Unitary Operators and Quantum Dynamics

  • Lev I. Deych

In the previous section, I explained how one can dig out experimentally relevant information using states of a quantum system and operators representing the observables. The remaining burning question, however, is how can we find these states so that we could use these methods. In a typical experiment, an experimentalist begins by “preparing” a quantum system in some state, which they believe they know.1After that they smash the system with a hammer, or hit it by a laser light, or subject it to an electric or magnetic field, wait for some time, and measure new values of the selected observables. In order to predict the results of new measurements, you must be able to describe how the quantum system changes between the time of preparation and the time of subsequent measurement, or, speaking more scientifically, you must know its dynamics. As it has been made clear in the previous section, you need two objects to predict the results of a measurement: a state of the system and the...

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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Lev I. Deych
    • 1
  1. 1.Physics Department, Queens College and the Graduate CenterCity University of New YorkNew YorkUSA

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