Quantum Measurement Operations with Nanomagnets and Squids

The low-energy behaviour of 2 coupled nanomagnets or 2 coupled SQUIDs, interacting with their environment, can be described by the model of a “Pair or Interacting Spins Coupled to an Environmental Sea” (PISCES). These physical systems can then be used for a measurement operation in which system, apparatus and environment are all treated quantum mechanically. We design a “Bell/Coleman-Hepp” measuring system, and show that in principle one may design a situation in which quantum interference between system and apparatus can upset the usual measurement operation.