Two-Qubit Gate Set Tomography with Fewer Circuits

TL;DR

This paper introduces a method to significantly reduce the number of circuits needed for two-qubit gate set tomography by identifying and discarding redundant experiments, maintaining high accuracy while lowering experimental costs.

Contribution

It presents a novel approach to optimize GST circuit design by exploiting circuit structure, reducing experimental complexity without sacrificing precision.

Findings

Reduced the number of circuits needed for two-qubit GST

Maintained Heisenberg-like scaling in accuracy

Validated approach through simulations and Fisher information analysis

Abstract

Gate set tomography (GST) is a self-consistent and highly accurate method for the tomographic reconstruction of a quantum information processor's quantum logic operations, including gates, state preparations, and measurements. However, GST's experimental cost grows exponentially with qubit number. For characterizing even just two qubits, a standard GST experiment may have tens of thousands of circuits, making it prohibitively expensive for platforms. We show that, because GST experiments are massively overcomplete, many circuits can be discarded. This dramatically reduces GST's experimental cost while still maintaining GST's Heisenberg-like scaling in accuracy. We show how to exploit the structure of GST circuits to determine which ones are superfluous. We confirm the efficacy of the resulting experiment designs both through numerical simulations and via the Fisher information for said designs. We also explore the impact of these techniques on the prospects of three-qubit GST.