Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametr...Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.展开更多
In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodul...In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.展开更多
In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles we...In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature un-der a near-infrared photo source （980 nm） and UV-vis photo source, respectively.The results indicated thatα-TeO2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence. Theα-TeO2：Ho3＋/Yb3＋nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation, ascribed to the5S2→5I8 and5F5→5I8（Ho3＋） transitions, and weaker down-conversion emission at 545 nm under 455 nm excitation, ascribed to the5S2→5I8（Ho3＋） transitions. Theα-TeO2：Eu3＋nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation, attributed to the5D0→7F1 and 5D0→7F2 （Eu3＋） transitions. Possessing the advantages of these two luminescent materials, the as-prepared tri-doped samples ofα-TeO2：0.5Ho3＋/10Yb3＋/3Eu3＋ （mol.%）nanoparticles could successfully emit visible light via both up- and down-conversion modes.展开更多
Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single ph...Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single In As quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate（PPLN） waveguide and a 1.95 μmm pump laser, and the frequency conversion efficiency is ~40%. The singlephoton purity of quantum dot emission is preserved during the down-conversion process, i.e., g^（（2））（0）, only 0.22 at 1552 nm.This present technique advances the Ⅲ-Ⅴ semiconductor quantum dots as a promising platform for long-distance quantum communication.展开更多
We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variati...We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and splitting.We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth.Our study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.展开更多
We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achiev...We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achieved under typical dissipation conditions.To obtain a transparent understanding of the relevant physical process,we show that in the large detuned case,the cavity can be eliminated adiabatically,resulting in a parametric down-conversion(PDC)interaction between two phononic polariton modes.By tuning cavity detuning,the nonlinear interaction can be enhanced with the frequency-matching condition.Results from analytical treatment based on the effective PDC model agree with the numerical simulation.Such a system provides potential applications in nonlinear phononics.展开更多
By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the dege...By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.展开更多
A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- ti...A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.展开更多
Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties ...Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.展开更多
针对中波广播信号监测需求,提出基于软件定义无线电(Software Defined Radio,SDR)技术的中波广播信号监测系统优化设计方案。通过构建通用化硬件平台与可编程软件架构,结合分布式信号采集网络和多节点联合定位算法,系统实现了对中波广...针对中波广播信号监测需求,提出基于软件定义无线电(Software Defined Radio,SDR)技术的中波广播信号监测系统优化设计方案。通过构建通用化硬件平台与可编程软件架构,结合分布式信号采集网络和多节点联合定位算法,系统实现了对中波广播信号的实时监测与异常定位。监测方案通过部署探针设备组网采集电磁特征数据,结合云计算与虚拟化技术优化后台数据处理能力,并建立了异常告警机制与高可用数据库系统。实验结果表明,系统具备快速响应、高准确率及稳定运行的特性,可满足复杂环境下的中波广播信号监测需求。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 62075010)。
文摘Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.
文摘In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.
基金supported by the National Natural Science Foundation of China(21075053)the"Challenge Cup"Undergraduate Extra-curriculum Academics,Science and Technology Works Competition and Student's Platform for Innovation and Entrepreneurship Training Program(201410559056)in Jinan University
文摘In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature un-der a near-infrared photo source （980 nm） and UV-vis photo source, respectively.The results indicated thatα-TeO2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence. Theα-TeO2：Ho3＋/Yb3＋nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation, ascribed to the5S2→5I8 and5F5→5I8（Ho3＋） transitions, and weaker down-conversion emission at 545 nm under 455 nm excitation, ascribed to the5S2→5I8（Ho3＋） transitions. Theα-TeO2：Eu3＋nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation, attributed to the5D0→7F1 and 5D0→7F2 （Eu3＋） transitions. Possessing the advantages of these two luminescent materials, the as-prepared tri-doped samples ofα-TeO2：0.5Ho3＋/10Yb3＋/3Eu3＋ （mol.%）nanoparticles could successfully emit visible light via both up- and down-conversion modes.
基金Project supported by the National Key Technologies R&D Program of China(Grant No.2018YFA0306101)the Scientific Instrument Developing Project of Chinese Academy of Sciences(Grant No.YJKYYQ20170032)the National Natural Science Foundation of China(Grant No.61505196)
文摘Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single In As quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate（PPLN） waveguide and a 1.95 μmm pump laser, and the frequency conversion efficiency is ~40%. The singlephoton purity of quantum dot emission is preserved during the down-conversion process, i.e., g^（（2））（0）, only 0.22 at 1552 nm.This present technique advances the Ⅲ-Ⅴ semiconductor quantum dots as a promising platform for long-distance quantum communication.
基金Project supported by the National Key R&D Program of China(Grant No.2019YFA0705000)Leading-edge Technology Program of Jiangsu Natural Science Foundation,China(Grant No.BK20192001)the National Natural Science Foundation of China(Grant Nos.51890861,11690031,11974178,and 11627810).
文摘We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and splitting.We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth.Our study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.
基金support from the NSFC(Grant No.12275331)the Penghuanwu Innovative Research Center(Grant No.12047503)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD031602)。
文摘We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achieved under typical dissipation conditions.To obtain a transparent understanding of the relevant physical process,we show that in the large detuned case,the cavity can be eliminated adiabatically,resulting in a parametric down-conversion(PDC)interaction between two phononic polariton modes.By tuning cavity detuning,the nonlinear interaction can be enhanced with the frequency-matching condition.Results from analytical treatment based on the effective PDC model agree with the numerical simulation.Such a system provides potential applications in nonlinear phononics.
基金supported by the National Natural Science Foundation of China under Grant Nos.40674076 and 40474064the Hunan Natural Science Foundation of China under Grant No.07JJ3123the Scientific Research Fund of Hunan Provincial Education Department under Grant Nos.06C163,05B023,and 06B004
文摘By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.
基金Supported by the National Key Basic Research Program of China under Grant Nos 2013CB933304 and 2014CB643904the National Natural Science Foundation of China under Grant Nos 61435012 and 61274125the Strategic Priority Research Program(B) of Chinese Academy of Sciences under Grant No XDB01010200
文摘A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.
基金Project supported by the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB01030100 and XDB01030300)the National Key Research and Development Program of China(Grant No.2016YFA0302600)the National Natural Science Foundation of China(Grant Nos.61475148 and 61575183)
文摘Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.
文摘针对中波广播信号监测需求,提出基于软件定义无线电(Software Defined Radio,SDR)技术的中波广播信号监测系统优化设计方案。通过构建通用化硬件平台与可编程软件架构,结合分布式信号采集网络和多节点联合定位算法,系统实现了对中波广播信号的实时监测与异常定位。监测方案通过部署探针设备组网采集电磁特征数据,结合云计算与虚拟化技术优化后台数据处理能力,并建立了异常告警机制与高可用数据库系统。实验结果表明,系统具备快速响应、高准确率及稳定运行的特性,可满足复杂环境下的中波广播信号监测需求。
