Localisation of pair charge states in a superconducting weak link constriction ring

Abstract We show that for sufficiently small values of weak link capacitance in a superconducting weak link constriction (SQUID) ring it becomes possible to observe the localisation of pair (2 e ) charge on the weak link. This has allowed us to construct a quantum mechanical Faraday law voltmeter conjugate to the well-known radio frequency biased SQUID magnetometer.