Extracting the physical sector of quantum states

TL;DR

This paper presents a method to systematically extract the finite-dimensional physical sector of quantum states using only measurement data, enhancing state tomography for quantum sources.

Contribution

It introduces a data-driven procedure for extracting the physical sector of quantum states without assumptions, applicable to various quantum systems.

Findings

Effective extraction demonstrated on simulated quantum light sources

Method works with experimental quantum data

Applicable to finite-dimensional quantum systems

Abstract

The physical nature of any quantum source guarantees the existence of an effective Hilbert space of finite dimension, the physical sector, in which its state is completely characterized with arbitrarily high accuracy. The extraction of this sector is essential for state tomography. We show that the physical sector of a state, defined in some pre-chosen basis, can be systematically retrieved with a procedure using only data collected from a set of commuting quantum measurement outcomes, with no other assumptions about the source. We demonstrate the versatility and efficiency of the physical-sector extraction by applying it to simulated and experimental data for quantum light sources, as well as quantum systems of finite dimensions.