Impact of parity violation on quantum entanglement and Bell nonlocality

TL;DR

This paper explores how parity violation affects quantum entanglement and Bell nonlocality in particle decays, revealing that P violation can fully disentangle pairs and impact Bell test validity, with environmental magnetic fields further complicating measurements.

Contribution

It provides a detailed analysis of parity violation's impact on QE and Bell nonlocality in spin systems, highlighting conditions for disentanglement and proposing testing methods, while emphasizing environmental effects.

Findings

Parity violation can cause complete disentanglement of particle pairs.

Bell tests may become ineffective under maximal P violation.

Magnetic fields in detectors induce spurious P and CP violations.

Abstract

Quantum entanglement (QE), evidenced by Bell inequality (BI) violations, reveals the nonlocality of nature. Fundamental interactions manifest in various forms, each with distinct effects on QE and BI, but have not yet been studied in depth. We investigate in detail the relationship between QE, Bell nonlocality, and parity-violating interactions in spin-1/2 bipartite systems arising from the decays of spin-0 and spin-1 particles within the quantum field theory (QFT). Our findings reveal that parity (P) violation can completely disentangle particle pairs, rendering Bell tests ineffective in distinguishing between classical and quantum theories. In the spin-0 case, complete disentanglement occurs at maximal P violation, which is similarly true for spin-1 decays. Without restrictions from the QFT, the predicted relation between entanglement and the Bell nonlocality may no longer be valid and we propose promising methods for testing it. Additionally, we emphasize the previously overlooked influence of magnetic fields within detectors, which alters predictions for QE and Bell nonlocality. This environmental effect induces spurious P and charge-parity (CP) violations and thus has to be subtracted for genuine P, CP, and Bell tests.