Coherent State Quantum Key Distribution with Multi Letter Phase-Shift Keying

Understand

We present a protocol for quantum key distribution using discrete modulation of coherent states of light.

• Information is encoded in the variable phase of coherent states which can be chosen from a regular discrete set ranging from binary to continuous modulation, similar to phase-shift-keying in classical communication.
• Information is decoded by simultaneous homodyne measurement of both quadratures and requires no active choice of basis.
• The protocol utilizes either direct or reverse reconciliation, both with and without postselection.