Concerning the state-change due to the measurement process


  • Reprint of ‘Über die Zustandsänderung durch den Meßprozeß’ by G. Lüders, Ann. Phys. (Leipzig) 8, 322–328 (1951), available on-line at Translation and discussion by K. A. Kirkpatrick, New Mexico Highlands University, Las Vegas, New Mexico 87701, USA

  • (Received at editorial Office on 18 October 1950.)


The statistical transformation theory contains procedures for the computation of measurement probabilities, but requires for its completion a statement about the state-change due to the measurement process. We discuss and reject an ansatz suggested for this by J. von Neumann. We submit an ansatz for the state-change which is essentially identical to the ‘reduction of the wave function’. It permits a deepening of the concept of compatibility of measurements. Finally, measurements of states subject to con straints are considered.