title: A two-qubit photonic quantum processor and its application to solving systems of linear equations.
abstract: Large-scale quantum computers will require the ability to apply long sequences of entangling gates to many qubits. In a photonic architecture, where single-qubit gates can be performed easily and precisely, the application of consecutive two-qubit entangling gates has been a significant obstacle. Here, we demonstrate a two-qubit photonic quantum processor that implements two consecutive CNOT gates on the same pair of polarisation-encoded qubits. To demonstrate the flexibility of our system, we implement various instances of the quantum algorithm for solving of systems of linear equations.
authors.affiliation: 1] Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria [2].
authors.forename: Stefanie
authors.initials: S
authors.lastname: Barz
authors.affiliation: 1] Department of Chemistry and Chemical Biology, Harvard University, Cambridge MA 02138, United States [2] Centre for Engineered Quantum Systems and Centre for Quantum Computing and Communication Technology, School of Mathematics and Physics, The University of Queensland, Brisbane QLD 4072, Australia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Kassal
authors.affiliation: 1] Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria [2].
authors.forename: Martin
authors.initials: M
authors.lastname: Ringbauer
authors.affiliation: Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Yannick Ole
authors.initials: YO
authors.lastname: Lipp
authors.affiliation: Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Borivoje
authors.initials: B
authors.lastname: Dakić
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge MA 02138, United States.
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.affiliation: Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Philip
authors.initials: P
authors.lastname: Walther