基于二阶量子干涉的光纤环路锁定研究
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摘要
基于频率纠缠光源及二阶量子干涉的时间同步协议中,利用Hong-Ou-Mandel(HOM)干涉实现纠缠光源至两臂的被同步钟环路时延平衡是实现时钟同步的关键,因而,时间同步的精度受限于HOM干涉环路两臂平衡的锁定精度。提出了一种锁定方法侧边锁定来实现干涉环路两臂平衡的锁定,并且与之前的顶端锁定方法进行了对比,分析给出了侧边锁定时的反馈速率比顶端锁定时提升了一倍,同时提高了干涉环路两臂平衡锁定的长期稳定性。利用该锁定方法,实验上实现了基于光纤路径的环路锁定。实验研究表明,随着光纤链路长度的增加,即当光纤长度分别为0,1和2km时,光纤干涉环路两臂平衡锁定的长期稳定度在2ks时均可以达到5fs,为长距离长时间高精度的量子时间同步奠定了良好的基础。
In the time synchronization protocol based on the quantum second-order interference of the entangled photon pairs,the balance of the propagation loops between the entangled bi-photons and the two clocks to be synchronized based on a Hong-Ou-Mandel(HOM)interferometer is the key point to realize the clock synchronization.The accuracy of the time synchronization is limited by the locking stability of the balance of the interference loop.In this paper,a new method of side locking is proposed to improve the locking stability of the propagation loop,and experimentally verified on fiber links with different lengths.According to the results,the feedback rate of this method is twice as fast as that of the previously-used top locking,and the long-term locking stability is obviously improved.Furthermore,by comparing the locking stability of the fiber loops with lengths of 0 km,1 km and 2 km respectively,the dependence of the locking stability on the fiber propagation length is investigated.It can be seen that though there is such dependence,the long-term stability of the fiber loop based on side locking can still reach a fairly good result:5 fs at 20 ks,which lays a good foundation for the long-term and high-precision quantum time synchronization.
In the time synchronization protocol based on the quantum second-order interference of the entangled photon pairs,the balance of the propagation loops between the entangled bi-photons and the two clocks to be synchronized based on a Hong-Ou-Mandel(HOM)interferometer is the key point to realize the clock synchronization.The accuracy of the time synchronization is limited by the locking stability of the balance of the interference loop.In this paper,a new method of side locking is proposed to improve the locking stability of the propagation loop,and experimentally verified on fiber links with different lengths.According to the results,the feedback rate of this method is twice as fast as that of the previously-used top locking,and the long-term locking stability is obviously improved.Furthermore,by comparing the locking stability of the fiber loops with lengths of 0 km,1 km and 2 km respectively,the dependence of the locking stability on the fiber propagation length is investigated.It can be seen that though there is such dependence,the long-term stability of the fiber loop based on side locking can still reach a fairly good result:5 fs at 20 ks,which lays a good foundation for the long-term and high-precision quantum time synchronization.
引文
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[2]GIOVANNETTI V,LLOYD S,MACCONE L.Quantum-enhanced positioning and clock synchronization[J].Nature,2001,412(6854):417-419.
[3]GIOVANNETTI V,LLOYD S,MACCONE L.Positioning and clock synchronization through entanglement[J].Physical Review A,2001,65(2):130-132.
[4]VALENCIA A,SCARCELLI G,SHIH Y.Distant clock synchronization using entangled photon pairs[J].Applied Physics Letters,2004,85(13):2655-2657.
[5]LAMINE B,FABRE C,TREPS N.Quantum improvement of time transfer between remote clocks[J].Physical Review Letters,2008,101(12):123601.
[6]MARI A,FARACE A,FAZIO R,et al.Measures of quantum synchronization in continuous variable systems[J].Physical Review Letters,2013,111(10):103605.
[7]LEE T E,SADEGHPOUR H R.Quantum synchronization of quantum van der Pol oscillators with trapped ions[J].Physical Review Letters,2013,111(23):234101.
[8]WALTER S,NUNNENKAMP A,BRUDER C.Quantum synchronization of a driven self-sustained oscillator[J].Physical Review Letters,2014,112(9):094102
[9]XU M H,TIERI D A,HOLLAND M J,et al.Synchronization of two ensembles of atoms[J].Physical Review Letters,2014,113(15):154101-154101.
[10]WANG J,TIAN Z,JING J,et al.Influence of relativistic effects on satellite-based clock synchronization[J].Physics Review D,2016,93(6):065008.
[11]董瑞芳,张晓斐,刘涛,等.高精度自由空间时间传递研究的新趋势[J].时间频率学报,2016,39(03):162-169.
[12]BAHDER T B,GOLDING W M.Clock synchronization based on second-order coherence of entangled photons[C]//Proceeding 7th International Conference on Quantum Communication,Glasgow:[s.n.],2004.
[13]GIOVANNETTI V,LLOYD S,MACCONE L.Quantum cryptographic ranging[J].J.Opt.B Quantum Semiclass.Opt,2002,4:S413-S414.
[14]GIOVANNETTI V,LLOYD S,MACCONE L.Clock synchronization with dispersion cancellation[J].Physical Review Letters,2001,87:117902.
[15]GIOVANNETTI V,LLOYD S,MACCONE L,et al.Conveyor-belt clock synchronization[J].Physical Review Letters A,2004,70:043808.
[16]HONG C K,OU Z Y,MANDEL L.Measurement of subpicosecond time intervals between two photons by interference[J].Physical Review Letters,1987,59:2044-2047.
[17]王盟盟,权润爱,董瑞芳,等.长光纤HOM干涉平衡的稳定控制[C]//全国量子光学学术报告会,延吉:中国物理学会,2014.
[18]QUAN Run-ai,WANG M,DONG Rui-fang,et la.Characterization of frequency entanglement under extended phase-matching conditions[J].Applied Physics B,2015,118(3):431-437.
[19]QUAN Run-ai,ZHAI Yi-wei,DONG Rui-fang,et al.Demonstration of quantum synchronization based on second-order quantum coherence of entangled photons[J].Scientific Reports,2016,6:30453.