Southwest Quantum Information and Technology

Demonstration of near-infrared light shift gate on optical qubits and investigation of laser noise impact on gate fidelity

Presenting Author: Nicole Greene, University of California Berkeley
Contributing Author(s): Elia Perego Hartmut Haeffner

The typical native entangling gate for trapped ion systems is the Mølmer Sørensen gate. Here we demonstrate a wavelength insensitive alternative, the light shift gate, on a pair of Ca 40 ions. Instead of driving red and blue tones, we construct a running lattice to impart a time varying state dependent force on the ion pair. This gate has many advantages such as a better interaction strength scaling with power (linear with power instead of electric field), wavelength insensitivity allowing us to work with IR light, which is more ideal for integrated optics applications, and because it is a σz⊗σz interaction, spin echo pulses commute with the gate eliminating σz errors from unwanted stark shifts or drifts in laser frequency. We are working with an optical qubit (729nm transition) and using 794nm light to drive the gate. Because we are driving the gate near a dipole transition and we specifically accumulate phase on the D state making for simpler gate dynamics. We study how it performs under various parameters such as speed, ion spacing, and motional heating. Additionally, we investigate how laser noise reduces fidelity. We attempt to quantify what range constitute "medium" noise which is too slow to be averaged out, but too fast relative to the gate time to act as a constant offset.

(Session 8 : Friday from 2:45 pm - 3:15 pm)