CAN UNSHARP OBJECTIFICATION SOLVE THE QUANTUM MEASUREMENT PROBLEM

The quantum measurement problem is formulated in the form of an insolu bility theorem that states the impossibility of obtaining, for all ava ilable object preparations, a mixture of states of the compound object and apparatus system that would represent definite pointer positions. A proof is given that comprises arbitrary object observables, whether sharp or unsharp, and besides sharp pointer observables a certain cla ss of unsharp pointers, namely, those allowing for the property of poi nter value definiteness. A recent result of H. Stein is applied to all ow for the possibility that a given measurement may not be applicable to all possible object states, but only to a subset of them. The quest ion is raised whether the statement of the insolubility theorem remain s true for genuinely unsharp observables. This gives rise to a precise notion of unsharp objectification.