Efficient tomography of quantum processes

TL;DR

This paper introduces a highly efficient quantum process tomography method that uses minimal test states, significantly reducing the resources needed for identifying quantum processes, especially in multi-mode systems.

Contribution

It provides explicit formulas for complete quantum process identification using only one weakly entangled state or a few coherent states, improving efficiency over existing methods.

Findings

Complete quantum process identification with one weakly entangled state

Efficient tomography of Gaussian processes with minimal states

Exponential reduction in test states for multi-mode processes

Abstract

We show with explicit formulas that one can completely identify an unknown quantum process with only one weakly entangled state; and identify a quantum optical Gaussian process with either one two-mode squeezed state or a few different coherent states. In tomography of a multi-mode process, our method reduces the number of different test states exponentially compared with existing methods.