Engineering integrated photonics for heralded quantum gates.
Scaling up linear-optics quantum computing will require multi-photon gates which are compact, phase-stable, exhibit excellent quantum interference, and have success heralded by the detection of ancillary photons. We investigate the design, fabrication and characterisation of the optimal known gate scheme which meets these requirements: the Knill controlled-Z gate, implemented in integrated laser-written waveguide arrays. We show device performance to be less sensitive to phase variations in the circuit than to small deviations in the coupler reflectivity, which are expected given the tolerance values of the fabrication method. The mode fidelity is also shown to be less sensitive to reflectivity and phase errors than the process fidelity. Our best device achieves a fidelity of 0.931 ± 0.001 with the ideal 4 × 4 unitary circuit and a process fidelity of 0.680 ± 0.005 with the ideal computational-basis process.
Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
Thomas
T
Meany
Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.|Centre for Quantum Computer and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.
Devon N
DN
Biggerstaff
Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.|Centre for Quantum Computer and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.
Matthew A
MA
Broome
Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.|Centre for Quantum Computer and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.|Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Alessandro
A
Fedrizzi
Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
Michael
M
Delanty
Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
M J
MJ
Steel
Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
Alexei
A
Gilchrist
Centre for Quantum Photonics, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK.
Graham D
GD
Marshall
Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.|Centre for Quantum Computer and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.
Andrew G
AG
White
Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
Michael J
MJ
Withford