Centre National De La Recherche Scientifique

Thales

UniversitÉ Libre De Bruxelles

Le Centre National De La Recherche

Groupe Des Ecoles De Télécommunications - Ecole Nationale Supérieure Des Télécommunications

Philippe Grangier

Gilles Van Assche

Thierry Debuisschert

Jérôme Charles Wenger

Nicolas Cerf

Frédéric Grosshans

Jerome Lodewyck

Rosa Tualle-Brouri

Rosa Brouri-Tualle

Anthony Leverrier

A continuous variable quantum encryption key distribution system comprises a sender (Alice) able to randomly choose the phase and the amplitude of each coherent light pulse of a signal, to provide a coherent state defined by a first quadrature and a second quadrature that are random, and to transmit to a receiver (Bob) the signal pulses (S) and a local oscillator (LO), the receiver comprising a homodyne detector () for measuring a randomly chosen quadrature of a signal pulse. The sender comprises a device for time-division multiplexing the pulses of the signal (S) and of the local oscillator (LO) to handle the transmission over an optical fiber () of the signal and local oscillator pulses to the receiver. The receiver comprises a demultiplexer (), able to send the received pulses over a first channel (), or over a second channel (). The channels are applied as inputs to the homodyne detector (). One of the first and second channels includes a phase modulator (), enabling a random selection by the homodyne detector of a quadrature from the first and the second quadratures of a coherent state of a signal pulse. A delay line (), is used for resynchronizing the signal and local oscillator pulses.

Continuous variable quantum encryption key distribution system

One aspect of the present invention is related to a quantum cryptographic scheme comprising at least one sending unit including a physical means of encoding and distributing a raw key in the quadrature components of quantum coherent states that are continuously modulated in phase and amplitude, at least one receiving unit containing a physical means of performing homodyne detection of the quantum coherent states in order to measure the quadrature components of the states, a quantum channel for connecting the sending unit to the receiving unit, a two-way authenticated public channel for transmitting non-secret messages between the sending unit and the receiving unit, a quantum key distribution protocol ensuring that the information tapped by a potential eavesdropper can be estimated from the quantum channel parameters, and a direct or reverse reconciliation protocol that converts the raw continuous data into a common binary key.

High-rate quantum key distribution scheme relying on continuously phase and amplitude-modulated coherent light pulses

Growing community of inventors

Saint Rémy les Chevreuse, France

Philippe Grangier