In this paper, we report our recent experiment of long-distance fiber-optic plug and play quantum cryptography system wherein a Faraday-Mirror was used to compensate for the polarization mode dispersion and phase drif...In this paper, we report our recent experiment of long-distance fiber-optic plug and play quantum cryptography system wherein a Faraday-Mirror was used to compensate for the polarization mode dispersion and phase drifts. The pulse-biased coincident gate single-photon detection technique was used to effectively reduce the noises from the detrimental Rayleigh backscattering. We have achieved a quantum key distribution system with the working distance of 50 km, which was tested to be stable in more than 6 hours continuous work. And we also demonstrated the practical quantum communication in a local area network using the TCP protocol.展开更多
The nonlocal emitter-waveguide coupling,which gives birth to the so called giant atom,represents a new paradigm in the field of quantum optics and waveguide QED.We investigate the single-photon scattering in a one-dim...The nonlocal emitter-waveguide coupling,which gives birth to the so called giant atom,represents a new paradigm in the field of quantum optics and waveguide QED.We investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom.Thanks to the natural interference induced by the back and forth photon transmitted/reflected between the atomwaveguide coupling points,the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom.For the two-level giant-atom setup,we demonstrate the energy shift which is dependent on the atomic size.For the driven three-level giantatom setup,it is of great interest that,the Autler–Townes splitting is dramatically modulated by the giant atom,in which the width of the transmission valleys(reflection range)is tunable in terms of the atomic size.Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.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
Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local...Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.展开更多
基金supported by the Shanghai Priority Academic Discipline,the National Natural Science Foundation of China(Grant No.10374028)the National Fundamental Research Program of China(Grant No.001CB309301).
文摘In this paper, we report our recent experiment of long-distance fiber-optic plug and play quantum cryptography system wherein a Faraday-Mirror was used to compensate for the polarization mode dispersion and phase drifts. The pulse-biased coincident gate single-photon detection technique was used to effectively reduce the noises from the detrimental Rayleigh backscattering. We have achieved a quantum key distribution system with the working distance of 50 km, which was tested to be stable in more than 6 hours continuous work. And we also demonstrated the practical quantum communication in a local area network using the TCP protocol.
文摘The nonlocal emitter-waveguide coupling,which gives birth to the so called giant atom,represents a new paradigm in the field of quantum optics and waveguide QED.We investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom.Thanks to the natural interference induced by the back and forth photon transmitted/reflected between the atomwaveguide coupling points,the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom.For the two-level giant-atom setup,we demonstrate the energy shift which is dependent on the atomic size.For the driven three-level giantatom setup,it is of great interest that,the Autler–Townes splitting is dramatically modulated by the giant atom,in which the width of the transmission valleys(reflection range)is tunable in terms of the atomic size.Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.
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Project supported by the National Special Fund for Major Research Instrument Development of China(Grant No.11527808)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11504262)+2 种基金the National Basic Research Program of China(Grant No.2014CB340103)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120032110055)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.14JCQNJC02300)
文摘Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.
