Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vaporize an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.

Abstract: A method and apparatus (80) are provided for routing entanglement building between a selected pairing of interface qubits (82). The qubits of the selected pairing of interface qubits (82) are separately entangled with at least one intermediate qubit (84) by interacting respective light fields with the interface qubits of the selected pairing and using an optical merge arrangement (83) to further interact the light fields with at least one intermediate qubit (84). Where there are multiple intermediate qubits (84) the intermediate qubits are entangled with each other. The or each entangled intermediate qubit (84) is then removed from entanglement.

Abstract: A control system for a subsea well is provided. The control system comprises a tree comprising a hydraulic control supply line for use in opening a downhole safety valve as a result of hydraulic pressure in the line. A part of the line is carried by a structure which is subject to the pressure of a production fluid from the well used in the control system so that the line is separable in response to a failure of the integrity of the structure.

Abstract: A method is provided of creating an end-to-end entanglement (87) between qubits in first and second end nodes (81, 82) of a chain of optically-coupled nodes whose intermediate nodes (80) are quantum repeaters. Local entanglements (85) are created on an on-going basis between qubits in neighboring pairs in the chain through interaction of the qubits with light fields transmitted between the nodes. The quantum repeaters (80) are cyclically operated with their top-level operating cycles being synchronized. Once every top-level operating cycle, each repeater (80) initiates a merging of two entanglements involving respective repeater qubits that are at least expected to be entangled with qubits in nodes disposed in opposite directions along the chain from the repeater. A quantum repeater (80) adapted for implementing this method is also provided.

Abstract: An iterative method is provided for progressively building an end-to-end entanglement between qubits in first and second end nodes (91, 92) of a chain of nodes whose intermediate nodes (90) are quantum repeaters. At each iteration, a current operative repeater (90) of the chain merges an entanglement existing between qubits in the first end node (91) and the operative repeater, with a local entanglement formed between qubits in the operative repeater and its neighbor node towards the second end node (92). For the first iteration, the operative repeater is the neighbor of the first end node (91); thereafter, for each new iteration the operative repeater shifts one node further along the chain toward the second end node (92). A quantum repeater adapted for implementing this method is also provided.

Abstract: A control system for a subsea well is provided. The control system comprises a tree comprising a hydraulic control supply line for use in opening a downhole safety valve as a result of hydraulic pressure in the line. A part of the line is carried by a structure which is subject to the pressure of a production fluid from the well used in the control system so that the line is separable in response to a failure of the integrity of the structure.

Abstract: A QKD transmission apparatus comprises a GPS receiver module operable to receive a GPS signal, and a processor operable to use the GPS signal to derive a clock signal for transmission of a QKD signal.

Abstract: A QKD transmission method comprises generating a transmission list for a plurality of data bits, the list comprising a randomized timing schedule defining respective times for transmission of the data bits, providing a clock signal and using the clock signal to initiate the transmission of the data bits at a predetermined time in order to provide a QKD signal, and an apparatus therefor.

Abstract: A processing arrangement of a data communication apparatus is arranged to derive an ordered plurality of modulo-2 summations of respective selections of data bits of a binary data set. The data communication apparatus may either be transmitting apparatus with the processing arrangement serving to determine a target syndrome for subsequent use in error correction, or receiving apparatus with the data processing arrangement being arranged to effect error correction of received data. The processing arrangement effects its selections of bits from the binary data set in accordance with the interconnection of nodes in a logical network of nodes and edges that together define at least a continuum of cells covering a finite toroid. The structuring provided to bit selection by this continuum can be offset by randomness provided by other structures of the network and by the random association of bits of the binary data set with the nodes of the continuum.

Abstract: A QKD transmission apparatus comprises a GPS receiver module operable to receive a GPS signal, and a processor operable to use the GPS signal to derive a clock signal for transmission of a QKD signal.

Abstract: A method and apparatus (80) are provided for routing entanglement building between a selected pairing of interface qubits (82). The qubits of the selected pairing of interface qubits (82) are separately entangled with at least one intermediate qubit (84) by interacting respective light fields with the interface qubits of the selected pairing and using an optical merge arrangement (83) to further interact the light fields with at least one intermediate qubit (84). Where there are multiple intermediate qubits (84) the intermediate qubits are entangled with each other. The or each entangled intermediate qubit (84) is then removed from entanglement.

Abstract: To identify errored bits in a binary data set, an ordered plurality of modulo-2 summations of respective selections of the data-set bits are compared with a target syndrome. The selections of data-set bits are defined by the connection of sum nodes to variable nodes in a logical network of nodes and edges where each variable node is associated with a respective data-set bit and each sum node corresponds to a respective modulo-2 summation. Any sum node for which the corresponding summation of selected data-set bits is found to be inconsistent with the target syndrome is identified as errored. Predetermined patterns of errored sum nodes are then looked for to identify one or more associated errored data-set bits. The identified errored data-set bits can then be flipped to correct them.

Abstract: A method is provided of creating an end-to-end entanglement (87) between qubits in first and second end nodes (81, 82) of a chain of optically-coupled nodes whose intermediate nodes (80) are quantum repeaters. Local entanglements (85) are created on an on-going basis between qubits in neighbouring pairs in the chain through interaction of the qubits with light fields transmitted between the nodes. The quantum repeaters (80) are cyclically operated with their top-level operating cycles being synchronized. Once every top-level operating cycle, each repeater (80) initiates a merging of two entanglements involving respective repeater qubits that are at least expected to be entangled with qubits in nodes disposed in opposite directions along the chain from the repeater. A quantum repeater (80) adapted for implementing this method is also provided.

Abstract: An iterative method is provided for progressively building an end-to-end entanglement between qubits in first and second end nodes (91, 92) of a chain of nodes whose intermediate nodes (90) are quantum repeaters. At each iteration, a current operative repeater (90) of the chain merges an entanglement existing between qubits in the first end node (91) and the operative repeater, with a local entanglement formed between qubits in the operative repeater and its neighbour node towards the second end node (92). For the first iteration, the operative repeater is the neighbour of the first end node (91); thereafter, for each new iteration the operative repeater shifts one node further along the chain toward the second end node (92). A quantum repeater adapted for implementing this method is also provided.

Abstract: In order to facilitate alignment of a QKD transmitter and QKD receiver, the transmitter is provided with a retro-reflector for returning to the receiver a photon beam originating at the latter. The transmitter is arranged to polarization modulate the retro-reflected beam. The transmitter is provided both with an intensity detector for generating an indication of retro-reflected photon intensity, and an intensity-dependent controller for controlling the QKD transmitter in dependence on the detected photon intensity. In one embodiment, this control involves aborting operation of the QKD transmitter upon an unexpectedly high photon intensity being detected; in another embodiment, the intensity indication is used to control the attenuation of the retro-reflected beam so as stabilize the average retro-reflected photon count per unit time.