Quantum communication network

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 method for operating 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;
• and
• at least three ports adapted to communicate with at least one other node;
• and
• an optical switch,
• wherein said method comprises operating said optical switch 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 method of securely transmitting a key from a source node to a destination node, wherein the source node and the destination node being separated by a sequence of N nodes, where N is an integer of at least 2,

• the method comprising:
• dividing the quantum key of length KN into N parts;
• sending each part of the key via a subset of the sequence of N nodes wherein each subset consists of N−1 of the nodes, such that each part of the key bypasses at least one of the N nodes;
• and
• combining the N parts of the key transmitted via the subsets of nodes to produce the key with a length K.