Method for performing quantum secure direct communication in quantum communication system, and apparatus therefor

A transmitting end performing quantum secure direct communication (QSDC) for transmitting a message based on differential time coding, in a quantum communication system, comprising:

• a transmitter for transmitting a radio signal;
• a receiver for receiving the radio signal;
• at least one processor;
• and
• at least one computer memory operably connectable to the at least one processor, and storing instructions of performing operations when executed by the at least one processor,
• wherein the operations include
• receiving, from a receiving end on a quantum channel, (i) at least one initial time state configured by including a time interval equal to a dead time of a single photon detector of the receiving end;
• receiving, from the receiving end on a classical channel, time state location information for selecting a specific initial time state for encoding of information transmitted to the receiving end;
• selecting the specific initial time state for the encoding, based on the time state location information;
• generating an encoding time state by encoding the information, based on the selected specific initial time state;
• generating the encoding time state by applying a time shift based on a value of the information being encoded;
• and
• transmitting a message including the encoding time state to the receiving end through the quantum channel, and
• wherein the message is restored based on a differential time between information on the at least one initial time state information stored in the receiving end and information on the encoding time state.

A quantum secure direct communication (QSDC) method by which a receiving end receives a message based on differential time coding, in a quantum communication system, comprising:

• transmitting, to a transmitting end on a quantum channel, (i) at least one initial time state configured by including a time interval equal to a dead time of a single photon detector of the receiving end;
• transmitting, to the transmitting end on a classical channel, time state location information for selecting a specific initial time state for encoding of information transmitted to the transmitting end,
• wherein the specific initial time state for the encoding in the transmitting end is selected based on the time state location information;
• receiving, from the transmitting end, a message including an encoding time state generated by applying a time shift based on a value of the information encoded based on the specific initial time state;
• and
• restoring the information based on the at least one initial time state information and the encoding time state information stored in the receiving end.