Experimental replication of single-qubit quantum phase gates
Michal Mičuda, Robert Stárek, Ivo Straka, Martina Miková, Michal Sedlák, Miroslav Ježek, Jaromı́r Fiurášek · Physical Review A · 2016
We experimentally demonstrate the underlying physical mechanism of the recently proposed protocol for superreplication of quantum phase gates [W. D\"ur, P. Sekatski, and M. Skotiniotis, Phys. Rev. Lett. 114, 120503 (2015)], which allows producing up to ${N}^{2}$ high-fidelity replicas from $N$ input copies in the limit of large $N$. Our implementation of $1\ensuremath{\rightarrow}2$ replication of the single-qubit phase gates is based on linear optics and qubits encoded into states of single photons. We employ the quantum Toffoli gate to imprint information about the structure of an input two-qubit state onto an auxiliary qubit, apply the replicated operation to the auxiliary qubit, and then disentangle the auxiliary qubit from the other qubits by a suitable quantum measurement. We characterize the replication protocol by full quantum process tomography and observe good agreement of the experimental results with theory.