  New method to probe quantum dynamics of the order parameter phase of a small
superconductive island is proposed. The idea is to measure Andreev subgap
conductance between the island and a dirty normal-metal wire connected with the
island by very high-resistance tunnel barrier. The phase on the island is
supposed to stay primarly in one of the two nearly degenerate classical minima
i.e. the island is an active element of the Superconductive Phase Qubit.
Voltage-dependence of the differential subgap conductance measured at low
temperatures are predicted to demonstrate crucially different behavior
depending on the type of the internal dynamics of phase (coherent tunnelling of
phase, non-coherent tunnelling, or no tunneling). Thus the measurements of
nonliner Andreev conductance is a tool to probe the type of quantum behavior of
the artificial two-level system.
