The present disclosure in some embodiments provides a method and an apparatus for providing a quantum cryptographic key distribution stabilization, which can quickly and efficiently compensate for an error caused by a temperature change, a change in polarization of a transmission path of an optical system included in a quantum cryptographic key distribution system in a cost-effective manner working perfectly with the very conventional quantum cryptographic key distribution system.

According to an embodiment, a communication device is connected to another communication device through a quantum communication channel and a classical communication channel to share an encryption key. The device includes a photon detector, a measurer, a difference generator, and a transmitter. The photon detector is configured to detect photons transmitted from the other communication device through the quantum communication channel. The measurer is configured to measure time when each photon is detected by the photon detector as time stamp information. The difference generator is configured to generate difference time stamp information as a difference between time obtained by adding particular information to the time indicated by the time stamp information previously measured by the measurer and time indicated by the time stamp information subsequently measured by the measurer. The transmitter is configured to transmit the difference time stamp information to the other communication device through the classical communication channel.

Disclosed herein are technologies regarding a communication device and server which are capable of cryptographic communication based on quantum cryptography. The communication device includes: a quantum signal generation unit configured to generate a series of first quantum signals by using a first quantum filter; an optical transmission unit configured to send the series of first quantum signals to a server; and a processor configured to select the first quantum filter based on a series of randomly generated first quantum states, and to control the quantum signal generation unit to generate the series of first quantum signals by using the first quantum filter.

A method and a system for encryption and decryption based on continuous-variable quantum neural network CVQNN. The method includes: updating a weight of the CVQNN with a training sample; triggering, by a sender, a legal measurement bases synchronization between the sender and the CVQNN; converting, by the sender, the information to be sent into a quadratic plaintext according to the synchronized measurement bases, and sending the quadratic plaintext to the CVQNN; encrypting, by the CVQNN, a received quadratic plaintext, and sending an encrypted quadratic plaintext to a receiver; after receiving the encrypted quadratic plaintext, sending by the receiver the encrypted quadratic plaintext to the CVQNN for decryption to obtain decrypted information. The embodiments implement data encryption and decryption by introducing CVQNN model and synchronization measurement technology. The embodiments provide advantages of high reliability, high security and easy realization.

According to an embodiment, a receiver is connected to transmitters through photon communication channels and data communication channels to generate identical cryptographic keys to be shared with each transmitter. The receiver includes a sharing unit, a key distilling unit, a data communication controller, and a calculator. The key sharing unit is configured to generate a shared bit string through quantum key distribution with each transmitter via a corresponding photon communication channel. The key distilling unit is configured to generate the cryptographic keys from the respective shared bit strings. The data communication controller is configured to receive from each transmitter first information about a corresponding cryptographic key via a corresponding data communication channel. The calculator is configured to calculate the photon timeslots based on at least the first information. The data communication controller is configured to transmit the photon timeslots to the transmitters.

According to an embodiment, a quantum key distribution device includes a quantum key distributor, a sifter, a corrector, an identifier, a classifier, a calculator, and a privacy amplifier. The quantum key distributor obtains a photon string from a photon string of two or more intensities of light pulses. The sifter obtains pulse information indicating the light pulse to which each bit of a shared bit string corresponds. The corrector corrects an error included in the shared bit string and generates a post-correction bit string. The identifier generates error position information. The classifier classifies each bit of the post-correction bit string. The calculator calculates the error rate for each light pulse and each base using the error position information. The privacy amplifier generates a cryptographic key from the post-correction bit string on the basis of the error rate.

A communication device in embodiments is a quantum key distribution device connectable to another quantum key distribution device through a quantum communication channel to share an encryption key therebetween, and includes a common processing unit, one or more individual processing units, and a distribution unit. The common processing unit outputs intermediate data based on bit information obtained by transmitting or receiving sequence of photons with the another quantum key distribution device through the quantum communication channel. Each individual processing unit generates or provides the encryption key in accordance with the intermediate data. The distribution unit distributes the intermediate data that is output from the common processing unit to two or more distribution destination that include the individual processing units.

According to an embodiment, a communication device is connected with another communication device through a quantum communication channel with a shared encryption key. The device includes a communication unit, a sifter, a corrector, a calculator, and an extractor. The communication unit is configured to acquire a sequence of photons through the quantum communication channel and acquire a photon bit string corresponding to the sequence of photons. The sifter is configured to generate a shared bit string from the photon bit string by sifting processing using basis information. The corrector is configured to generate a corrected bit string by correcting an error included in the shared bit string. The calculator is configured to generate a hash-calculated bit string by performing hash calculation on the corrected bit string. The extractor is configured to extract, as the key, from the hash-calculated bit string, a bit string having the length of the key.

Provided are a quantum key distribution method, device, and system. The quantum key distribution system may include a transmitter configured to split an optical signal into a first optical signal passing through a first path (P1) and a second optical signal passing through a second path (P2), which is longer than the first path (P1), and to sequentially transmit the first optical signal and the second optical signal; and a receiver configured to receive the first optical signal and the second optical signal incident through a quantum channel and transmit the first optical signal and the second optical signal back to the transmitter through the quantum channel after passing through a polarization-dependent element, being reflected by a Faraday mirror, and passing through the polarization-dependent element again.

The present invention, which is used for continuous variable quantum key distribution (CVQKD) with asynchronous local oscillators, relates to a system for performing a phase compensation of a scheme of using LO phase estimation and feedback at a receiver (Bob) using a pilot signal from a transmitter (Alice) and a scheme of measuring quantum state data using an LO having a predetermined phase at the receiver (Bob) and estimating and feeding back an LO phase through multi-dimensional reconciliation (MDR).