Precision photon synchronization

A method for synchronizing a first entanglement source

• at a first ground station with a second entanglement source
• at a second ground station via a satellite, the method comprising:
• synchronizing the first entanglement source with the second entanglement source;
• transmitting a first qubit from the first entanglement source to the satellite;
• transmitting a second qubit from the second entanglement source to the satellite;
• and
• performing an optical Bell state measurement on the first qubit and the second qubit at the satellite to entangle qubits at the first entanglement source with qubits at the second entanglement source.

A system for precision synchronization of photons, comprising:

• a first ground station comprising:
• a frequency synthesizer to create a repetition rate;
• a laser to receive the repetition rate and generate pulses;
• and
• an entanglement source to receive pulses and generate entangled photons;
• wherein the first ground station generates a first synchronization signal based on the pulses generated by the laser;
• and
• a second ground station comprising:
• a laser to generate pulses;
• and
• an entanglement source to receive the pulses and generate entangled photons;
• wherein the second ground station generates a second synchronization signal based on the pulses generated by the laser and transmits the second synchronization signal to the first ground station;
• wherein the first ground station further comprises:
• a timing measurement apparatus to measure a phase difference between the first synchronization signal and the second synchronization signal;
• an optical Bell state measurement apparatus to receive one entangled photon from the first ground station and the second ground station and determine an optical Bell state;
• and
• a control loop in communication with the timing measurement apparatus and the frequency synthesizer to vary the repetition rate.