Universal Linear Optics

• Main Authors: Carolan, Jacques, Harrold, Chris, Sparrow, Chris, Martín-López, Enrique, Russell, Nicholas J, Silverstone, Joshua W, Shadbolt, Peter J, Matsuda, Nobuyuki, Oguma, Manabu, Itoh, Mikitaka, Marshall, Graham D, Thompson, Mark G, Matthews, Jonathan C. F, Hashimoto, Toshikazu, O'Brien, Jeremy L, Laing, Anthony
• Format: Journal Article
• Language: English
• Published: 05-05-2015
• Subjects: Physics - Quantum Physics
• DOI: 10.48550/arxiv.1505.01182

Science 349, 711 (2015) Linear optics underpins tests of fundamental quantum mechanics and computer
science, as well as quantum technologies. Here we experimentally demonstrate
the longstanding goal of 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 average fidelity 0.999 $\pm$ 0.001. Our system is
capable of switching between these and any other linear optical protocol in
seconds. These results point the way to applications across fundamental science
and quantum technologies.