System and method for quantum key distribution

A method for quantum key distribution (QKD) between a first location (A) and a second location (B) through an intermediate location (T), the method comprising:

• executing a quantum phase between the first location (A) and the intermediate location (T) to determine a first location raw data string (RA) at the first location and a first-intermediate raw data string (RAT) at the intermediate location (T);
• executing a quantum phase between the second location (B) and the intermediate location (T) to determine a second location raw data string (RB) at the second location (B) and a second-intermediate raw data string (RTB) at the intermediate location (T);
• calculating, at the intermediate location (T), announcement data based on a function (F) of the first-intermediate raw data string (RAT) and the second-intermediate raw data string (RTB);
• announcing, at the intermediary location (T), the announcement data over a classical channel;
• and
• deriving, at each of the first and second locations (A, B), a secret key (KAB) based on the first location raw data string (RA), the second location raw data string (RB), and the announcement data and on communications between the first and second locations (A, B) via the classical channel.