New Aspects of Geometric Phases in Experiments with polarized Neutrons

TL;DR

This paper explores geometric phases in polarized neutron experiments, demonstrating their effects in various setups, including polarimeters and interferometers, and analyzing their influence on quantum entanglement and Bell inequalities.

Contribution

It provides new experimental evidence of geometric phases in neutron systems and investigates their impact on quantum measurements and entanglement.

Findings

Observation of non-additivity of quantum phases for mixed states

Verification of geometric phases induced by oscillating magnetic fields

Demonstration that geometric phases can be balanced by adjusting Bell angles

Abstract

Geometric phase phenomena in single neutrons have been observed in polarimeter and interferometer experiments. Interacting with static and time dependent magnetic fields, the state vectors acquire a geometric phase tied to the evolution within spin subspace. In a polarimeter experiment the non-additivity of quantum phases for mixed spin input states is observed. In a Si perfect-crystal interferometer experiment appearance of geometric phases, induced by interaction with an oscillating magnetic field, is verified. The total system is characterized by an entangled state, consisting of neutron and radiation fields, governed by a Jaynes-Cummings Hamiltonian. In addition, the influence of the geometric phase on a Bell measurement, expressed by the Clauser-Horne-Shimony-Holt (CHSH) inequality, is studied. It is demonstrated that the effect of geometric phase can be balanced by an appropriate change of Bell angles.