title: Adding control to arbitrary unknown quantum operations.
abstract: Although quantum computers promise significant advantages, the complexity of quantum algorithms remains a major technological obstacle. We have developed and demonstrated an architecture-independent technique that simplifies adding control qubits to arbitrary quantum operations-a requirement in many quantum algorithms, simulations and metrology. The technique, which is independent of how the operation is done, does not require knowledge of what the operation is, and largely separates the problems of how to implement a quantum operation in the laboratory and how to add a control. Here, we demonstrate an entanglement-based version in a photonic system, realizing a range of different two-qubit gates with high fidelity.
authors.affiliation: Centre for Quantum Photonics, H.H. Wills Physics Laboratory & Department of Electrical and Electronic Engineering, University of Bristol, UK.
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Zhou
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Ralph
authors.forename: Pruet
authors.initials: P
authors.lastname: Kalasuwan
authors.forename: Mian
authors.initials: M
authors.lastname: Zhang
authors.forename: Alberto
authors.initials: A
authors.lastname: Peruzzo
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Lanyon
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: O'Brien