Marshall Stoneham, London Centre for Technology, and Department of Physics and Astronomy, University College London
New ideas lead to new technologies, and new technologies demand new materials. Silicon technology spawned a whole series of materials innovations: functional materials like ultra-pure silicon and copper interconnets; passive materials for heat sinks and diffusion barriers; new materials for fabrication, like photoresists; novel fabrication, like ion implantation, and so on. Quantum information processing (QIP), a radical new technology, will demand a new list of materials. So what are these needs? Can QIP operate alongside existing silicon and photonic technologies, in a way that is silicon-compatible? Could key devices should be manufacturable in a near-future generation fabrication plant? Many methods needed to fabricate and run these devices have been used somewhere in the world, but aren’t “on every shelf.”
Quantum ideas may be radical, but their impact depends on whether they are useable. Materials science provides limits, with challenges of manufacturing, of characterising devices, and - perhaps hardest of all - integrating the quantum device with the classical components that we all use. QIP must work alongside standard systems, with standard silicon technology to run them and ideally integrated with optical networks.
Will a quantum computer work? Probably yes. Could a QIP device operate at room temperature? Probably yes, but there are formidable difficulties. Could a QIP device be as portable as a laptop? Perhapsyes, but that is less clear. Since there is no major QIP industry, how useful might be even an inexpensive room-temperature quantum processor? Ideas mooted include the probable (demonstrated at a modest scale, like factorisation or directory searches), the possible (proven potential, e.g., designing a better quantum computer), or the conceivable (hard computational problems like turbulence, to appeal to chemical engineers and aero engine designers). A more likely first use will be frivolous (quantum games), just as new materials are found in golf clubs long before advanced technology applications. Nor should one forget ideas not yet conceived: the solid-state laser was a solution without a problem for two decades prior to the compact disc. And will a quantum computer avoid those problems of standard computers that drive us paranoid? That must be science fiction - just think about about re-booting a quantum computer.
(The above is a brief summary for the LCN Website of the paper by Marshall Stoneham 2008 "The Quantum in your Materials World" Materials Today 11 (9) 32-36)
Fig. 1 Flying and static qubits. The patches might be linked by flying qubits to form some larger processor, in this case a two-dimensional array, perhaps exploiting electrons in image states above a negative electron affinity layer.
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About the London Centre for Nanotechnology
The London Centre for Nanotechnology is an interdisciplinary joint enterprise between University College London and Imperial College London. In bringing together world-class infrastructure and leading nanotechnology research activities, the Centre aims to attain the critical mass to compete with the best facilities abroad. Research programmes are aligned to three key areas, namely Planet Care, Healthcare and Information Technology and bridge together biomedical, physical and engineering sciences. Website: www.london-nano.com