We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Tw...We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Two factors that result in the excess noises of the quantum key distribution system are analyzed.The first is the relative phase dithering between the signal and local fields,and the second is the local field leakage into the signal field due to the scattering process that depolarizes the local field.It is found that the latter has a significant impact on the excess noise,which is the main limiting factor to the long-distance secure quantum transmission.Some protocols are also given to decrease the excess noise effectively.展开更多
We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser.The highest output power of 280 mW at 461.62 nm is obtained by employing a type-I phase-matched BIBO crystal an...We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser.The highest output power of 280 mW at 461.62 nm is obtained by employing a type-I phase-matched BIBO crystal and the peak-to-peak fluctuation of the power is less than±1%within three hours.The frequency stability is better than±2.22 MHz over 10 min when the laser is locked to a confocal Fabry–Perot cavity.A three-plate birefringent filter allows for the tunable range from 457 nm to 467 nm,which covers the absorption line of the strontium atoms(460.86 nm).展开更多
We present an ultrastable fiber-based time-domain balanced homodyne detector which can be used for precise characterization of pulsed quantum light fields.A variable optical attenuator based on bending the fiber is ut...We present an ultrastable fiber-based time-domain balanced homodyne detector which can be used for precise characterization of pulsed quantum light fields.A variable optical attenuator based on bending the fiber is utilized to compensate for the different quantum efficiencies of the photodiodes precisely,and a common mode rejection ratio of above 76 dB is achieved.The detector has a gain of 3.2μV per photon and a signal-to-noise ratio above 20 dB.Optical pulses with repetition rates up to 2 MHz can be measured with a detection efficiency of 66%.The stability of the detector is analyzed via an Allan variance measurement and the detector exhibits superior stability which enables a 100-s window for measurement without calibration.展开更多
By analyzing the relation between the transmission of the output mirror and the output power in an intracavity frequency doubling laser,we choose an optimal transmission of the output mirror according to the laser app...By analyzing the relation between the transmission of the output mirror and the output power in an intracavity frequency doubling laser,we choose an optimal transmission of the output mirror according to the laser application requirements.As a result,a high-power single-frequency laser at 540nm is obtained with a maximum output power of 8 W and a power stability of ±1% for three hours,whose beam quality M2 is better than 1.2.At the same time,a moderate FW power of 1.2 W is coupled out,which is enough to meet the requirements for local oscillation light and injected signal optical beams in quantum optics experiments.展开更多
We report the generation of intensity squeezing in a single-mode laser diode by weak external cavity feedback. The measurable squeezing of the output beam is 4.7%, corrected to 8.9% for the actual squeezing. This prov...We report the generation of intensity squeezing in a single-mode laser diode by weak external cavity feedback. The measurable squeezing of the output beam is 4.7%, corrected to 8.9% for the actual squeezing. This proves that intensity squeezing can be obtained by weak feedback.展开更多
We develop a frequency-tunable two-color continuous variable entangled state and demonstrate the entanglement distribution over a telecom single mode fiber.One beam of the entangled state(795 nm)can be continuously tu...We develop a frequency-tunable two-color continuous variable entangled state and demonstrate the entanglement distribution over a telecom single mode fiber.One beam of the entangled state(795 nm)can be continuously tuned over a range of 2.4 GHz and the hyperfine transitions of a rubidium D1 line are measured based on saturated absorption spectroscopy.The other beam(1560 nm)is injected into a 5-km single mode fiber to distribute the entanglement,and the entanglement evolution between the transmitted beam and its entangled counterpart is investigated.The system presented here will find potential applications in long-distance quantum information processing.展开更多
Tunable amplitude squeezing around the D_(2)line of cesium has been experimentally accomplished at room temperature in a quantum-well laser diode with light injection from a single-mode distributed Bragg-Reflector las...Tunable amplitude squeezing around the D_(2)line of cesium has been experimentally accomplished at room temperature in a quantum-well laser diode with light injection from a single-mode distributed Bragg-Reflector laser diode.While the master laser frequency is tuned,amplitude squeezing of the output light from the slave laser can be maintained at about 0.9dB throughout a tunabIe range of~l.7 GHz around the cesium D_(2)line.展开更多
The effects of the electromagnetically induced transparency and dispersion of a A-type three-level atomic system are experimentally measured with a vapour cell of Cs atoms. The steep dispersion at low absorption is ob...The effects of the electromagnetically induced transparency and dispersion of a A-type three-level atomic system are experimentally measured with a vapour cell of Cs atoms. The steep dispersion at low absorption is observed. Thus a small group velocity for the probe beam is inferred from the measured dispersion curve.展开更多
基金Supported by the National Science Foundation of China(11074156)the TYAL,the National Basic Research Program of China(2010CB923101)+1 种基金the NSFC Project for Excellent Research Team(61121064)the Shanxi Scholarship Council of China.
文摘We report a fiber-based four-state discrete modulation continuous variable quantum key distribution system based on homodyne detection.A secret key rate of 1 kbit/s is achieved at a transmission distance of 30.2 km.Two factors that result in the excess noises of the quantum key distribution system are analyzed.The first is the relative phase dithering between the signal and local fields,and the second is the local field leakage into the signal field due to the scattering process that depolarizes the local field.It is found that the latter has a significant impact on the excess noise,which is the main limiting factor to the long-distance secure quantum transmission.Some protocols are also given to decrease the excess noise effectively.
基金Supported by the National Natural Science Foundation of China under Grant No 60821004the National High-tech R&D Program of China(2011AA030203).
文摘We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser.The highest output power of 280 mW at 461.62 nm is obtained by employing a type-I phase-matched BIBO crystal and the peak-to-peak fluctuation of the power is less than±1%within three hours.The frequency stability is better than±2.22 MHz over 10 min when the laser is locked to a confocal Fabry–Perot cavity.A three-plate birefringent filter allows for the tunable range from 457 nm to 467 nm,which covers the absorption line of the strontium atoms(460.86 nm).
基金Supported by the National Natural Science Foundation of China(NSFC)(11074156)the TYAL,the National Key Basic Re-search Program of China(2010CB923101)+1 种基金the NSFC Project for Excellent Research Team(61121064)the Shanxi Scholarship Council of China.
文摘We present an ultrastable fiber-based time-domain balanced homodyne detector which can be used for precise characterization of pulsed quantum light fields.A variable optical attenuator based on bending the fiber is utilized to compensate for the different quantum efficiencies of the photodiodes precisely,and a common mode rejection ratio of above 76 dB is achieved.The detector has a gain of 3.2μV per photon and a signal-to-noise ratio above 20 dB.Optical pulses with repetition rates up to 2 MHz can be measured with a detection efficiency of 66%.The stability of the detector is analyzed via an Allan variance measurement and the detector exhibits superior stability which enables a 100-s window for measurement without calibration.
基金Supported by the National High-tech R&D Program of China(2011AA030203)the National Basic Research Program of China(2010CB923101)+1 种基金the National Nature Science Foundation of China(61008001)the Nature Science Foundation of Shanxi Province(2011021003-2).
文摘By analyzing the relation between the transmission of the output mirror and the output power in an intracavity frequency doubling laser,we choose an optimal transmission of the output mirror according to the laser application requirements.As a result,a high-power single-frequency laser at 540nm is obtained with a maximum output power of 8 W and a power stability of ±1% for three hours,whose beam quality M2 is better than 1.2.At the same time,a moderate FW power of 1.2 W is coupled out,which is enough to meet the requirements for local oscillation light and injected signal optical beams in quantum optics experiments.
基金the Youth National Natural Science Foundation of ChinaFoundation for Returned Students of Shanxi Province。
文摘We report the generation of intensity squeezing in a single-mode laser diode by weak external cavity feedback. The measurable squeezing of the output beam is 4.7%, corrected to 8.9% for the actual squeezing. This proves that intensity squeezing can be obtained by weak feedback.
基金Supported by the National Natural Science Foundation of China under Grant No 11074156the TYAL,the National Basic Research Program of China under Grant No 2010CB923101+1 种基金the NSFC Project for Excellent Research Team under Grant No 61121064the Shanxi Scholarship Council of China.
文摘We develop a frequency-tunable two-color continuous variable entangled state and demonstrate the entanglement distribution over a telecom single mode fiber.One beam of the entangled state(795 nm)can be continuously tuned over a range of 2.4 GHz and the hyperfine transitions of a rubidium D1 line are measured based on saturated absorption spectroscopy.The other beam(1560 nm)is injected into a 5-km single mode fiber to distribute the entanglement,and the entanglement evolution between the transmitted beam and its entangled counterpart is investigated.The system presented here will find potential applications in long-distance quantum information processing.
基金Supported by the National Natureal Science Foundation of China under Grant Nos.19774039 and 69837010,and the Excellent Young Teacher Foundation from National Education Department.
文摘Tunable amplitude squeezing around the D_(2)line of cesium has been experimentally accomplished at room temperature in a quantum-well laser diode with light injection from a single-mode distributed Bragg-Reflector laser diode.While the master laser frequency is tuned,amplitude squeezing of the output light from the slave laser can be maintained at about 0.9dB throughout a tunabIe range of~l.7 GHz around the cesium D_(2)line.
基金Supported by the Overseas Youth Scholar Collaboration Foundation(No.69928504)the National Natural Science Foundation of China under Grant No.69978013the Shanxi Province Young Science Foundation(No.20001016).
文摘The effects of the electromagnetically induced transparency and dispersion of a A-type three-level atomic system are experimentally measured with a vapour cell of Cs atoms. The steep dispersion at low absorption is observed. Thus a small group velocity for the probe beam is inferred from the measured dispersion curve.
