Encoded Universality in Physical Implementations of a Quantum Computer
D. Bacon, J. Kempe, D. P. DiVincenzo, D. A. Lidar, K. B. Whaley
备注：
6 pages, no figures. To appear in proceedings of the International Conference on Experimental Implementation of Quantum Computation, Sydney, Australia (IQC 01), minor changes, references updated
发表信息：
Proceedings of the 1st International Conference on Experimental Implementations of Quantum Computation, Sydney, Australia, edited by R. Clark (Rinton, Princeton, NJ, 2001), p. 257
We revisit the question of universality in quantum computing and propose a new paradigm. Instead of forcing a physical system to enact a predetermined set of universal gates (e.g., single-qubit operations and CNOT), we focus on the intrinsic ability of a system to act as a universal quantum computer using only its naturally available interactions. A key element of this approach is the realization that the fungible nature of quantum information allows for universal manipulations using quantum information encoded in a subspace of the full system Hilbert space, as an alternative to using physical qubits directly. Starting with the interactions intrinsic to the physical system, we show how to determine the possible universality resulting from these interactions over an encoded subspace. We outline a general Lie-algebraic framework which can be used to find the encoding for universality and give several examples relevant to solid-state quantum computing.
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We propose an effective set of elementary quantum gates which provide an encoded universality and demonstrate the physical feasibility of these gates for the solid-state quantum computer based on the multi-atomic systems in the QED cavity. We use the two-qubit encoding and swapping-based operations to simplify a physical realization of universal quantum computing and add the immunity to a number of errors. This approach allows to implement any encoded single-qubit operation by three elementary gates and the encoded controlled- NOT operation can be performed in a single step. The considerable a…
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