Quantum Key Distribution

• Polarisation can be one of two states -> represent a qubit

Protocol

1. Alice chooses a string of random bits and a random choice of basis for each bit(private)
2. Alice encodes each bit onto a string of qubits using basis she chose
3. Bob measures each qubit at random(private)
4. Bob and Alice publicly share which basis used for each qubit
5. Finally, Bob and Alice share random sample of their keys
   if samples match, they can be sure that their transmission is successful