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Laser Physics

Quantum computation based on a quantum switch in cavity QED

Xun‐Li Feng, L. C. Kwek, C. H. Lai, C. H. Oh

Published Oct 30, 2006• 2 citations
Publisher

Abstract

A feasible scheme for constructing quantum logic gates is proposed on the basis of quantum switches in cavity QED. It is shown that the light field which is fed into the cavity due to the passage of an atom in a certain state can be used to manipulate the conditioned quantum logical gate. In our scheme, the quantum information is encoded in the states of Rydberg atoms and the cavity mode is not used as logical qubits or as a communicating “bus”; thus, the effect of atomic spontaneous emission can be neglected and the strict requirements for the cavity can be relaxed.

DOI
10.1134/s1054660x0611003x

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We propose a scheme for realization a quantum Controlled-NOT gate operation using two four-level atoms through a selective atom–cavity interaction in cavity quantum electrodynamics system. In our protocol, the quantum information is encoded on the stable ground states of the two atoms. During the interaction between atoms and single-mode vacuum cavity-field, the atomic spontaneous emission is negligible as the large atom–cavity detuning effectively suppresses the spontaneous decay of the atoms. The influences of the dissipation and the deviation of interaction time on fidelity and corresponding success probability of the quantum Controlled-NOT gate and the experimental feasibility of our proposal are also discussed.
A scheme is proposed to realize a two-qubit quantum phase gate for the intracavity modes. In the scheme, two qubits are encoded in zero- and one-photon Fock states of two intracavity modes, and the three-level $\ensuremath{\Lambda}$-type atom trapped in a high-QQQ cavity mediates the conditional phase gate within a given interaction time. The influence of cavity decay and atomic spontaneous emission on the gate fidelity is also discussed.
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We propose a scheme for realization of three-qubit controlled-phase gate via passing two three-level atoms through a high-Q optical cavity in a cavity QED system. In the presented protocol, the two stable ground states of the atoms act as the two controlling qubits and the zero- and one-photon Fock states of the cavity-field form the target qubit, and no auxiliary state or any measurement is required. The numerical simulation shows that the gate fidelities remain at a high level under the influence of the atomic spontaneous emission, the decay of the cavity mode and deviation of the coupling strength. The experimental feasibility of our proposal is also discussed.