A two-qubit gate in trapped ions using the optical Magnus effect

We present a novel implementation of quantum logic gates in trapped ions using tightly focused optical tweezers [1]. Such tightly focused tweezers exhibit strong a polarization gradient at their focus. This can be used to generate qubit-state dependent forces on trapped ions in order to engineer a novel type of quantum logic gate. Interestingly these forces lay on the plane perpendicular to the direction of propagation of the tweezers that generate them. This greatly simplifies the required optical system and allows for new ways of coupling to motional modes of an ion crystal. We show that the proposed gate does not require ground state cooling in order to achieve high fidelities.

The trapped ions quantum computer has much to gain from the combination with optical tweezers. They can be used to create a programmable quantum simulator [2] as well as a second type of two-qubit logic gate [3] using state dependent optical tweezers in combination with weak oscillating electric fields. By coupling the electric field to the center of mass motion of the whole crystal the proposed gate fidelity is independent on the separation between the targeted ions. Both proposed architectures can compete with state-of-the-art techniques opening the way to new ways of engineering multi-qubit gates in trapped ions using optical tweezers.

[1] M. Mazzanti, R. Gerritsma, R. J. C. Spreeuw and A. Safavi-Naini. arXiv:2301.04668 (2023)

[2] J.D. Espinoza, M. Mazzanti, K. Fouka, R.X. Schüssler, Z. Wu, P.Corboz Phys. Rev. A 104, 013302 (2021).

[3] M. Mazzanti, R.X. Schüssler, J.D. Espinoza,  Z. Wu, R. Gerritsma, A. Safavi-Naini  Phys. Rev. Lett. 127, 260502 (2021).