A Quantum Logic Gate Representation of Quantum Measurement: Reversing and Unifying the Two Steps of von Neumann's Model

摘要

In former work, quantum computation has been shown to be a problem solvingprocess essentially affected by both the reversible dynamics leading to thestate before measurement, and the logical-mathematical constraints introducedby quantum measurement (in particular, the constraint that there is only onemeasurement outcome). This dual influence, originated by independent initialand final conditions, justifies the quantum computation speed-up and is notrepresentable inside dynamics, namely as a one-way propagation. In this work,we reformulate von Neumann's model of quantum measurement at the light of abovefindings. We embed it in a broader representation based on the quantum logicgate formalism and capable of describing the interplay between dynamical andnon-dynamical constraints. The two steps of the original model, namely (1)dynamically reaching a complete entanglement between pointer and quantum objectand (2) enforcing the one-outcome-constraint, are unified and reversed. Byrepresenting step (2) right from the start, the same dynamics of step (1)yields a probability distribution of mutually exclusive measurement outcomes.This appears to be a more accurate and complete representation of quantummeasurement. PACS: 03.67.-a, 03.67.Lx, 03.65.Bz