Abstract
Recently, Gudder proved that the set of all generalized quantum gates coincides the set of all contractions in a finite-dimensional Hilbert space (S. Gudder, Int. J. Theor. Phys. 47:268–279, 2008). In this note, we proved that the set of all generalized quantum gates is a proper subset of the set of all contractions on an infinite dimensional separable Hilbert space ℋ. Meanwhile, we proved that the quantum operation deduced by an isometry is an extreme point of the set of all quantum operations on ℋ.
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This subject is supported by NSF of China (10571113).
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Wang, YQ., Du, HK. & Dou, YN. Note on Generalized Quantum Gates and Quantum Operations. Int J Theor Phys 47, 2268–2278 (2008). https://doi.org/10.1007/s10773-008-9659-4
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DOI: https://doi.org/10.1007/s10773-008-9659-4