The effects of water impinging on thermally controlled surfaces under space conditions

Analysis of monochromatic reflectance changes due to impinging water spray from sharp-edge nozzles on thermally-controlled paints under space condition

The quantum-classical crossover of a field mode

We explore the quantum-classical crossover in the behaviour of a quantum field mode. The quantum behaviour of a two-state system - a qubit - coupled to the field is used as a probe. Collapse and revival of the qubit inversion form the signature for quantum behaviour of the field and continuous Rabi oscillations form the signature for classical behaviour of the field. We demonstrate both limits in a single model for the full coupled system, for states with the same average field strength, and so for qubits with the same Rabi frequency.Comment: 6 pages, 3 figures (in this version the figures, text and references have all been expanded

Signatures of the collapse and revival of a spin Schr\"{o}dinger cat state in a continuously monitored field mode

We study the effects of continuous measurement of the field mode during the collapse and revival of spin Schr\"{o}dinger cat states in the Tavis-Cummings model of N qubits (two-level quantum systems) coupled to a field mode. We show that a compromise between relatively weak and relatively strong continuous measurement will not completely destroy the collapse and revival dynamics while still providing enough signal-to-noise resolution to identify the signatures of the process in the measurement record. This type of measurement would in principle allow the verification of the occurrence of the collapse and revival of a spin Schr\"{o}dinger cat state.Comment: 5 pages, 2 figure

Cool for Cats

The iconic Schr\"odinger's cat state describes a system that may be in a superposition of two macroscopically distinct states, for example two clearly separated oscillator coherent states. Quite apart from their role in understanding the quantum classical boundary, such states have been suggested as offering a quantum advantage for quantum metrology, quantum communication and quantum computation. As is well known these applications have to face the difficulty that the irreversible interaction with an environment causes the superposition to rapidly evolve to a mixture of the component states in the case that the environment is not monitored. Here we show that by engineering the interaction with the environment there exists a large class of systems that can evolve irreversibly to a cat state. To be precise we show that it is possible to engineer an irreversible process so that the steady state is close to a pure Schr\"odinger's cat state by using double well systems and an environment comprising two-photon (or phonon) absorbers. We also show that it should be possible to prolong the lifetime of a Schr\"odinger's cat state exposed to the destructive effects of a conventional single-photon decohering environment. Our protocol should make it easier to prepare and maintain Schr\"odinger cat states which would be useful in applications of quantum metrology and information processing as well as being of interest to those probing the quantum to classical transition.Comment: 10 pages, 7 figures. Significantly updated version with supplementary informatio

Mental imagery in synaesthesia

The current thesis addressed the question of whether an internally generated mental image can elicit a concurrent in grapheme colour synaesthesia; although there is experimental and anecdotal evidence that this is the case, to date this had not been systematically explored. As there are purportedly distinct object-based and spatial-based imagery processes it was necessary to explore the role different imagery processes may play. In Experiment 1 synaesthetes and matched control groups completed a grapheme-based object-imagery task against congruently and incongruently coloured backgrounds. Four synaesthetes, but none of the control groups, showed an effect of colour on task performance. In Experiment 2 and 3 synaesthetes (and matched controls for Experiment 2) completed a grapheme-based spatial-imagery task, with either the stimuli or background colour manipulated as before. In each experiment colour was found to interact with grapheme presentation format for two different synaesthetes. Experiments 1-3 therefore provided support for the idea that an internally generated mental image can elicit a concurrent. Importantly, the results suggested a difference in the way the concurrent generated from object or spatial imagery processes influenced task performance. Consequently Experiments 4 and 5 used a battery of comparable imagery tasks that had either an object or spatial rate-limiting imagery process. Manipulation of the task background colour again showed the variety of effects the concurrent generated with these different imagery processes can have on task performance. Overall the results of these experiments suggest that a concurrent can be elicited from both object and spatial imagery processes; important individual differences were found, and individual performance varied between tasks, suggesting the possible role of strategy effects. Models of synaesthesia need to be able to explain these differences and further studies are needed to address this issue of task approach

Freezing distributed entanglement in spin chains

We show how to freeze distributed entanglement that has been created from the natural dynamics of spin chain systems. The technique that we propose simply requires single-qubit operations and isolates the entanglement in specific qubits at the ends of branches. Such frozen entanglement provides a useful resource, for example for teleportation or distributed quantum processing. The scheme can be applied to a wide range of systems -- including actual spin systems and alternative qubit embodiments in strings of quantum dots, molecules or atoms.Comment: 5 pages, to appear in Phys. Rev. A (Rapid Communication