A method for a quantum key distribution from a first target node to a second target node across a network via an entanglement-based protocol, including the following steps: transferring entangled particles from a load node to the first target node and to at least one intermediate node; generating a quantum key with the entangled particles transferred to the first target node and the at least one intermediate node; transmitting the quantum key to the second target node on a first path located on the network with a stage of secure quantum key transmission agreement starting from the at least one intermediate node by encrypting intervals of binary nodes with pre-shared quantum keys; and providing a secure communication with the quantum keys between the first target node and the second target node on a second path located on the network.

An imaging and quantum cryptography apparatus comprising a light-refracting optical setup (10 a light-directing optical setup (102), an imaging sensor (103) capturing light refracted the light-refracting optical setup and directed to the imaging sensor by the light-directing optical setup and at least one of a quantum distribution (QKD) transmitter (104) generating a QKD light signal and transmitting QKD light signal via the light-directing optical setup and through the light-refracting optical setup and a QKD receiver (105) acquiring and decoding light signals refracted from the light-refracting optical setup and directed to the QKD receiver by the light-directing optical setup. The imaging sensor, the at least one of QKD transmitter and QKD receiver, and the alignment unit, all use the same light-directing optical setup and the same light-refracting optical setup.

A key management device according to an embodiment includes one or more hardware processors configured to function as a determination unit, a generation unit, and a supply unit. The determination unit determines a type of request data requested by a request message transmitted from an application that performs encrypted data communication. The generation unit generates a response message including at least one of a random number and an encryption key shared by quantum key distribution (QKD) via a communication network according to a type of the request data. The supply unit supplies the response message to the application.

Disclosed is a quantum key distribution system using an RFI (reference frame independent) QKD (quantum key distribution) protocol, which includes a first signal processing circuit that generates transmission basis information and transmission bit information, a quantum channel transmitter that generates a single photon or coherent light, and modulates the single photon or the coherent light based on the transmission basis information and the transmission bit information to generate a quantum signal, a quantum channel receiver that receives the quantum signal through a quantum channel and detects reception bit information from the quantum signal based on reception basis information, and a second signal processing circuit that generates the reception basis information, transmits the reception basis information to the first signal processing circuit through a public channel, and receives the transmission basis information from the first signal processing circuit through the public channel.

The present disclosure relates to a quantum key distribution (QKD) method based on a tree QKD network. In a tree network, when parent nodes of a source node and a destination node are the same node, if the parent nodes are untrusted nodes, the source node and the destination node take the parent nodes as an MDI-QKD detector to generate a key, and if the parent nodes are trusted nodes, a shared key is directly transferred through XOR relay; and when the parent nodes of the source node and the destination node are not the same node and there are discontinuous untrusted relay nodes in a transmission path, the untrusted nodes are taken as an MDI-QKD detector to generate a key, and then the shared key is transferred through XOR relay.

Described is a method of setting up a plurality of quantum communications links, forming a quantum network providing provably secure communications and internet services over intercontinental distances without requiring direct line of sight communication or the intermediate use of the entanglement resource of satellites. Also described is a quantum communicator device for use in this method. Two or more quantum memory units are disposed at a first location, an entangled link is set up between at least two of the quantum memory units, at least one of the quantum memory units sharing in the entangled link is physically transported to a second location. The quantum communicator device comprises communications nodes, an optical interface to set up entanglement to other devices and storage nodes, each node in the form of a quantum memory unit capable of storing quantum information for a desired length of time, i.e. weeks or longer.

A quantum key distribution (QKD) node apparatus and a QKD method therein. The QKD node apparatus may include a QKD module for generating quantum keys and quantum key IDs, a quantum key synchronization management module for storing the quantum keys and the quantum key IDs as outbound and inbound quantum keys in a distributed manner and sharing the outbound and inbound quantum keys with a second QKD node apparatus, and a quantum key orchestration module for delivering a master key and a master key ID to a secure application connected therewith in response to a request for the master key with the ID of a second secure application and delivering a packet including the master key encrypted with the outbound quantum key shared with the second QKD node apparatus, the master key ID, and a quantum key ID, to the second QKD node apparatus.

A method of data transmission, and more particularly a secure method of data transmission. The method comprises generating and sending a classical data stream and quantum data stream from a source to a destination. The step of generating and sending a classical data stream from the source to the destination comprises encrypting the data stream with the repeated use of a once-seen pad. Observing the quantum data stream received at the destination, may indicate eavesdropping and if so, the classical data stream is modified and sent from the source to the destination, including stopping the repeated use of the once-seen pad. The same once-seen pad may be used a number of times provided no third party has seen data encrypted by the once-seen pad.

Devices, systems, and methods for ambient-temperature quantum information buffering, storage, and communication are provided enabling receiving a quantum communication (for example, photons holding quantum information, e.g., qubits), storing the qubits in a room-temperature scalable quantum memory device, selectively retrieving the qubits, performing filtering, and extracting the quantum communication with a controllable delay.

Quantum network devices, systems, and methods are provided to enable long-distance transmission of quantum bits (qubits) for applications such as Quantum Key Distribution (QKD), entanglement distribution, and other quantum communication applications. Such systems and methods provide for separately storing first, second, third, and fourth photons, wherein the first and second photons and the third and fourth photons are respective first and second entangled photon pairs, triggering a synchronized retrieval of the stored first, second, third, and fourth photons such that the first photon is propagated to a first node, the second and third photons are propagated to a second node, and the fourth photon is propagated to a third node, and creating a new entangled pair comprising the first and fourth photons at the first and third nodes to transmit quantum information.