Kerr-effect-based quantum logical gates in decoherence-free subspace

Abstract

Efficient implementations of two (or three) qubit logical gates are critical for the large-scale realization of quantum computation in decoherence-free subspace (DFS) immune to the influence of decoherence effect. In this paper, we propose some schemes for setting up a family of quantum control gates, including controlled-NOT (CNOT), Toffoli, and Fredkin gates for two or three logical qubits by means of cross-Kerr nonlinearities in DFS. These three logical gates require neither complicated quantum computational circuits nor auxiliary photons (or entangled states). The success probabilities of three logical gates are approximate unit by performing the corresponding classical feed-forward operations based on the different measuring results of the X homodyne detectors, and their fidelities are robust against the photon loss with the current technology.The proposed logical gates rely on only simple linear-optics elements, available single qubit operations, and mature measurement methods, making our proposed gates be feasible and efficient in practical applications.Comment: 11 pages, 9 figure