Abstract
In ion traps, entangling gate operations can be realized by a bichromatic pair of laser beams that collectively interact with the ions. In this paper, a new method of modelling the laser–ion interaction is introduced that turns out to be superior to standard techniques for the description of gate operations on optical qubits. The treatment allows for a comparison of the performance of gates based on σz⊗σz and σϕ⊗σϕ interactions on optical transitions where the bichromatic laser field can be realized by an amplitude-modulated laser resonant with the qubit transition. Shaping the amplitude of the bichromatic laser pulse is shown to make the gates more robust against experimental imperfections.
Highlights
The processing of information based on the laws of quantum physics [1] has become a very active field of research during the last decade
Collective laser-ion interactions with bichromatic laser beams are capable of performing both σz⊗σz gates as well as Mølmer-Sørensen gate operations
While the paper was focused on the case of qubit states linked by a weak optical transition, the discussion of the Mølmer-Sørensen gate interaction applies to hyperfine qubits where non-resonant carrier excitation occurs in the limit of fast gate operations
Summary
The processing of information based on the laws of quantum physics [1] has become a very active field of research during the last decade. Solano [12], and subsequently realized by ion trapping groups in Boulder, Ann Arbor and Oxford [3, 4, 5] Even though both classes of gates are applicable to hyperfine qubits as well as optical qubits (i.e. qubits encoded in hyperfine states or in states linked by a dipole-forbidden transition with an optical wavelength), current experiments with optical qubits have relied on the former and experiments with hyperfine qubits on the latter type of interaction.
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