Scalability of atomic-physics based approaches to quantum computing
Abstract
Quantum computers offer two things: a rich array of physical phenomena which can probe basic questions in quantum physics, and the prospect of very powerful computing. However, it is acknowledged that the latter prospect will only be realised if scalable computers can be made, that is, devices whose precision and speed do not decrease too rapidly as the number of qubits increases, especially in the region of hundreds to thousands of qubits. At present that regime is far from achievable in any system, but an intense effort is underway to discover systems with the most promise of reaching it. The great advantages of atomic-physics based approaches are the starting point of the most precisely controlled and least decohering qubits (nuclear spins of quasi-free atoms), and the relative simplicity of the physical system, which allows the most complete knowledge of its behaviour. When quantum gates were demonstrated in trapped ions in 1995, it was not clear whether these advantages could be scaled to many qubits, but in the past few years several proposals have been put forward which allow scalable computers based on arrays of electromagnetically confined atoms or ions manipulated by laser beams. These proposals are among the most fully argued and analysed which exist (in any field of physics) for the realisation of quantum devices which could out-perform classical computers on significant computational problems. The presentation will outline the proposals. Two rely on the concept of an atom- or ion-`chip', i.e. an array of microfabricated atom- or ion-traps, for general-purpose quantum computing. A third system based on an optical lattice is naturally suited to cellular automaton-like computing, and to a new concept of measurement-driven evolution. Common themes in all three are the achievement of precise and multiply-parallel operation of gates between non-neighbour qubits by transporting the atoms, which preserves the nuclear spin state, and manipulation of qubits by photonic rather than electronic methods, which reduces the impact of electronic noise.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2002
- Bibcode:
- 2002APS..MAR.G6001S