Qinetiq Limited

Qubitekk, Inc.

Brian Sinclair Lowans

Simon Robert Wiseman

Ewan David Finlayson

Richard Middleton Hicks

Stephen Gerard Ayling

Richard Michael Jenkins

Meirion F Lewis

John M Heaton

Rebecca Anne Wilson

Philip Michael Gorman

Michael J Kane

Richard Andrew Oak

John Michael Heaton

Michael John Kane

Methods and apparatus for quantum key distribution are described, in particular including methods and networksarranged to improve and/or ensure the security of data transmitted thereby by (i) ensuring a certain level of loss within at least part of the network, (ii) placing a penultimate and an endpoint nodes in situated in a secure second enclave, (iii) analyzing a transmitted bit stream to ensure that it does not provide an unacceptable amount of information about the key that may be generated therefrom, and/or (iv) varying the order in which bits are used to generate a key.

Quantum key distribution

An optical receiver for a quantum key distribution system comprises a plurality of optical components mounted or formed in a substrate and optically coupled by one or more hollow core waveguides formed in the substrate.

Optical transmitters and receivers for quantum key distribution

This invention relates to an optical star network in which different communities of users, such as different businesses, are provided through use of quantum key distribution (QKD). At least one QKD device is located at the central hub of the star network and communicates with QKD devices at the endpoints to establish a separate quantum key, i.e. a cryptographic key established by QKD, with each endpoint. A separate key manager is provided for each different community and each key manager is arranged to use the appropriate quantum keys for endpoints within that community to deliver the same community key to each endpoint. This community key can be used by for encrypting network traffic between members of the same community with security. Traffic passing through the network switch is encrypted, but the community keys are not delivered via the switch and hence the switch an error in the switch does not compromise security.

Multi-community network with quantum key distribution

The method involves exchange of a quantum signal between a first quantum node and a second quantum node as is usual in known quantum key distribution (QKD) scheme. The first quantum node communicates details of the quantum signal it sent or received with a first remote node. The first remote node thus has all the information to required to take the place of the first quantum node in the key agreement step with the second quantum node. The first quantum node may be arranged to transmit the quantum signal to the second quantum node, in which case the invention provides a distributed quantum transmitter with the control logic in the first remote node being distributed remotely from the actual quantum transmitter in the first quantum node. Communications between the first remote node and first quantum node may comprise or be protected by a quantum key derived by conventional QKD.

Quantum cryptography apparatus

The present invention relates to an improved quantum signal transmitter, which has a plurality of quantum output channels having at least one optical source and at least one optical splitter acting on the output of said at least one source. Such a transmitter can easily be used with existing passive optical network (PON) systems and can be a compact piece of equipment.

Multiplexed quantum key distribution

A method of establishing a quantum key for use between a first network node (QNode) and a second network node (QNode) in a network for carrying out quantum cryptography includes a key agreement step carried out by a third node (QNode) and the second node (QNode) and a subsequent authentication step carried out by the first and second nodes directly. As the key agreement step does not involve QNode, another key agreement step may be simultaneously performed by another pair of network nodes QNode, QNodeto agree a quantum key for use by network nodes QNodeand QNode. The invention allows respective quantum keys to be established between a network node and each of a set of other nodes more rapidly than is the case if each quantum key is established serially by key agreement and authentication steps.

Method of establishing a quantum key for use between network nodes

Methods and apparatus for use in quantum key distribution (QKD) are described. A quantum QKD signal is generated at a source and transmitted through a fiber optic network to an endpoint, a key being agreed with communication over a classical QKD channel. The classical QKD channel contains additional information relevant to a network over which keys are distributed, and may be processed at nodes intermediate between the source and the endpoint.

Methods and apparatus for use in quantum key distribution

A method of performing quantum key distribution across a network. The method involves a first node first agreeing a quantum key with a first intermediate node in the path. Next the intermediate node exchanges a quantum signal with the next node in the path&#x2014;which is a targeted node. The intermediate node communicates with the first node using the previous established quantum key details of the quantum signal sent or received by the intermediate node. The first node then performs a key agreement step to agree a quantum key directly with the targeted node. Having established a quantum key with the current targeted node the method can be repeated but with the next node in the network path as the targeted node until a destination node is reached. The final quantum key agreed with the destination node can then be used for encrypting communication between those nodes across the network.

Network having quantum key distribution

The invention relates to methods and apparatus for Quantum key distribution. Such methods including authenticating a first node in a communications network with a remote node in the communications network. The authentication may include connecting an authentication device to the first node, agreeing a quantum key between the first node and the remote node based on a quantum signal transmitted or received by the first node and performing an authentication step between the authentication device and the remote node on an encrypted channel. Authentication between the authentication device and remote node may be taken as authentication of the first node.

An electro-optic waveguide polarization modulator () comprising a waveguide core () having first and second faces defining a waveguide core plane, a plurality of primary electrodes () arranged at a first side of the waveguide core plane and out of said plane, and at least one secondary electrode () arranged at a second side of the waveguide core plane and out of said plane, wherein the electrodes () are adapted in use to provide an electric field having field components () in two substantially perpendicular directions within the waveguide core () so as modulate the refractive index thereof such that electromagnetic radiation propagating through the core () is converted from a first polarization state to a second polarization state.

Electro-optic waveguide polarisation modulator

An apparatus for detecting the presence of one or more images of a known kind in a scene is disclosed which comprises a digital input means and an optical output means. The digital input means comprises a capture means which passes a capture image to a first electronic processing means to produce a scene pattern corresponding to a Fourier Transform of the scene image. This pattern is then digitally combined with one or more reference patterns corresponding to Fourier Transforms of a reference image. The resulting combined patterns are then used to modulate a beam of light which may be focused to perform an inverse Fourier Transform providing correlation information. In a preferred embodiment, the combined pattern is displayed on a spatial light modulator. A 'smart' spatial light modulator is also disclosed which comprises an array of light modulating devices, each device comprising a detector and at least one pixel, whereby light incident upon the detector produces an output signal which is adapted to control the state of the modulating medium. By suitable processing, the 'smart' SLM may be adapted to either attenuate light below a certain intensity or only light above a certain intensity to act as a saturable absorber.

Method and apparatus for detecting the presence of one or more images of a known predetermined kind of scene

An imaging system () has a fixed lens combination (), a spatial light modulator (SLM) () and a linear detector array (). A scene image is scanned across a simple array () in a direction perpendicular to the array () by the SLM (). This is achieved by displaying a diffraction pattern on the SLM that changes to achieve the scanning. The diffraction pattern displayed typically has a linear element () and a quadratic element (42). By having a programmably changed combined chirp pattern () displayed on the SLM, and by being able to change it thousands of times a second, an army with fast read out can take the place of a 2-D imaging array.

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Malvern, United Kingdom

Brian Sinclair Lowans