Phase-controlled two-qubit quantum gates

Abstract

We consider an implementation of a two-qubit entangling gate between trapped ions controlled by fully overlapping laser pulses. We particularly address the role of a relative phase between the pulses in the gate design. Though, in general, the relative phase determines the exact form of the two-qubit operation, it is shown that it affects only its single qubit part and has no effect on its entangling content. Based on a general canonical decomposition of the evolution operator we demonstrate that the controlled-not (cnot) gate can be decomposed in terms of a two-qubit entangled gate and single qubit phase gates. Our study shows that any relative phase errors in two-qubit operations related to phase fluctuations of the external fields can be successfully corrected locally by single-qubit operations, which are usually easy to implement.