Measuring CP violation using quantum state tomography

TL;DR

This paper presents a quantum tomography-based method to measure direct CP violation in neutral meson decays, providing a more comprehensive and often more sensitive analysis than traditional asymmetry approaches.

Contribution

It introduces a novel quantum state tomography technique to quantify CP violation in meson decays, encompassing various meson types and final states, and discusses related quantum properties.

Findings

Quantum tomography effectively measures CP violation in neutral meson decays.

The method often surpasses traditional asymmetry-based measurements in sensitivity.

Applicable to different meson systems and final state configurations.

Abstract

We investigate direct CP violation in neutral meson decays by reconstructing the associated density matrices and measuring their difference using the trace distance. Our results cover neutral kaon decays into two scalar triplets of isospin space, specifically the pions, and decays of $B$- and $D$- mesons into two scalar octets of SU(3) flavor space. We briefly discuss the quantum properties of these states, including entanglement, contextuality, and nonlocality. Additionally, we demonstrate a comparable approach for spin-1 final states by employing a density matrix describing states in the space of helicities. The significance of CP violation obtained through this method is consistently comparable, and often surpasses that obtained using only single, or combinations of, asymmetries.