Hewlett-Packard Development Company, L.p.

Other

Cambridge Quantum Computing Limited

Adrian P Kent

Raymond G Beausoleil

William John Munro

Timothy Paul Spiller

Richard Stanley Williams

Philip John Kuekes

Secure, semi-classical authentication schemes are presented. An authentication token is generated by applying a pre-determined measurement to a plurality of random quantum states to obtain a sequence of classical measurement outcomes. The token is validated by receiving the classical measurement outcomes and verifying whether the sequence corresponds to a statistically plausible result for the pre-determined measurement of the plurality of quantum states.

Quantum tokens

A method of establishing a shared secret random cryptographic key between a sender and a recipient using a quantum communications channel is described. The method comprises: generating a plurality of random quantum states of a quantum entity, each random state being defined by a randomly selected one of a first plurality of bases in Hilbert space, transmitting the plurality of random quantum states of the quantum entity via the quantum channel to a recipient, measuring the quantum state of each of the received quantum states of the quantum entity with respect to a randomly selected one of a second plurality of bases in Hilbert space, transmitting to the recipient composition information describing a subset of the plurality of random quantum states, analysing the received composition information and the measured quantum states corresponding to the subset to derive a first statistical distribution describing the subset of transmitted quantum states and a second statistical distribution describing the corresponding measured quantum states, establishing the level of confidence in the validity of the plurality of transmitted random quantum states by verifying that the first and second statistical distributions are sufficiently similar, deriving a first binary sting and a second binary string, correlated to the first binary string, respectively from the transmitted and received plurality of quantum states not in the subset, and carrying out a reconciliation of the second binary string to the first binary string by using error correction techniques to establish the shared secret random cryptographic key from the first and second binary strings.

Quantum cryptography

Quantum information processing structures and methods use photons and four-level matter systems in electromagnetically induced transparency (EIT) arrangements for one and two-qubit quantum gates, two-photon phase shifters, and Bell state measurement devices. For efficient coupling of the matter systems to the photons while decoupling the matter systems from the phonon bath, molecular cages or molecular tethers maintain the atoms within the electromagnetic field of the photon, e.g., in the evanescent field surrounding the core of an optical fiber carrying the photons. To reduce decoherence caused by spontaneous emissions, the matter systems can be embedded in photonic bandgap crystals or the matter systems can be selected to include metastable energy levels.

Quantum information processing using electromagnetically induced transparency

A security system uses a source capable of producing an entangled state of a sensing mode and a reference mode. The sensing mode has a path that enters an area around an object being secured. A state measurement system in the security system can measure a combination of the sensing mode after traversal of the sensing path and the reference mode after traversal of a reference path.

Security systems and monitoring methods using quantum states

A method of verifying the position of a tagging device is described. The method comprises: storing response information in a quantum state of a quantum entity, the quantum entity comprising an entangled pair; separating the entangled pair into first and second entangled particles; conveying the first and second entangled particles to first and second emitters respectively; emitting the first and second particles of the entangled pair respectively from the first and second emitters to the tagging device; recombining the first and second entangled particles in the tagging device to determine the response information; transmitting a signal from the tagging device to at least one of a plurality of detectors; recording the arrival time of the signal at the or each receiving detector, the or each receiving detector being selected on the basis of the determined response information; and comparing the or each receiving detector and the arrival time of the signal at the or each receiving detector with at least one expected receiving detector and an expected arrival time of the signal for the or each expected receiving detector. Matching the expected and actual signal arrival time for an expected detector verifies the position of the tagging device.

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Bristol, United Kingdom

Adrian P Kent