Matched detectors as definers of force

Formally distinguishing theory from experiment permits a proof that the choice of equations of quantum mechanics by which to model the devices of an experiment is in part free: no two practitioners need choose alike. Multiple, conflicting models are the rule, not the exception, so that particles as elements of theory have a certain independence from the devices they are invoked to explain. By recognizing this independence of particles from devices, we use quantum mechanics to describe devices used for ‘particle detection.’ First classically and then quantum mechanically, we show how a device to detect particles balances an unknown force against an adjustable reference. By augmenting an on-off detector with a matched pair of auxiliary detectors, we make the dynamics of its balancing accessible to experiment, and report results of a simplified experiment. We offer a quantum model of the balancing that shows a trade-off, involving Planck’s constant, between waiting time and ambiguity. Visible in records of disagreements between the two auxiliary detectors is a previously overlooked “dimension” to force, applicable to whatever form of force one undertakes to conceive of in terms of the balance instrument.