title: QUANTUM OPTICS. Universal linear optics.
abstract: Linear optics underpins fundamental tests of quantum mechanics and quantum technologies. We demonstrate a single reprogrammable optical circuit that is sufficient to implement all possible linear optical protocols up to the size of that circuit. Our six-mode universal system consists of a cascade of 15 Mach-Zehnder interferometers with 30 thermo-optic phase shifters integrated into a single photonic chip that is electrically and optically interfaced for arbitrary setting of all phase shifters, input of up to six photons, and their measurement with a 12-single-photon detector system. We programmed this system to implement heralded quantum logic and entangling gates, boson sampling with verification tests, and six-dimensional complex Hadamards. We implemented 100 Haar random unitaries with an average fidelity of 0.999 ± 0.001. Our system can be rapidly reprogrammed to implement these and any other linear optical protocol, pointing the way to applications across fundamental science and quantum technologies.
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Jacques
authors.initials: J
authors.lastname: Carolan
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Harrold
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK. Department of Physics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Sparrow
authors.affiliation: Nokia Technologies, Broers Building, 21 J. J. Thomson Avenue, Cambridge CB3 0FA, UK.
authors.forename: Enrique
authors.initials: E
authors.lastname: Martín-López
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Russell
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Silverstone
authors.affiliation: Department of Physics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Shadbolt
authors.affiliation: NTT Basic Research Laboratories, Nippon Telegraph and Telephone (NTT) Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Matsuda
authors.affiliation: NTT Device Technology Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Oguma
authors.affiliation: NTT Device Technology Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Mikitaka
authors.initials: M
authors.lastname: Itoh
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Marshall
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Thompson
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Jonathan C F
authors.initials: JC
authors.lastname: Matthews
authors.affiliation: NTT Device Technology Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: O'Brien
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory, and Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK. anthony.laing@bristol.ac.uk.
authors.forename: Anthony
authors.initials: A
authors.lastname: Laing