Probabilistic storage and retrieval of qubit phase gates

Abstract

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 [PRL 122, 170502 (2019)]. Here we study improvements due to a priori knowledge about the unitary transformation to be stored. In particular, we study $N\to 1$ PSR of qubit phase gates, i.e. qubit rotations a round $Z$ 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 programmable phase gate [PRL 88, 047905 (2002)] can be turned into $(2^k-1)\to 1$ optimal PSR of phase gates and requires only $k$ CNOT gates, while having exponentially small failure probability in $k$.

9 pages, 7 figures

References in corpus (5)

• Quantum Circuits Architecture
• Transforming quantum operations: quantum supermaps
• Asymptotic teleportation scheme as a universal programmable quantum processor
• Quantum teleportation scheme by selecting one of multiple output ports
• Optimality of programmable quantum measurements

Cited by in corpus (1)

• Robustness of optimal probabilistic storage and retrieval of unitary channels to noise