Faster quantum computation with permutations and resonant couplings. (arXiv:1901.00252v2 [quant-ph] UPDATED)

Recently, there has been increasing interest in designing schemes for quantum
computations that are robust against errors. Although considerable research has
been devoted to developing quantum error correction schemes, much less
attention has been paid to optimizing the speed it takes to perform a quantum
computation and developing computation models that act on decoherence-free
subspaces. Speeding up a quantum computation is important, because fewer errors
are likely to result. Encoding quantum information in a decoherence-free
subspace is also important, because errors would be inherently suppressed. In
this paper, we consider quantum computation in a decoherence-free subspace and
also optimize its speed. To achieve this, we perform certain single-qubit
quantum computations by simply permuting the underlying qubits. Together with
exchange-interactions or Ising-interactions and other resonant couplings, we
present a new scheme for quantum computation that potentially improves the
speed in which a quantum computation can be done.

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