Abstract: The invention relates to a IM bias voltage determining method adapted to determine an IM bias voltage corresponding to a desired Quantum Bit Error Rate based on the following formula Q ? ( V IM ) = Q 0 + R err R err + R cor where Q(VIM) is the QBER dependent of the IM bias voltage VIM, Q0 is the optimal minimal QBER, Rerr is the number of erroneous detections, Rcor is the number of correct detections and VIM is the IM bias voltage.

Abstract: A tamper detecting component for a quantum communication system is a trusted node, configurable as a first endpoint trusted node, a middle-trusted node and a second endpoint trusted node. The trusted node has a tamper detection module and a secure memory. The tamper detection module deletes critical system parameters responsive to detecting physical tampering. The trusted node, as the first endpoint trusted node, exchanges a quantum key, encrypts data and transmits encrypted data. The trusted node as the middle-trusted node exchanges a quantum key, exchanges another quantum key, decrypts and re-encrypts data and transmits encrypted data. The trusted node as the second endpoint trusted node exchanges a quantum key, and decrypts data.

Abstract: 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.

Abstract: 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.

Abstract: The invention relates to a IM bias voltage determining method adapted to determine an IM bias voltage corresponding to a desired Quantum Bit Error Rate based on the following formula Q ? ( V IM ) = Q 0 + R err R err + R cor where Q(VIM) is the QBER dependent of the IM bias voltage VIM, Q0 is the optimal minimal QBER, Rerr is the number of erroneous detections, Rcor is the number of correct detections and VIM is the IM bias voltage.

Abstract: 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.

Abstract: 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.

Abstract: A tamper detecting component for a quantum communication system is a trusted node, configurable as a first endpoint trusted node, a middle-trusted node and a second endpoint trusted node. The trusted node has a tamper detection module and a secure memory. The tamper detection module deletes critical system parameters responsive to detecting physical tampering. The trusted node, as the first endpoint trusted node, exchanges a quantum key, encrypts data and transmits encrypted data. The trusted node as the middle-trusted node exchanges a quantum key, exchanges another quantum key, decrypts and re-encrypts data and transmits encrypted data. The trusted node as the second endpoint trusted node exchanges a quantum key, and decrypts data.

Abstract: For distributing a sequence of symbols, an emitter station transmits to a receiver station quantum systems through a quantum channel. Each of the quantum systems belongs to a set of at least two non-orthogonal quantum states and comprises a group of at least two weak coherent states of an electromagnetic field. Each weak coherent state is in a time bin of duration t. Centers of neighboring weak coherent states in a group are separated by a time T1, with T1 greater than t. Centers of neighboring weak coherent states in adjacent quantum systems are separated by a time T2, with T2 greater than t. In addition, any two weak coherent states separated by T1+T2 are phase coherent. The receiver station comprises an optical subsystem configured to check, for received quantum systems, phase coherence of two weak coherent states of time bins separated by T1+T2.