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Physical Review A

Operation of a quantum phase gate using neutral atoms in microscopic dipole traps

Игорь Евгеньевич Проценко, G. Reymond, Nicolas Schlosser, Philippe Grangier

Published Apr 15, 2002• 74 citations
Publisher

Abstract

In this paper we propose and analyze various operating regimes of a quantum phase gate built on two atoms trapped in two independent dipole traps. The gate operates when the atoms are excited using a two-photon transition from the hyperfine manifold of ground states up to Rydberg states with strong dipole-dipole interaction. Experimental requirements are discussed to reach a fast (microsecond) gate operation.

DOI
10.1103/physreva.65.052301

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In this paper we propose and analyze various operating regimes of a quantum phase gate built on two atoms trapped in two independent dipole traps. The gate operates when the atoms are excited using a two-photon transition from the hyperfine manifold of ground states up to Rydberg states with strong dipole-dipole interaction. Experimental requirements are discussed to reach a fast (microsecond) gate operation.
We propose several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential. In our example, the large interaction energy required to perform fast gate operations is provided by the dipole-dipole interaction of atoms excited to low-lying Rydberg states in constant electric fields. A detailed analysis of imperfections of the gate operation is given.
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We present a detailed analysis and design of a neutral atom quantum logic device based on atoms in optical traps interacting via dipole-dipole coupling of Rydberg states. The dominant physical mechanisms leading to decoherence and loss of fidelity are enumerated. Our results support the feasibility of performing single- and two-qubit gates at MHz rates with decoherence probability and fidelity errors at the level of ${10}^{\ensuremath{-}3}$ for each operation. Current limitations and possible approaches to further improvement of the device are discussed.
We study a means of creating multiparticle entanglement of neutral atoms using pairwise controlled dipole-dipole interactions. For tightly trapped atoms the dipolar interaction energy can be much larger than the photon scattering rate and substantial coherent evolution of the two-atom state can be achieved before decoherence occurs. Excitation of the dipoles can be made conditional on the atomic states, allowing for deterministic generation of entanglement. We derive selection rules and a figure of merit for the dipole-dipole interaction matrix elements, for alkali atoms with hyperfine structure and trapped in localized center of mass states. Different protocols are presented for implementing two-qubit quantum logic gates such as the controlled-phase and swap gates. We analyze the error probability of our gate designs, finite due to decoherence from cooperative spontaneous emission and coherent couplings outside the logical basis. Outlines for extending our model to include the full molecular interactions potentials are discussed.