High-fidelity quantum gates via optimizing short pulse sequences in three-level systems

Abstract

We propose a robust and high-fidelity scheme for realizing universal quantum gates by optimizing short pulse sequences in a three-level system. To alleviate the sensitivity to the errors, we recombine all elements of error matrices to construct a cost function with three types of weight factors. The modulation parameters are obtained by searching for the minimum value of this cost function. The purposes of introducing the weight factors are to reduce the detrimental impact of high-order error matrices, suppress population leakage to the third state, correct the operational error in the qubit space, and optimize the total pulse area of short pulse sequences. The results demonstrate that the optimized sequences exhibit strong robustness against errors and effectively reduce the total pulse area. Therefore, this work presents a valuable method for achieving exceptional robustness and high speed in quantum computations.

Optimal narrowband composite pulses in two-level systems

“…(iii) Search for the minimum value of the cost function. To this end, we employ the Lagrange multiplier method [51,52], because this method is very suitable for solving constrained optimization problems. The main idea of the Lagrange multiplier method is to transform an optimization problem with specific constraints into an unconstrained one by introducing new parameters (i.e., Lagrange multipliers).…”