The 1.55-μm quantum-dot (QD) micropillar cavities are strongly required as single photon sources (SPSs) for silica-fiber-based quantum information processing. Theoretical analysis shows that the adiabatic distributed...The 1.55-μm quantum-dot (QD) micropillar cavities are strongly required as single photon sources (SPSs) for silica-fiber-based quantum information processing. Theoretical analysis shows that the adiabatic distributed Bragg reflector (DBR) structure may greatly improve the quality of a micropillar cavity. An InGaAsP/InP micropillar cavity is originally difficult, but it becomes more likely usable with inserted tapered (thickness decreased towards the center) distributed DBRs. Simulation turns out that, incorporating adiabatically tapered DBRs, a Si/SiO2- InP hybrid micropillar cavity, which enables weakly coupling InAs/InP quantum dots (QDs), can even well satisfy strong coupling at a smaller diameter. Certainly, not only the tapered structure, other adiabatic designs, e.g., both DBR layers getting thicker and one thicker one thinner, also improve the quality, reduce the diameter, and degrade the fabrication difficulty of Si/SiO2-InP hybrid micropillar cavities. Furthermore, the problem of the thin epitaxial semiconductor layer can also be greatly resolved by inserting adiabatic InGaAsP/InP DBRs. With tapered DBRs, the InGaAsP/InP-air-aperture micro-pillar cavity serves as an efficient, coherent, and monolithically producible 1.55-μm single-photon source (SPS). The adiabatic design is thus an effective way to obtain prospective candidates for 1.55-μm QD SPSs.展开更多
Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum...Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum component in a weak coherent pulses source, we employ a practical decoy-state scheme with heralded singlephoton source for the RRDPS protocol and analyze the performance of this method. In this scheme, only two decoy states are needed and the yields of single-photon state and multi-photon states, as well as the bit error rates of each photon states, can be estimated. The final key rate of this scheme is bounded and simulated over transmission distance. The results show that the two-decoy-state method with heralded single-photon source performs better than the two-decoy-state method with weak coherent pulses.展开更多
Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devi...Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.展开更多
Reference-frame-independent（RFI）quantum key distribution（QKD）is a protocol which can share unconditional secret keys between two remote users without the alignment of slowly varying reference frames.We propose a p...Reference-frame-independent（RFI）quantum key distribution（QKD）is a protocol which can share unconditional secret keys between two remote users without the alignment of slowly varying reference frames.We propose a passive decoy-state RFI-QKD protocol with heralded single-photon source（HSPS）and present its security analysis.Compared with RFI QKD using a weak coherent pulse source（WCPS）,numerical simulations show that the passive decoy-state RFI QKD with HSPS performs better not only in secret key rate but also in secure transmission distance.Moreover,our protocol is robust against the relative motion of the reference frames as well as RFI QKD with the WCPS.In addition,we also exploit Hoeffding＇s inequality to investigate the finite-key effect on the security of the protocol.展开更多
Single-photon flux is one of the crucial properties of nitrogen vacancy （NV） centers in diamond for its application in quantum information techniques. Here we fabricate diamond conical nanowires to enhance the singl...Single-photon flux is one of the crucial properties of nitrogen vacancy （NV） centers in diamond for its application in quantum information techniques. Here we fabricate diamond conical nanowires to enhance the single-photon count rate. Through the interaction between tightly confined optical mode in nanowires and NV centers, the single-photon lifetime is much shortened and the collection efficiency is enhanced. As a result, the detected single-photon rate can be at 564 kcps, and the total detection coefficient can be 0.8%, which is much higher than that in bulk diamond. Such a nanowire single-photon device with high photon flux can be applied to improve the fidelity of quantum computation and the precision of quantum sensors.展开更多
On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from...On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from multi-photon problem brought from photon splitter number attacks.On the other hand,the orbital angular momentum(OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame,solving the dependency of the base in the MDI-QKD protocol.Given that,we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent(SPACS)and heralded single-photon sources(HSPS).Due to the stability of OAM and the participation of parametric light sources,the performance of MDI-QKD protocol gradually approaches the ideal situation.Numerical simulation shows that compared with WCP scheme,HSPS and SPACS schemes have increased the maximum secure transmission distance by 30 km and 40 km respectively.展开更多
针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transiti...针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transition field,MTF)与深度确定性策略梯度算法(deep deterministic policy gradient,DDPG)结合的鲁棒性强、不依赖电路参数特性以及可视化的VSC-HVDC控制参数优化设计方法。首先,采用马尔科夫转换场将电路功率、电压等一维时序波形数据转换为二维马尔科夫转换场域图像并使用马尔科夫转换场损失函数(Markov transition field loss,MTFL)判断二维转换域图的数据波动性;其次,将MTFL损失函数与DDPG算法相结合,综合利用MTFL损失函数对系统输出时序数据动态特性评价能力更强的优点和DDPG算法泛化性能优秀的特点,实现VSC-HVDC系统控制参数优化;最后,通过MATLAB模拟和实验结果验证该方法的有效性。展开更多
In this work,we achieve high count-rate single-photon output in single-mode(SM)optical fiber.Epitaxial and dilute InAs/GaAs quantum dots(QDs)are embedded in a GaAs/AlGaAs distributed Bragg reflector(DBR)with a micro-p...In this work,we achieve high count-rate single-photon output in single-mode(SM)optical fiber.Epitaxial and dilute InAs/GaAs quantum dots(QDs)are embedded in a GaAs/AlGaAs distributed Bragg reflector(DBR)with a micro-pillar cavity,so as to improve their light emission extraction in the vertical direction,thereby enhancing the optical SM fiber’s collection capabil-ity(numerical aperture:0.13).By tuning the temperature precisely to make the quantum dot exciton emission resonant to the micro-pillar cavity mode(Q~1800),we achieve a fiber-output single-photon count rate as high as 4.73×10^(6) counts per second,with the second-order auto-correlation g2(0)remaining at 0.08.展开更多
In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with ...In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with Purcell enhancement),interconnectivity with spin qubits,and a scalable on-chip platform.However,in the past two decades,the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%,and the distances were limited from a few meters to kilometers.Here,we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber.The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities.Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band.The observed interference visibility is 0.670.02(0.930.04)without(with)temporal filtering.Feasible improvements can further extend the distance to∼600 km.Our work represents a key step to long-distance solid-state quantum networks.展开更多
A single-photon source with narrow bandwidth,high purity,and large brightness can efficiently interact with material qubits strongly coupled to an optical microcavity for quantum information processing.Here,we experim...A single-photon source with narrow bandwidth,high purity,and large brightness can efficiently interact with material qubits strongly coupled to an optical microcavity for quantum information processing.Here,we experimentally demonstrate a degenerate doubly resonant single-photon source at 852 nm by the cavity-enhanced spontaneous parametric downconversion process with a 100%duty cycle of generation.The single photon source possesses both high purity with a second-order correlation g^((2))_(h)(0)=0.021 and narrow linewidth with△_(V_(sp))=(800±13)kHz.The single-photon s Single-photon source with sub-MHz linewidth for cesium-based quantum information processingource is compatible with the cesium atom D2 line and can be used for cesium-based quantum information processing Single-photon source with sub-MHz linewidth for cesium-based quantum information processing0.021.展开更多
基金supported by the Sichuan Science and Technology Program under Grant No.2018JY0084
文摘The 1.55-μm quantum-dot (QD) micropillar cavities are strongly required as single photon sources (SPSs) for silica-fiber-based quantum information processing. Theoretical analysis shows that the adiabatic distributed Bragg reflector (DBR) structure may greatly improve the quality of a micropillar cavity. An InGaAsP/InP micropillar cavity is originally difficult, but it becomes more likely usable with inserted tapered (thickness decreased towards the center) distributed DBRs. Simulation turns out that, incorporating adiabatically tapered DBRs, a Si/SiO2- InP hybrid micropillar cavity, which enables weakly coupling InAs/InP quantum dots (QDs), can even well satisfy strong coupling at a smaller diameter. Certainly, not only the tapered structure, other adiabatic designs, e.g., both DBR layers getting thicker and one thicker one thinner, also improve the quality, reduce the diameter, and degrade the fabrication difficulty of Si/SiO2-InP hybrid micropillar cavities. Furthermore, the problem of the thin epitaxial semiconductor layer can also be greatly resolved by inserting adiabatic InGaAsP/InP DBRs. With tapered DBRs, the InGaAsP/InP-air-aperture micro-pillar cavity serves as an efficient, coherent, and monolithically producible 1.55-μm single-photon source (SPS). The adiabatic design is thus an effective way to obtain prospective candidates for 1.55-μm QD SPSs.
基金Supported by the National Basic Research Program of China under Grant No 2013CB338002the National Natural Science Foundation of China under Grant Nos 11304397 and 61505261
文摘Round-robin differential phase shift （RRDPS） is a novel quantum key distribution protocol which can bound information leakage without monitoring signal disturbance. In this work, to decrease the effect of the vacuum component in a weak coherent pulses source, we employ a practical decoy-state scheme with heralded singlephoton source for the RRDPS protocol and analyze the performance of this method. In this scheme, only two decoy states are needed and the yields of single-photon state and multi-photon states, as well as the bit error rates of each photon states, can be estimated. The final key rate of this scheme is bounded and simulated over transmission distance. The results show that the two-decoy-state method with heralded single-photon source performs better than the two-decoy-state method with weak coherent pulses.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074194,12104240,and 62101285)the Industrial Prospect and Key Core Technology Projects of Jiangsu Provincial Key Research and Development Program(Grant No.BE2022071)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20192001 and BK20210582).
文摘Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.
基金Supported by the National Basic Research Program of China under Grant No 2013CB338002the National Natural Science Foundation of China under Grant Nos 61505261,61675235,61605248 and 11304397
文摘Reference-frame-independent（RFI）quantum key distribution（QKD）is a protocol which can share unconditional secret keys between two remote users without the alignment of slowly varying reference frames.We propose a passive decoy-state RFI-QKD protocol with heralded single-photon source（HSPS）and present its security analysis.Compared with RFI QKD using a weak coherent pulse source（WCPS）,numerical simulations show that the passive decoy-state RFI QKD with HSPS performs better not only in secret key rate but also in secure transmission distance.Moreover,our protocol is robust against the relative motion of the reference frames as well as RFI QKD with the WCPS.In addition,we also exploit Hoeffding＇s inequality to investigate the finite-key effect on the security of the protocol.
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFA0304504the National Natural Science Foundation of China under Grant Nos 11374290,61522508,91536219 and 11504363
文摘Single-photon flux is one of the crucial properties of nitrogen vacancy （NV） centers in diamond for its application in quantum information techniques. Here we fabricate diamond conical nanowires to enhance the single-photon count rate. Through the interaction between tightly confined optical mode in nanowires and NV centers, the single-photon lifetime is much shortened and the collection efficiency is enhanced. As a result, the detected single-photon rate can be at 564 kcps, and the total detection coefficient can be 0.8%, which is much higher than that in bulk diamond. Such a nanowire single-photon device with high photon flux can be applied to improve the fidelity of quantum computation and the precision of quantum sensors.
基金Hong Lai has been supported by the National Natural Science Foundation of China(No.61702427)the Chongqing innovation project(No.cx2018076)+1 种基金the Fundamental Research Funds for the Central Universities(XDJK2018C048)the financial support in part by the 1000-Plan of Chongqing by Southwest University(No.SWU116007)。
文摘On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from multi-photon problem brought from photon splitter number attacks.On the other hand,the orbital angular momentum(OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame,solving the dependency of the base in the MDI-QKD protocol.Given that,we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent(SPACS)and heralded single-photon sources(HSPS).Due to the stability of OAM and the participation of parametric light sources,the performance of MDI-QKD protocol gradually approaches the ideal situation.Numerical simulation shows that compared with WCP scheme,HSPS and SPACS schemes have increased the maximum secure transmission distance by 30 km and 40 km respectively.
文摘针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transition field,MTF)与深度确定性策略梯度算法(deep deterministic policy gradient,DDPG)结合的鲁棒性强、不依赖电路参数特性以及可视化的VSC-HVDC控制参数优化设计方法。首先,采用马尔科夫转换场将电路功率、电压等一维时序波形数据转换为二维马尔科夫转换场域图像并使用马尔科夫转换场损失函数(Markov transition field loss,MTFL)判断二维转换域图的数据波动性;其次,将MTFL损失函数与DDPG算法相结合,综合利用MTFL损失函数对系统输出时序数据动态特性评价能力更强的优点和DDPG算法泛化性能优秀的特点,实现VSC-HVDC系统控制参数优化;最后,通过MATLAB模拟和实验结果验证该方法的有效性。
基金supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2018B030329001)the National Key Technologies R&D Program of China(2018YFA0306101)+2 种基金The Scientific Instrument Developing Project of the Chinese Academy of Science(YJKYYQ20170032)the National Natural Science Foundation of China(61505196)the Program of Beijing Academy of Quantum Information Sciences(Grant No.Y18G01).
文摘In this work,we achieve high count-rate single-photon output in single-mode(SM)optical fiber.Epitaxial and dilute InAs/GaAs quantum dots(QDs)are embedded in a GaAs/AlGaAs distributed Bragg reflector(DBR)with a micro-pillar cavity,so as to improve their light emission extraction in the vertical direction,thereby enhancing the optical SM fiber’s collection capabil-ity(numerical aperture:0.13).By tuning the temperature precisely to make the quantum dot exciton emission resonant to the micro-pillar cavity mode(Q~1800),we achieve a fiber-output single-photon count rate as high as 4.73×10^(6) counts per second,with the second-order auto-correlation g2(0)remaining at 0.08.
基金the National Natural Science Foundation of China(91836303)the National Key R&D Program of China(2019YFA0308700)+1 种基金the Chinese Academy of Sciences,the Anhui Initiative in Quantum Information Technologies,the Natural Science Foundation of Shandong Province(ZR2020LLZ007)the ShanghaiMunicipal Science and Technology Major Project(2019SHZDZX01).
文摘In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with Purcell enhancement),interconnectivity with spin qubits,and a scalable on-chip platform.However,in the past two decades,the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%,and the distances were limited from a few meters to kilometers.Here,we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber.The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities.Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band.The observed interference visibility is 0.670.02(0.930.04)without(with)temporal filtering.Feasible improvements can further extend the distance to∼600 km.Our work represents a key step to long-distance solid-state quantum networks.
基金supported by the National Natural Science Foundation of China (Grant Nos.11974223,and 11974225)the Fund for Shanxi 1331 Project Key Subjects Construction.
文摘A single-photon source with narrow bandwidth,high purity,and large brightness can efficiently interact with material qubits strongly coupled to an optical microcavity for quantum information processing.Here,we experimentally demonstrate a degenerate doubly resonant single-photon source at 852 nm by the cavity-enhanced spontaneous parametric downconversion process with a 100%duty cycle of generation.The single photon source possesses both high purity with a second-order correlation g^((2))_(h)(0)=0.021 and narrow linewidth with△_(V_(sp))=(800±13)kHz.The single-photon s Single-photon source with sub-MHz linewidth for cesium-based quantum information processingource is compatible with the cesium atom D2 line and can be used for cesium-based quantum information processing Single-photon source with sub-MHz linewidth for cesium-based quantum information processing0.021.
