  A change of quantum states for a quantum particle may lead to a change of
physical field it exerts to the environment. We discuss such Gedankenexperiment
for measuring the magnetic dipole fields associated with the electronic spins.
When entangled, electrons are no longer free Dirac electrons but become an
excited state in a quantum-electrodynamics sense. A measurement of magnetism
associated with entanglement-collapse of electrons becomes a test for
Copenhagen interpretation in the reign of quantum-electrodynamics. This
proposal is equally applicable to other particles and their associated fields
and interactions, such as neutrons and the electroweak force.
