Dr. D.M. Segal, Prof. E.A. Hinds, and Prof P.L. Knight.
Imperial College, which is part of the University of London, is one of the highest-rated institutions in the UK academic community. In the recent UK Research Assessment Exercise it was rated second in the country. The Department of Physics, which has around 70 academic staff, gained the top research grade of 5*. Within the Department of Physics there are nine research groups, of which one is the Quantum Optics and Laser Science (QOLS) group. QOLS experimental research covers experimental high intensity physics; laser development; laser spectroscopy and quantum optics; and ion trapping and cooling. There is also an active theoretical group working in theoretical quantum optics, quantum computation, and laser theory. In a very recent development, the experimental group of Prof. E.A. Hinds, lately of the University of Sussex, has moved to Imperial College and was installed by the time this project began.
The ion trap group within QOLS has been working on laser spectroscopy and laser cooling of trapped ions for many years, especially in Penning traps. The team has developed non-invasive spectroscopic techniques for measuring the oscillation frequencies and studying the dynamics of ions in a trap. Studies have also been made of the combined trap and a new variant, the linear combined trap.
Sympathetic cooling of atomic and molecular ions by laser-cooled ions has been investigated. Recent experimental work includes studies on single laser-cooled ions. Theoretical and computational studies of laser cooling in the Penning trap have been made. The team has earlier experience of classical and laser spectroscopy of various atomic and molecular systems.
Current work is mainly concerned with the dynamics of ions in Penning traps, and with the potential use of trapped ions in a Penning trap for quantum information processing. We have recently demonstrated successful axialization of laser-cooled ions, where the high efficiency of laser cooling of the cyclotron motion is extended to the magnetron motion. We are setting up an experiment to investigate decoherence processes in single ions of Ca in the trap and have performed laser cooling of calcium ions in a Penning trap for the first time.
Past achievements of the theory part of the Imperial College London group include a detailed study of the effects of decoherence on ion trap quantum computers, and especially the limitations these place on Shor's factorisation algorithm, and a detailed study of the use of entanglement as a resource in quantum information processing. We have developed quantum Monte Carlo jump techniques to describe the open systems dynamics of individual quantum systems. More recently we have worked on the theory of decoherence free subspaces: an idea being taken up by the Max-Planck experimental group as part of this project.
The theory part of the Imperial College team have close links with other partners in this proposal which will be greatly enhanced by this IST action. In particular, we will interact with the other ion trap and atom trap experimentalists on quantifying decoherence in their gate systems. We will also be providing new theoretical ideas in collaboration with the other theory groups here (including Ulm and Innsbruck with whom we have a proven track record in joint research). The group in Bratislava have a special role in this: they are experts in quantum state reconstruction using maximum entropy concepts; we have a long record of joint publications with this group, where we provide the quantum optics expertise and they provide the expertise on reconstruction issues.
Over the past 5 years, the possibility has emerged of a new technology based on the controlled flow and interaction of cold atoms above microfabricated structures on a surface. The Sussex group (now moved to Imperial College) made some of the key advances that have brought us to this point in cold atom manipulation: we are viewed as being among the leaders in this field. We demonstrated the first magnetic reflector for atoms using a microscopic magnetic pattern recorded on audiotape, which was subsequently developed into an exceedingly high-quality curved mirror based on videotape. This mirror is able to perform high-quality geometrical optics using atoms instead of light.
Remarkably, the videotape can be made compatible with 10-12 torr vacuum if it is properly cleaned. We have also shown that corrugations of the magnetic mirror, introduced by a uniform external bias field, can be used for atom trapping and manipulation and we have developed methods for loading cold atoms and Bose Einstein condensates into microscopic traps and guides on the tape, with a view to quantum information processing.
In parallel with this development our group at Sussex also demonstrated one of the first microscopic atom guides. Our original guide used 4 wires within holes along the length of a small glass fibre made by the Southampton Optoelectronics Research Centre. Now we have a 2-wire version that is currently being developed in our laboratory as a tool for preparing and manipulating small Bose-Einstein condensates. This will be the basis of a sensitive, compact atom interferometer devised by us. Our group reviewed the early developments in this field and subsequent advances are outlined in a Physics World feature article, which gives a popular account of atom chips.
The Hinds' group was previously part of the ACQUIRE FET network on atom chips and remains an associate member of the new project called ACQP. While our expertise fits well with ACQP, we also have a strong history in the field of cavity QED - a major theme of QGates. This attracted us to QGates, within which we intend to realise cavity QED on atom chips. We bring to QGates the expertise it needs to compare atom chip ion trap and optical realisations of quantum gates. There is no question of the EU paying twice for the same research as our affiliation with ACQP is at no cost.
Our group at Imperial College is the co-ordinating institution for the QUBITS network on quantum information processing in atomic systems (Dr. D.M. Segal is the financial coordinator, Prof. P.L. Knight is the scientific coordinator), and we are also a member of the QUEST IHP network. We are part of the HITRAP network on the physics of highly charged ions. Prof. E.A. Hinds' group are involved in the ACQUIRE, Nanofab, a new RTN on Cold Molecules: Formation Trapping and Dynamics.
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