  In most experiments on flux qubits,the "measurement" is performed by coupling
the system to a dc SQUID and recording the distribution of switching currents
for the latter;this measurement protocol is very far from the classic von
Neumann ("projective") scheme,in that very little information is obtained from
a single run,rather one has to repeat the experiment tens of thosands of times
to extract anything useful.Here, concentrating on the equlibrium behavior of
the flux qubit,we carry out an analytic calculation of the dc-SQUID switching
current distribution as a function of external bias flux on the qubit,and
compare our predictions with the data from experiments conducted at Delft and
NTT.
