds pool is built in storage element of the FPGA and distinct random seed is chosen for each post-processing instance by a random selection process. And the seeds pool is swiftly updated via PCIe interface once security parameter reaches a pre-set threshold. Furthermore, by elaborate layout of Toeplitz matrixes and two-layer parallel pipeline algorithm with TDM designed delicately, four-channel parallel seed renewable Toeplitz post-processing with matrix of about 1700 x 2500 is realized with a real-time random number yield of 11.3 Gbps in one medium-configuration FPGA. In order to guarantee the robustness of the hardware-based parallel Toeplitz post-processing, timing is optimized by register replication, global clock buffers and data cache. This investigation fills an obvious hole in randomness extraction and provides a referential technique for privacy amplification.

Quantum systems are particularly suited for generating true randomness due to their inherent unpredictability, which can be justified on physical principles. However, practical implementations of Quantum RNGs (QRNGs) are always subject to noise, or uncontrollable influences, diminishing the quality of raw randomness produced. This necessitates post-processing to convert raw output into genuine randomness. In current QRNG implementations, the critical issue of seed updating is often overlooked, risking security vulnerabilities due to increased security parameters when seeds are reused in post-processing, and frequent seed updates fail to yield net randomness, while reusing seeds relies on the assumption that the original sequence inputs are independent.In this work, we have provided a specific scheme for seed updates that balances practicality and security, exploring the parallel and real-time implementation of multiple seed real-time updating toeplitz hash extractors in an FPGA to achieve parallel QRNGs, focusing on efficient hardware computation resource use. Through logic optimization, we achieved a greater number of parallel channels and a post-processing matrix size three times larger than previous works on the same FPGA platform, utilizing fewer logic resources. This resulted in a higher rate of random number generation and enhanced security. Furthermore, with the use of higher-performance ADCs, we attained a random number production rate exceeding 20Gbps.High-speed random number transfer and seed updating were achieved using the PCIe high-speed interface.This marks a significant step toward chip-based parallel QRNGs, enhancing the practicality of CV QRNGs in trusted, device-independent, and semi-device-independent scenarios.

This study presents a high-gain broadband balanced homodyne detector, utilizing cascade amplification to generate continuous-variable quantum random numbers. The innovative approach of distributed parameter circuit analysis and optimization simulation is introduced into the circuit design of the broadband balanced homodyne detector. The objective is to enhance the transmission attributes of the ultra-high-frequency circuit. This is realized by optimally combining different elements and selecting key electronic components, guided by system stability indicators. Hence, a balanced homodyne detector was developed with a bandwidth surpassing 1. 65 GHz and gain flatness of +/- 2 dB within the 0. 2-930 MHz range. This study proposes a novel design perspective for broadband balanced homodyne detectors. The enhanced features of the detectors facilitate a more efficient derivation of continuous-variable quantum state random entropy sources, thereby propelling the rate enhancement and practical advancement of continuous-variable quantum random number generators.

Continuous-variable quantum random number generators (CV-QRNGs) have promising application prospects thanks to their advantages such as high detection bandwidth, robustness of system, and integratability. In major CV-QRNGs, the generation of random numbers is based on homodyne detection and discretization of the quadrature fluctuations of the EM fields. Any defectiveness in physical realization may leak information correlated with the generated numbers and the maximal amount of randomness that can be extracted in presence of such side-information is evaluated by the so-called quantum conditional min-entropy. The parallel CV-QRNG overcomes the rate bottleneck of the previous serial type scheme. As a type of device-trusted QRNG, its security needs to be better guaranteed based on self-testing or monitoring that can be rigorously enforced. In this work, four sideband modes of vacuum state within 1.6 GHz detection bandwidth were extracted parallelly as the entropy source, and 16-bit analog-to-digital conversion in each channel was realized. Without making any ideal assumptions, the transfer function of the homodyne and quantization system was measured based on beat method to calibrate the evaluation of the min-entropy. Based on the rigorous entropy evaluation with a hash security parameter of εhash = 2−110, a real-time generation rate of 7.25 Gbps was finally achieved.