Probabilistic storage and retrieval of qubit phase gates

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Authors

SEDLÁK Michal ZIMAN Mário

Year of publication 2020
Type Article in Periodical
Magazine / Source Physical Review A
MU Faculty or unit

Faculty of Informatics

Citation
Web https://doi.org/10.1103/PhysRevA.102.032618
Doi http://dx.doi.org/10.1103/PhysRevA.102.032618
Keywords quantum technologies; quantum information
Attached files
Description Probabilistic storage and retrieval (PSR) of unitary quantum dynamics is possible with exponentially small failure probability with respect to the number of systems used as a quantum memory [M. Sedlák, A. Bisio, and M. Ziman, Phys. Rev. Lett. 122, 170502 (2019)]. Here we study improvements due to a priori knowledge about the unitary transformation to be stored. In particular, we study N-->1 PSR of qubit phase gates, i.e., qubit rotations around the Z axis with an unknown angle, and show that if we access the gate only N times the optimal probability of perfect retrieving of its single use is N/(N+1). We propose a quantum circuit realization for the optimal protocol and show that a programmable phase gate [G. Vidal, L. Masanes, and J. I. Cirac, Phys. Rev. Lett. 88, 047905 (2002)] can be turned into a (2k-1)-->1 optimal PSR of phase gates and requires only k controlled-not gates, while having exponentially small failure probability in k.
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