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A silicon-based nuclear spin quantum computer


Quantum computers promise to exceed the computational efficiency of ordinary classical machines because quantum algorithms allow the execution of certain tasks in fewer steps. But practical implementation of these machines poses a formidable challenge. Here I present a scheme for implementing a quantum-mechanical computer. Information is encoded onto the nuclear spins of donor atoms in doped silicon electronic devices. Logical operations on individual spins are performed using externally applied electric fields, and spin measurements are made using currents of spin-polarized electrons. The realization of such a computer is dependent on future refinements of conventional silicon electronics.

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Figure 1: Illustration of two cells in a one-dimensional array containing 31P donors and electrons in a Si host, separated by a barrier from metal gates on the surface.
Figure 2: An electric field applied to an A gate pulls the electron wavefunction away from the donor and towards the barrier, reducing the hyperfine interaction and the resonance frequency of the nucleus.
Figure 3: J gates vary the electrostatic potential barrier V between donors to enhance or reduce exchange coupling, proportional to the electron wavefunction overlap.
Figure 4: Two qubit quantum logic and spin measurement.

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This work has been supported by the Australian Research Council. I thank R.G.Clark for encouragement and E. Hellman for suggesting that the work in ref. 18 could be relevant to quantum computation.

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Correspondence to B. E. Kane.

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Kane, B. A silicon-based nuclear spin quantum computer. Nature 393, 133–137 (1998).

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