  We investigate quantum state reconstruction of a superconducting qubit
threaded by an Aharonov-Bohm flux, with particular attention to the local
geometric phase. A state reconstruction scheme is introduced with a proper
account of the local geometric phase generated by Faraday's law of induction.
Our scheme is based on measurement of three complementary quantities, that is,
the extra charge and two local currents. Incorporating time-reversal symmetry
and the Faraday's law, we show that the full density matrix can be
reconstructed without ambiguity in the choice of gauge. This procedure clearly
demonstrates that the quantum Faraday effect plays an essential role in the
dynamics of a quantum system that involves Aharonov-Bohm flux.
