Robust Calibration of a Universal Single-Qubit Gate-Set via Robust Phase Estimation

TL;DR

This paper introduces a robust, resource-efficient phase estimation method for calibrating single-qubit gates, achieving optimal accuracy without entanglement or complex resources, crucial for quantum computer development.

Contribution

It develops a robust phase estimation technique that accurately estimates systematic errors in single-qubit gates with provable efficiency and robustness, avoiding complex resources like entanglement.

Findings

Achieves Heisenberg scaling in parameter estimation.

Operates efficiently within a single-qubit Hilbert space.

Provides a robust calibration method for quantum gates.

Abstract

An important step in building a quantum computer is calibrating experimentally implemented quantum gates to produce operations that are close to ideal unitaries. The calibration step involves estimating the systematic errors in gates and then using controls to correct the implementation. Quantum process tomography is a standard technique for estimating these errors, but is both time consuming, (when one only wants to learn a few key parameters), and is usually inaccurate without resources like perfect state preparation and measurement, which might not be available. With the goal of efficiently and accurately estimating specific errors using minimal resources, we develop a parameter estimation technique, which can gauge key systematic parameters (specifically, amplitude and off-resonance errors) in a universal single-qubit gate-set with provable robustness and efficiency. In particular, our estimates achieve the optimal efficiency, Heisenberg scaling, and do so without entanglement and entirely within a single-qubit Hilbert space. Our main theorem making this possible is a robust version of the phase estimation procedure of Higgins et al. [B. L. Higgins, New J. Phys. 11, 073023 (2009)].