A path computation engine, PCE, (100) for an optical communications network comprising a plurality of nodes and a plurality of links. The PCE comprises a processor and memory comprising instructions executable by the processor whereby the PCE is operative to: receive a request to configure a quantum key, Qkey, path from a first node to a second node in the optical communications network for a quantum key distribution, QKD, signal for a quantum key for a secure data transmission signal; calculate a feasible Qkey path from the first node to the second node that is logically different to a traffic path from the first node to the second node for the secure data transmission signal, wherein the Qkey path is feasible if an optical signal power originating from the secure data transmission signal within the Qkey path, caused by optical interference of the secure data transmission signal with the QKD signal, is below a predetermined threshold value; and generate a control signal comprising instructions arranged to configure said feasible Qkey path.

A node for a quantum communication network, said node comprising: a quantum transmitter, said quantum transmitter being adapted to encode information on weak light pulses; a quantum receiver, said quantum receiver being adapted to decode information from weak light pulses; at least three ports adapted to communicate with at least one other node; and an optical switch, said optical switch being configured to selectively connect the quantum transmitter and receiver to the ports such that the switch controls which of the ports is in communication with the quantum transmitter and quantum receiver.

A quantum communications system includes a first quantum repeater and a second quantum repeater each positioned at a repeater node and each having a first quantum memory and a second quantum memory. A first channel switch is optically coupled to the first quantum repeater and a second channel switch is optically coupled to the second quantum repeater. Further, a first sub-channel extends between and optically couples the first channel switch and the first quantum memory of the first quantum repeater, a second sub-channel extends between and optically couples the first channel switch and the first quantum memory of the second quantum repeater, a third sub-channel extends between and optically couples the second channel switch and the second quantum memory of the first quantum repeater, and a fourth sub -channel extends between and optically couples the second channel switch and the second quantum memory of the second quantum repeater.

The present disclosure relates to a quantum key distribution (QKD) method based on a tree QKD network. The method includes: judging a position of a parent node of the source node S.sub.0 and a position of a parent node of the destination node S.sub.d; if the parent node is a trusted relay node, directly transferring an initial shared key of the source node S.sub.0 and the parent node to the destination node S.sub.d according to an exclusive OR (XOR) relay scheme, and ending the process; and if the parent node is an untrusted relay node, emitting, by the source node S.sub.0 and the destination node S.sub.d, photons to a measuring-device-independent quantum key distribution (MDI-QKD) receiver of the parent node through a QKD emitter, generating a shared key by an MDI-QKD method, then transmitting the shared key according to the XOR relay scheme, and ending the process.

A trusted node, for quantum key distribution, has a quantum key engine, a quantum key controller and a trusted node controller. The quantum key engine exchanges quantum keys. The quantum key controller directs encryption and decryption. The trusted node controller directs the quantum key controller and the quantum key engine, and has no direct access to keys and data protected by the system, including unencrypted quantum keys.

A system and method are described for proactively performing key swaps among nodes in a quantum key distribution (QKD) network. The method includes determining a routing solution for nodes in the QKD network; making the routing solution available to the nodes in the QKD network; and initiating key swaps among the nodes in the QKD network according to the routing solution, prior to key requests being made within the QKD network. The method can also include continuously performing key swaps among the nodes in the QKD network according to the routing solution; detecting a change in capacity and/or a change in demand on one or more links within the QKD network; determining a new routing solution based on the detected change; and continuously preforming subsequent key swaps according to the new routing solution.

Aspects of the subject disclosure may include, for example, determining that quantum entanglement be established between first and second nodes of a service provider network including a software defined network (SDN) that facilitates delivery of a service to a subscriber and identifying a path between the first node and the second node based on pre-provisioned information supplied by the SDN. A path length of the path is estimated based on the pre-provisioned information supplied by the SDN, and a repeater node is selected responsive to the path length exceeding a threshold, wherein the path includes a first segment having a segment length that does not exceed the threshold. A quantum entanglement state is shared between the first and second nodes based on transportation of a first photon of a first entangled pair of photons via the first segment. Other embodiments are disclosed.

A system and method for determining a secret cryptographic key shared between a sending unit and a receiving unit by using a communication channel comprising spatially separated amplifiers for secure long-distance communication includes transmitting a sequence of electromagnetic pulses via the communication channel through the amplifiers for establishing a shared secret cryptographic key, wherein each electromagnetic pulse corresponds to a bit of a random bit sequence according to a ciphering protocol, and at least one ciphering parameter is determined by maximizing the expected key generation rate using an information theory model, wherein a measured signal loss and at least one amplification parameter are taken into account as input parameters to the information theory model.

A quantum key distribution (QKD) system comprising: an emitter (110) adapted to generate a QKD free-space signal, a transmitter station (220) adapted to receive the free-space signal from the emitter (110), and a remote QKD receiving station (250) supporting a QKD receiver (160) located at a different location than the transmitter station, wherein the transmitter station is adapted to receive said free space signal from the emitter and to forward said signal through a fiber link (400) to the QKD receiver (160) in said remote QKD receiving station (250).

A quantum communication system has a plurality of trusted nodes. Each trusted node has a quantum key controller, and a quantum transmitter or a quantum receiver. The trusted nodes are configurable as first and second endpoint trusted nodes and middle-trusted nodes between endpoint trusted nodes. The first endpoint trusted node encrypt data comprising a first key, using a first quantum key. Each middle-trusted node decrypts, using a preceding quantum key, and re-encrypts using a succeeding quantum key. The second endpoint trusted node decrypts using a quantum key, so that the first and second endpoint trusted nodes each have the first key.