Phase transitions in sequential weak measurements
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AbstractQuantum measurement can be strong or weak, the former being important in readout and initialization of quantum objects and the latter being useful for monitoring and maneuvering quantum evolution. However, the boundary between weak and strong measurement is unclear. Here we show that a phase transition occurs in sequential quantum measurement, which unambiguously separates the weak and strong measurement by a critical value of measurement strength or duration. We formulate the probability distribution of the output of a sequence of quantum measurements as the Boltzmann distribution of an interacting spin model. The measurement results present phase transitions similar to those in the spin model. In particular the sequential commuting positive operator-valued measurement is mapped to a long-range Ising model, and a projective measurement emerges from sequential weak measurements when the strength or the number of measurements becomes above certain critical values, corresponding to the ferromagnetic phase transition of the spin model. This finding sheds insights on sequential quantum measurement, and also provides the theoretical foundation for constructing projective measurements from sequential weak measurements, which have applications in steering the quantum evolution and initializing quantum systems where strong measurement in a single shot is often not possible.
All Author(s) ListMa WL, Wang P, Leong WH, Liu RB
Journal namePhysical Review A
Volume Number98
Issue Number1
Article number012117
LanguagesEnglish-United Kingdom
Web of Science Subject CategoriesOptics;Physics, Atomic, Molecular & Chemical;Optics;Physics

Last updated on 2021-06-05 at 01:53