Two-qubit quantum gates with minimal pulse sequences

Abstract

Working with trapped atoms at close distance to each other, we show that one can implement entangling gates based on non-independent qubits using a single pulse per qubit, or a single structured pulse. The optimal parameters depend on approximate solutions of Diophantine equations, causing the fidelity to never be exactly perfect, even under ideal conditions, although the errors can be made arbitrarily smaller at the cost of stronger fields. We fully characterize the mechanism by which the gates operate, and show that the main source of error in realistic implementations comes from fluctuations in the peak intensity, which especially damages the fidelity of the gates that use stronger fields. Working with two-pulse sequences, instead of one, enables the use of a plethora of mechanisms and a broad range of optimal parameters to choose from, to achieve high-fidelity gates.