High-precision nonlocal temporal correlation identification of entangled photon pairs for quantum clock synchronization

Abstract

The ability to identify the correlation in the remotely departed entangled photon pairs is critical to measure the time difference for subsequent synchronization between independent time scales. The first remote correlation detection was reported in 2009, which extracts the time difference via the algorithm of iterative fast Fourier transformations (FFTs) and their inverse.Based on this algorithm, the resolution is restricted due to the pre-processing program of the time sequences. In this paper an improved algorithm is proposed both in the resolution and time difference precision, which realizes well-performed coincidence identification with a flexible resolution down to 1 ps. With a common time scale reference, the measured time offset between two timing signals detected nonlocally has achieved a standard deviation of 0.72 ps. This implementation provides a solid basis for the applications of entanglement-based quantum technologies in the systems of high-precision clock synchronization, ranging system and quantum communications.

Implementation of quantum synchronization over a 20-km fiber distance based on frequency-correlated photon pairs and HOM interference

“…In the time offset measurement part, the output of D3 and D4 were delivered to two even timers (ET, A033-ET, Eventech Ltd.) for arrival time tagging and recording, which were both referenced to a H-maser. Through the second-order correlation calculation of the ET results 15 , the absolute time offset could be obtained. For comparison, a time-correlated single-photon counting system (TCSPC, Pi-coHarp 300, PicoQuant Inc.) was also used for proof-ofprinciple QCS, where the clicks of the two detectors are regarded as the virtual clocks.…”

Nonlocal subpicosecond delay metrology using spectral quantum interference

“…Inserting Eqs. (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) into Eq. ( 26), and assuming the biphoton joint spectral amplitude (JSA), consisting of phase matching function Φ(Ω) and the complex amplitude functions H (S) and H (I) , to be slowly varying with respect to the narrow width δΩ of the frequency filter f , allows us to effectively consider the JSA at the center frequencies of the signal-idler filters ω 0 ± Ω 0 .…”

“…There have been previous investigations on measuring temporal correlations of entangled photons via coincidence measurement, purposed for high-precision synchronization between remote sites [12,13,22]. Entanglement offers a distinguishing non-local resource [23][24][25][26] that can be exploited in the quantum network architecture.…”

“…A simple time-resolved correlation measurement using commercially available superconducting nanowire SPDs is however limited by timing jitters on the order of 50 ps. There have been demonstrations to push the limits of temporal sensitivity both by improving the SPD hardware [27] and by modifying the event timing algorithms [22]. However, nonlocal biphoton delay measurement with a sensitivity independent of detector/event timer resolution has so far not been reported.…”

Clock synchronization with correlated photons

“…Quantum clock synchronization protocols have been proposed to tackle synchronizing distant clocks [31][32][33] in multi-partite network settings [34,35] and with quantum-enhancement beyond the possibilities of classical physics [36]. To this end, investigations over the last years have focused on exploitation of the temporal correlations of time-energy entangled photons created via parametric down conversion [37][38][39][40]. When photon pairs originate from common creation event, this gives rise to a narrow correlation peak in their arrival time at remote receivers.…”