Quantum key distribution system to overcome intercept-resend and detector-control quantum hacking

A system comprising:

• a transceiver comprising:
• a light source configured to generate a faint pulse;
• a state converter including an interferometer, wherein the state converter is configured to convert the faint pulse from a polarization-path state to a time-polarization state with a leading time bin and a lagging time bin, wherein the state converter includes a polarization converter in an arm of the interferometer to rotate light within the arm to an orthogonal polarization;
• and
• a polarization randomizer to receive the faint pulse from the state converter, wherein the polarization randomizer applies a random polarization transformation to the faint pulse prior to transmission of the faint pulse through a communication channel;
• and
• a quantum bit encoder to receive the faint pulse from the transceiver over the communication channel, wherein the quantum bit encoder comprises:
• a phase modulator configured to apply a differential phase shift between the leading time bin and the lagging time bin of the faint pulse received through the communication channel as an encoded bit;
• and
• a Faraday mirror to reflect the faint pulse back to the transceiver and rotate a polarization of the faint pulse to an orthogonal state;
• wherein the transceiver is further configured to receive a return pulse through the communication channel, wherein the polarization randomizer is configured to apply an inverse of the random polarization transformation to the return pulse;
• wherein the transceiver further comprises three or more detectors configured to measure the return pulse at time-gated timeslots associated with possible paths of the return pulse through at least the polarization randomizer and the state converter;
• wherein reception of the faint pulse from the quantum bit encoder as the return pulse triggers a detector in a first detector subset of the three or more detectors;
• and
• wherein reception of a faked-state pulse from a third party as the return pulse results in a non-zero probability of triggering of a detector in a second detector subset of the three or more detectors.

A system comprising:

• a quantum key distribution (QKD) system comprising:
• a transceiver comprising:
• a light source configured to generate a faint pulse;
• a state randomizer configured to impart a random state transformation to one or more qubits associated with the faint pulse prior to transmission of the faint pulse through a communication channel;
• a quantum bit encoder comprising:
• a modulator configured to encode an encoded bit on the faint pulse received through the communication channel;
• and
• a mirror to reflect the faint pulse back to the transceiver;
• wherein the transceiver is further configured to receive a return pulse through the communication channel, wherein the state randomizer is configured to apply an inverse of the random state transformation to the return pulse;
• wherein the transceiver further comprises three or more detectors configured to measure the return pulse at time-gated timeslots associated with possible paths of the return pulse through the transceiver;
• wherein reception of the faint pulse from the quantum bit encoder as the return pulse triggers a detector in a first detector subset of the three or more detectors;
• and
• wherein reception of a faked-state pulse from a third party as the return pulse results in a non-zero probability of triggering of a detector in a second detector subset of the three or more detectors
• wherein the transceiver determines the encoded bit based on which detector in the first detector subset is triggered;
• and
• wherein the faint pulse is one of a series of faint pulses, wherein encoded bit is one of a series of encoded bits associated with the series of faint pulses, wherein at least one of the transceiver or the quantum bit encoder generate an encryption key based on the series of encoded bits;
• a first client to encrypt data based on the encryption key and transmit the encrypted data across an additional communication channel;
• and
• a second client to decrypt data received over the communication channel based on the encryption key.