Apparatus and method for multi-user quantum key distribution

An apparatus for multi-user quantum key distribution, comprising:

• at least one processor;
• a memory having instructions stored thereon, which, when executed by the at least one processor, cause the at least on processor to function as:
• a quantum random number generation unit configured to generate a key bit string of a shared key to be distributed to each of a plurality of quantum key client devices, based on quantum states;
• a qubit generation unit configured to generate key qubit pairs based on the key bit string of the shared key, to generate verification qubit pairs by selecting one or more of quantum states having non-orthogonality therebetween, and to generate transmission qubit pairs based on the key qubit pairs and the verification qubit pairs;
• a qubit transmission unit configured to transmit the transmission qubit pairs to each of the quantum key client devices through a quantum channel;
• and
• a classical signal transmission/reception unit configured to disclose information related to the transmission qubit pairs through a classical channel.

A quantum key client device comprising:

• at least one processor;
• a memory having instructions stored thereon, which, when executed by the at least one processor, cause the at least on processor to function as:
• a qubit measurement unit configured to measure transmission qubit pairs, received from a multi-user quantum key distribution apparatus through a quantum channel, based on a measurement basis;
• a quantum random number generation unit configured to select a sequence of the measurement bases based on quantum states;
• a classical signal transmission/reception unit configured to receive pieces of information related to the transmission qubit pairs through a classical channel;
• and
• a measurement result processing unit configured to determine, based on a comparison, whether the pieces of information related to the transmission qubit pairs are identical to qubit measurement values obtained by measuring the transmission qubit pairs, to verify security of the quantum channel, and to decode the qubit measurement values into a key bit string of a shared key to be distributed by the multi-user quantum key distribution apparatus.