Trapped Ion Quantum Computing using Optical Tweezers and the Magnus Effect

Abstract

We consider the implementation of quantum logic gates in trapped ions using tightly focused optical tweezers. Strong polarization gradients near the tweezer focus lead to qubit-state dependent forces on the ion. We show that these may be used to implement quantum logic gates on pairs of ion qubits in a crystal. The qubit-state dependent forces generated by this effect live on the plane perpendicular to the direction of propagation of the laser beams opening new ways of coupling to motional modes of an ion crystal. The proposed gate does not require ground state cooling of the ions and does not rely on the Lamb-Dicke approximation, although the waist of the tightly focused beam needs to be comparable with its wavelength in order to achieve the needed field curvature. Furthermore, the gate can be performed on both ground state and magnetic field insensitive clock state qubits without the need for counter-propagating laser fields. This simplifies the setup and eliminates errors due to phase instabilities between the gate laser beams. Finally, we show that imperfections in the gate execution, in particular pointing errors < 30 nm in the tweezers reduce the gate fidelity from F 0.99998 to 0.999.

Die Anfänge des Frauenstudiums an der Johannes Gutenberg-Universität Mainz

“…In the context of trapped-ion quantum computing, vortex beams can be applied to realize optimized quantum gates with minimized parasitic Stark shifts and off-resonant scattering. In particular, vortex beams can efficiently generate state-dependent optical forces transverse to the beam propagation direction Mazzanti et al [2023], which can allow for increased versatility of optical addressing schemes operating on linear Coulomb crystals. For many trapped-ion qubit realizations, single-and multi-qubit gates are realized via two-photon Raman transitions mediated by off-resonant E1 electric dipole transitions.…”