Probabilistic storage and retrieval of qubit phase gates

Understand

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 $N \rightarrow 1$ 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 $N/(N+1)$.