Testing Bell’s inequality using the Aharonov-Casher effect

We propose the Aharonov-Casher (AC) effect for four entangled spin-$\frac{1}{2}$ particles carrying magnetic moments in the presence of impenetrable line charge. The four-particle state undergoes an AC phase shift in two causally disconnected regions, which can show up in the correlations between different spin states of distant particles. This correlation can violate Bell’s inequality, thus displaying the nonlocality for four-particle entangled states in an objective way.