Can a noninvasive measurement of magnetic flux be performed with superconducting circuits?

A gedanken experiment is described in which the noninvasive determination of joint probability densities for the magnetic flux linking a superconducting quantum-interference device is determined using variable threshold superconducting switches followed by superconducting magnetometers. As a result, it is demonstrated that an important prediction of quantum mechanics can be tested in principle against those of macrorealistic theories using superconducting circuits. © 1990 The American Physical Society.