Quantum-secured clock synchronisation using polarisation-entangled photons - Ben Sparkes

Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) provide accurate time and positioning information, which is essential for the operation of navigation systems, communication networks and electricity grids. However, the radio signals transmitted from GPS satellites to receivers can be spoofed, resulting in false time and position information being sent to the GPS receiver.
Protocols using the time-correlation properties of entangled photon pairs have been proposed as a means of providing verified time synchronisation with sub-nanosecond precision. Here we will present an experimental demonstration of quantum-secured clock synchronisation using polarisation-entangled photon pairs transmitted over a free-space link over a three-day period. We also investigate the effect of interference – including signal blockage, distance alteration, polarisation rotation and added noise - on the clock synchronisation protocol.