REPEATABLE MEASUREMENTS IN QUANTUM-THEORY - THEIR ROLE AND FEASIBILITY

Recent advantages in experimental quantum physics call for a careful r econsideration of the measurement process ill quantum mechanics. III t his paper we describe the structure of the ideal measurements and thei r status among tile repeatable measurements. Then we provide an exhaus tive account of tile interrelations between repeatability and the appa rently weaker notions of value reproducible oi first-kind measurements . We demonstrate the close link between repeatable measurements and di screte observables and show how the ensuing measurement limitations fo r continuous observables can be lifted in a way that is ill full accor dance with actual experimental practice. We present examples of almost repeatable measurements of continuous observables and some realistic models of weakly disturbing measurements.