We propose a scheme for realizing an unconventional three-qubit controlled-phase gate via the Rydberg blockade mechanism.The qubit is encoded by atomic ensembles that are trapped in optical traps and fixed on an atom ...We propose a scheme for realizing an unconventional three-qubit controlled-phase gate via the Rydberg blockade mechanism.The qubit is encoded by atomic ensembles that are trapped in optical traps and fixed on an atom chip.Because of the collective nature of the encoding and the Rydberg blockade mechanism,the scheme do not require separate addressing of individual atoms.The time needed for the gate operation is much shorter than that in a similar scheme.In addition,we show the gate can be used as a basic tool for effective generation of large-scale 2D cluster states.展开更多
Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In or...Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In order to improve the phase-coding modulation rate, we proposed a new digital-modulation method in this paper and constructed a compact and robust prototype of QKD system using currently available components in our lab to demonstrate the effectiveness of the method. The system was deployed in laboratory environment over a 50 km fiber and continuously operated during 87 h without manual interaction. The quantum bit error rate （QBER） of the system was stable with an average value of 3.22% and the secure key generation rate is 8.91 kbps. Although the modulation rate of the photon in the derno system was only 200 MHz, which was limited by the Faraday- Michelson interferometer （FMI） structure, the proposed method and the field programmable gate array （FPGA） based electronics scheme have a great potential for high speed QKD systems with Giga-bits/second modulation rate.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.61275215 and 11004033)the Natural Science Foundation of Fujian Province (Grant No.2010J01002)the National Fundamental Research Program of China (Grant No.2011CBA00203)
文摘We propose a scheme for realizing an unconventional three-qubit controlled-phase gate via the Rydberg blockade mechanism.The qubit is encoded by atomic ensembles that are trapped in optical traps and fixed on an atom chip.Because of the collective nature of the encoding and the Rydberg blockade mechanism,the scheme do not require separate addressing of individual atoms.The time needed for the gate operation is much shorter than that in a similar scheme.In addition,we show the gate can be used as a basic tool for effective generation of large-scale 2D cluster states.
基金supported by the National Key Basic Research Program of China(Grant Nos.2011CBA00200 and 2011CB921200)the National Natural Science Foundation of China(Grant Nos.61201239,6120511811304397 and 61475148)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB01030100 and XDB01030300)
文摘Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In order to improve the phase-coding modulation rate, we proposed a new digital-modulation method in this paper and constructed a compact and robust prototype of QKD system using currently available components in our lab to demonstrate the effectiveness of the method. The system was deployed in laboratory environment over a 50 km fiber and continuously operated during 87 h without manual interaction. The quantum bit error rate （QBER） of the system was stable with an average value of 3.22% and the secure key generation rate is 8.91 kbps. Although the modulation rate of the photon in the derno system was only 200 MHz, which was limited by the Faraday- Michelson interferometer （FMI） structure, the proposed method and the field programmable gate array （FPGA） based electronics scheme have a great potential for high speed QKD systems with Giga-bits/second modulation rate.
