Universitè De Genève

Kabushiki Kaisha Topcon

Id Quantique Sa

Swisscom Ag

Orbisphere Laboratories Neuchatel Sa

Universrité De Geneve

Nicolas Gisin

Hugo Zbinden

Grégoire Ribordy

Nobuo Hori

Patrick Stamp

Bruno Sanguinetti

Anthony Martin

Karin Julliard

Shigenori Nagano

Olivier Guinnard

Jean-Paul Pellaux

Beat Perny

Antonio Acin

Valerio Scarani

Antoine Muller

Bruno Huttner

Rogerio Passy

Gregoire Ribordy

A device for random number generation based on an optical process of quantum nature, including a light source emitting photons randomly, a light detector adapted to absorb the randomly emitted photons and to measure a number n of photons produced by the light source in a time interval T, and a randomness extractor. The detector includes a photon sensor acting as a photon-to-electron converter, an amplifier for converting the electron signal received from the photon sensor into a voltage and amplifying the voltage signal, as well as an analog-to-digital converter for processing the amplified signal received from the amplifier by encoding the amplified signal into digital values and sending these digital values to the randomness extractor for further processing such as to produce quantum random numbers (QRNs) based on the number of photons produced by the light source in a time interval T.

Method and device for optics based quantum random number generation

An apparatus and method for implementing a secure quantum cryptography system using two non-orthogonal states. For each qubit, the emitter station prepares a quantum system in one of two non-orthogonal quantum states in the time-basis to code bit values. Intra- and inter-qubit interference is then used to reveal eavesdropping attempts. Witness states are used to help reveal attacks performed across the quantum system separation.

Two non-orthogonal states quantum cryptography method and apparatus with intra- and inter-qubit interference for eavesdropper detection

An apparatus and method for implementing a secure quantum cryptography system using two non-orthogonal states. For each qubit, the to emitter station prepares a quantum system in one of two non-orthogonal quantum states in the time-basis to code bit values. Intra- and inter-qubit interference is then used to reveal eavesdropping attempts. Witness states are used to help reveal attacks performed across the quantum system separation.

Two non-orthogonal states quantum cryptography method and apparatus with inter-and inter-qubit interference for eavesdropper detection

An apparatus and method for implementing a quantum cryptography system that requires fewer random bits. The emitter divides the key in blocks of bits. Instead of changing the basis for each bit of key sent by the emitter, the same basis is used for all the bits within a block. By doing this, the rate of random bits of information necessary for the implementation of a secure quantum cryptography link is reduced.

Quantum cryptography with fewer random numbers

In a method and apparatus for synchronizing the receiver and the emitter in an autocompensating quantum cryptography system it is allowed to one of the stations (for example the emitter) to define the timing of all its operations (for example the application of a signal onto the modulator used to encode the values of the bits) as a function of a time reference. This time reference can either be transmitted using a channel from the other station (for example the receiver). It can also consist of a time reference synchronized with that of the other station through using information transmitted along a channel and a synchronization unit. Preferably a time reference unit is provided at each station. One of these time reference units functions as a master, while the other one function as a slave. The slave is synchronized with the master using information transmitted over a communication channel by a synchronization unit.

Method and apparatus for synchronizing the emitter and the receiver in an autocompensating quantum cryptography system

An apparatus and method for implementing a quantum cryptography system encoding bit values on approximations of elementary quantum systems with provable and absolute security against photon number splitting attacks. The emitter encodes the bit values onto pairs of non-orthogonal states belonging to at least two sets, and such that there does not exist a single quantum operation allowing to reduce the overlap of the states in all the sets simultaneously.

Quantum cryptography protocol

A system and method for communicating a key between two stations using an interferometric system for quantum cryptography. The method includes sending at least two light pulses over a quantum channel and detecting the interference created by the light pulses. The interfering pulses traverse the same arms of an interferometer but in a different sequence such that the pulses are delayed when traversing a quantum channel. The pulses are reflected by Faraday mirrors at the ends of the quantum channel so as to cancel any polarization effects. Because the interfering pulses traverse the same arms of an interferometer, there is no need to align or balance between multiple arms of an interferometer.

Quantum cryptography device and method

A method and apparatus for determining the concentration of a substance of interest by gas-coupled photoacoustic spectroscopy (GC-PAS) with an essentially monochromatic beam of radiation in an optical portion of the electromagnetic spectrum; the radiation is selected so as to be absorbed by the substance of interest and the beam is modulated at a sonic frequency which is sufficiently high for generating a primary signal that depends upon the absorption coefficient of the substance of interest as well as upon parameters of operating the method; in order to compensate for these operating parameters, the beam is additionally modulated at a sonic frequency which is sufficiently low for generating a secondary signal which does not depend upon the absorption coefficient of the substance of interest, but, depends only upon parameters of operating the method; a ratio of the first and the second signal is obtained to generate a compensated signal for determining the concentration of the substance of interest.

Spectroscopic method and apparatus

The present invention concerns a method and a device for measuring polarization dispersion of an optical fiber which is particularly useful in telecommunications, and which has a finer resolution of this measurement in comparison to methods and devices known in the art. The device consists of an interferometer (51), a low coherent light source (16), a detector (25) for generating an interferogram, and a module (52) connected in series with the optical fiber to be measured (20), this module comprising a high dispersion birefringent fiber (53) of stable, known polarization, two pairs of fiber bundles (55, 56) for adjusting the polarization controller (54) and for aligning the principal polarization modes of the optical fiber to be measured and the birefringent fiber, and an electronic processor (21) for measuring the separation of the lateral peaks on the interferogram resulting as a function of predetermined adjustments to the polarization controller. The polarization dispersion of the fiber to be measured is deduced by measuring the different separation values.

Method and device for measuring polarization dispersion of an optical

An optical waveguide portion is provided on one surface of a substrate portion. A luminous flux for measurement is caused to be incident on one end face of the optical waveguide substrate, and only leaking light having passed through the substrate portion is received. The cross-sectional distribution of the refractive index of the optical waveguide portion is measured from changes in the received quantity of light.

Apparatus for measuring cross-sectional distribution of refractive index

According to the present invention, there are provided a projection system for emitting luminous flux for measurement, a light receiving unit or a prism member furnished with a light receiving unit, and an optical waveguide substrate comprising a substrate portion and an optical waveguide portion formed on the substrate portion, the light receiving unit or the prism is brought into close contact with the optical waveguide substrate, luminous flux for measurement from the projection system is passed from one end of the optical wavegide portion and a part of the luminous flux for measurement is leaked toward the light receiving unit, whereby cross-sectional distribution of refractive index of the optical waveguide is measured by change of light quantity of the leaking light sensed at the light receiving unit in case an incident point of the luminous flux for measurement is moved.

According to the present invention, there are provided a projection system having an optical axis inclined toward one end surface of an optical waveguide portion arranged on one side of a substrate portion and for irradiating luminous flux for measurement from one end surface of the optical waveguide portion, and a light receiving unit for receiving luminous flux leaking from the optical waveguide portion among the luminous fluxes for measurement, projected light is effectively utilized for measurement, whereby cross-sectional distribution of refractive index of the optical waveguide is measured by change of light quantity entering said light receiving unit in case an incident point of the luminous flux is moved.

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Vessy, Switzerland

Nicolas Gisin