Boosting projective methods for quantum process and detector tomography

TL;DR

This paper presents two advanced methods for quantum process and detector tomography that significantly improve accuracy and efficiency, enabling better characterization of quantum systems with larger qubits.

Contribution

The authors develop an analytical projection method for quantum channels and extend it to detector tomography, achieving substantial improvements over existing techniques.

Findings

Three-order-of-magnitude improvement in quantum channel approximation

Superior efficiency in detector tomography compared to current methods

Effective for systems up to four and six qubits in simulations

Abstract

We introduce two methods for quantum process and detector tomography. In the quantum process tomography method, we develop an analytical procedure for projecting the linear inversion estimation of a quantum channel onto the set of completely positive trace-preserving matrices. By integrating this method with alternate projection techniques, we achieve a three-order-of-magnitude improvement in approximating the closest quantum channel to an arbitrary Hermitian matrix compared to existing methods without compromising computational efficiency. Our second method extends this approach to quantum detector tomography, demonstrating superior efficiency compared to current techniques. Through numerical simulations, we evaluate our protocols across channels of up to four qubits in quantum process tomography and systems of up to six qubits in quantum detector tomography, showcasing superior precision and efficiency.