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Global Time Distribution via Satellite based Sources of Entangled Photons�QuILT - 2022

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Quantum Clock Synchronization

Satellite based QCS network

A satellite based QCS network – Motivation

Why QCS over classical sync techniques?

Tight time correlations (≈ 1 fs)

High precision (< 1 ns) with very low acquisition times (< few milliseconds)
A priori knowledge travel time not needed – secure against symmetric delay attacks

Polarization correlations - Entanglement

Why a space-based network?

Low loss due to transmission in vacuum compared to fiber optic cables
Large coverage area (intercontinental synchronization with modest # of satellites)
Much more difficult to attack

A satellite based QCS network – Applications

Synchronizing two clocks in relative motion

SNR of correlation functions

For fixed t_AB SNR increases monotonically with increasing t_acq.
Not true in this case – new peak starts to appear after every t_shift amount of time.

Parameters for simulating the satellite-ground quantum communication channels

Precision is determined by acquisition time and link loss

A game of shadows

Visibility condition –

boundary of precision shadow

Precision shadows –

effect of transmissivity and relative motion

A near-term QCS network – continental US

Effect of increasing holdover time – visibility shadow and precision shadow

Sync for city pairs – effect of hold over time

Constellation choice, relativistic effects, fundamental science, quantum security and much more…..

Choosing a minimalistic satellite constellation which provides global coverage at precision > GPS
GPS: 1^st order SR + GR effects = 38000 nano-sec/day = 0.5 pico-sec/milli-sec
Approximate trajectory knowledge, weaker sources, more loss
More precision – higher order relativistic effects – fundamental science
Effect on security (delay attacks, asymmetric attacks, counterfeiting)??

Thank you for your attention - short quiz