In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. （QD） which a.re necessary to the nnderstanding of the physics of single-photon generation...In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. （QD） which a.re necessary to the nnderstanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantmn emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as opti- cal properties of the QDs. We then review the localizatioll of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and perfornances in terms of strong coupling regime, elfieiency, directionality, and polarization control. Furthermore, we will discuss the recenl, progress on the fabrication of single photon sources, and various a.pproaehes for embedding single QDs into mieroca,vities or photonic crystal nanoeavities and show how to ex- tend the wavelength range. We focus in part;icular on new generations of electrically driven QD single photon source leading to high repetition rates, efficiencies at elevated temperature operation. Besides strong eoupling regime, and high collection new development;s of room temperature sin- gle photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for pract ical single-photon sources are also discussed.展开更多
Neural networks are becoming ubiquitous in various areas of physics as a successful machine learning(ML)technique for addressing different tasks.Based on ML technique,we propose and experimentally demonstrate an effic...Neural networks are becoming ubiquitous in various areas of physics as a successful machine learning(ML)technique for addressing different tasks.Based on ML technique,we propose and experimentally demonstrate an efficient method for state reconstruction of the widely used Sagnac polarization-entangled photon source.By properly modeling the target states,a multi-output fully connected neural network is well trained using only six of the sixteen measurement bases in standard tomography technique,and hence our method reduces the resource consumption without loss of accuracy.We demonstrate the ability of the neural network to predict state parameters with a high precision by using both simulated and experimental data.Explicitly,the mean absolute error for all the parameters is below 0.05 for the simulated data and a mean fidelity of 0.99 is achieved for experimentally generated states.Our method could be generalized to estimate other kinds of states,as well as other quantum information tasks.展开更多
The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated.The fluorescence lifetime,blinking phenomenon,and anti-bunching effect of a single CdTeSe/ZnS quantum...The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated.The fluorescence lifetime,blinking phenomenon,and anti-bunching effect of a single CdTeSe/ZnS quantum dot with an emission wavelength of 800 nm at room temperature are studied.The second-order correlation function at zero delay time is much smaller than 0.1,which proves that the emission from single quantum dots at 800 nm is a highly pure single-photon source.The effects of the irradiation duration on the fluorescence from single quantum dots are analyzed.The experimental results can be explained by a recombination model including a multi-nonradiative recombination center model and a multi-charged model.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
Quantum emitters are widely used in quantum networks,quantum information processing,and quantum sensing due to their excellent optical properties.Compared with Stokes excitation,quantum emitters under anti-Stokes exci...Quantum emitters are widely used in quantum networks,quantum information processing,and quantum sensing due to their excellent optical properties.Compared with Stokes excitation,quantum emitters under anti-Stokes excitation exhibit better performance.In addition to laser cooling and nanoscale thermometry,anti-Stokes excitation can improve the coherence of single-photon sources for advanced quantum technologies.In this review,we follow the recent advances in phononassisted upconversion photoluminescence of quantum emitters and discuss the upconversion mechanisms,applications,and prospects for quantum emitters with anti-Stokes excitation.展开更多
Epitaxial quantum dots formed by III–V compound semiconductors are excellent sources of nonclassical photons,creating single photons and entangled multi-photon states on demand.Their semiconductor nature allows for a...Epitaxial quantum dots formed by III–V compound semiconductors are excellent sources of nonclassical photons,creating single photons and entangled multi-photon states on demand.Their semiconductor nature allows for a straightforward combination with mature integrated photonic technologies,leading to novel functional devices at the single-photon level.Integrating a quantum dot into a carefully engineered photonic cavity enables control of the radiative decay rate using the Purcell effect and the realization of photon–photon nonlinear gates.In this review,we introduce the basis of epitaxial quantum dots and discuss their applications as non-classical light sources.We highlight two interfaces—one between flying photons and the quantum-dot dipole,and the other between the photons and the spin.We summarize the recent development of integrated photonics and reconfigurable devices that have been combined with quantum dots or are suitable for hybrid integration.Finally,we provide an outlook of employing quantum-dot platforms for practical applications in large-scale quantum computation and the quantum Internet.展开更多
We have investigated the optical properties of single CdSe/ZnS nanocrystals by conducting combinations of experiments on antibunching and photoluminescence intermittence under different experimental conditions.Based o...We have investigated the optical properties of single CdSe/ZnS nanocrystals by conducting combinations of experiments on antibunching and photoluminescence intermittence under different experimental conditions.Based on photoluminescence in an antibunching experiment,we analyzed the emission lifetime of QDs by using stretched exponentials.The difference between the parameters obtained from average lifetimes and stretched exponents were analyzed by considering the effect of nonradiative emission.An Auger-assisted tunneling model was used to explain the power law exponents of off time distribution.The power law exponent under high excitation power was correlated with a higher Auger ionization rate.Using the parameters obtained from stretched exponential function and power law,the antibunching phenomena at different time and under different excitation intensity were analyzed.展开更多
基金G. Shan would like to thank Prof. C. Cohen-Tannoudji （Nobel Laureate in 1997） for his fruitful discus- sion on quantum optics and particularly theory of quantum-dot- cavity during his visit at City University of Hong Kong in 2012. This work was partially sponsored by General Research Grant Project No. CityU 119212 from RGC, Hong Kong, and the re- search activity fund from CityU to support research work as a visiting scholar at Columbia University. W. Huang acknowledges the support from the National Basic Research Program of China （973 Program, Grant No. 2009CB930601）. Z. Yin acknowledges the support by the National Basic Research Program of China （973 Program, Grant Nos. 2011CBA00300 and 2011CBA00302）, and the National Natural Science Foundation of China （Grant Nos. 61033001 and 11105136）.
文摘In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. （QD） which a.re necessary to the nnderstanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantmn emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as opti- cal properties of the QDs. We then review the localizatioll of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and perfornances in terms of strong coupling regime, elfieiency, directionality, and polarization control. Furthermore, we will discuss the recenl, progress on the fabrication of single photon sources, and various a.pproaehes for embedding single QDs into mieroca,vities or photonic crystal nanoeavities and show how to ex- tend the wavelength range. We focus in part;icular on new generations of electrically driven QD single photon source leading to high repetition rates, efficiencies at elevated temperature operation. Besides strong eoupling regime, and high collection new development;s of room temperature sin- gle photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for pract ical single-photon sources are also discussed.
基金the financial support from the National Natural Science Foundation of China(11774326)the National Key R&D Program of China(2017YFA0304301)+2 种基金Innovation Program for Quantum Science and Technology(2021ZD0300204)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Anhui Initiative in Quantum Information Technologies。
基金Project supported by the National Key Research and Development Program of China (Grant No.2019YFA0705000)Leading-edge technology Program of Jiangsu Natural Science Foundation (Grant No.BK20192001)the National Natural Science Foundation of China (Grant No.11974178)。
文摘Neural networks are becoming ubiquitous in various areas of physics as a successful machine learning(ML)technique for addressing different tasks.Based on ML technique,we propose and experimentally demonstrate an efficient method for state reconstruction of the widely used Sagnac polarization-entangled photon source.By properly modeling the target states,a multi-output fully connected neural network is well trained using only six of the sixteen measurement bases in standard tomography technique,and hence our method reduces the resource consumption without loss of accuracy.We demonstrate the ability of the neural network to predict state parameters with a high precision by using both simulated and experimental data.Explicitly,the mean absolute error for all the parameters is below 0.05 for the simulated data and a mean fidelity of 0.99 is achieved for experimentally generated states.Our method could be generalized to estimate other kinds of states,as well as other quantum information tasks.
基金Project supported by the National Natural Science Foundation of China(Grant No.92165202)the Innovation Program for Quantum Science and Technology,China(Grant No.2021ZD0300701)the Strategic Priority Research Program(A)of Chinese Academy of Sciences(Grant No.XDA18040300).
文摘The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated.The fluorescence lifetime,blinking phenomenon,and anti-bunching effect of a single CdTeSe/ZnS quantum dot with an emission wavelength of 800 nm at room temperature are studied.The second-order correlation function at zero delay time is much smaller than 0.1,which proves that the emission from single quantum dots at 800 nm is a highly pure single-photon source.The effects of the irradiation duration on the fluorescence from single quantum dots are analyzed.The experimental results can be explained by a recombination model including a multi-nonradiative recombination center model and a multi-charged model.
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the National Key Research and Development Program of China(2017YFA0303401)the CAS Interdisciplinary Innovation Team,the Strategic Priority Research Program of Chinese Academy of Sciences(grant no.XDB28000000)the NSFC(12074371,U21A2070,and 62027816)。
文摘Quantum emitters are widely used in quantum networks,quantum information processing,and quantum sensing due to their excellent optical properties.Compared with Stokes excitation,quantum emitters under anti-Stokes excitation exhibit better performance.In addition to laser cooling and nanoscale thermometry,anti-Stokes excitation can improve the coherence of single-photon sources for advanced quantum technologies.In this review,we follow the recent advances in phononassisted upconversion photoluminescence of quantum emitters and discuss the upconversion mechanisms,applications,and prospects for quantum emitters with anti-Stokes excitation.
基金the National Natural Science Foundation of China(NSFC)(62005195)L.Z.acknowledges support from NCCR QSIT and SNF project(200020_204069)J.L.acknowledges support from the National Key R&D Program of China(2018YFA0306100).
文摘Epitaxial quantum dots formed by III–V compound semiconductors are excellent sources of nonclassical photons,creating single photons and entangled multi-photon states on demand.Their semiconductor nature allows for a straightforward combination with mature integrated photonic technologies,leading to novel functional devices at the single-photon level.Integrating a quantum dot into a carefully engineered photonic cavity enables control of the radiative decay rate using the Purcell effect and the realization of photon–photon nonlinear gates.In this review,we introduce the basis of epitaxial quantum dots and discuss their applications as non-classical light sources.We highlight two interfaces—one between flying photons and the quantum-dot dipole,and the other between the photons and the spin.We summarize the recent development of integrated photonics and reconfigurable devices that have been combined with quantum dots or are suitable for hybrid integration.Finally,we provide an outlook of employing quantum-dot platforms for practical applications in large-scale quantum computation and the quantum Internet.
基金supported by the National Natural Science Foundation of China (Grant No 60877030)National High Technology Research and Development Program of China (Grant No 2009AA03Z406)Grant-in-Aid for Scientific Research (C) (Grant No 20510112)
文摘We have investigated the optical properties of single CdSe/ZnS nanocrystals by conducting combinations of experiments on antibunching and photoluminescence intermittence under different experimental conditions.Based on photoluminescence in an antibunching experiment,we analyzed the emission lifetime of QDs by using stretched exponentials.The difference between the parameters obtained from average lifetimes and stretched exponents were analyzed by considering the effect of nonradiative emission.An Auger-assisted tunneling model was used to explain the power law exponents of off time distribution.The power law exponent under high excitation power was correlated with a higher Auger ionization rate.Using the parameters obtained from stretched exponential function and power law,the antibunching phenomena at different time and under different excitation intensity were analyzed.
