Meany Thomas, Biggerstaff Devon N, Broome Matthew A, Fedrizzi Alessandro, Delanty Michael, Steel M J, Gilchrist Alexei, Marshall Graham D, White Andrew G, Withford Michael J
Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia.
Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia.
Sci Rep. 2016 Jun 10;6:25126. doi: 10.1038/srep25126.
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.
扩大线性光学量子计算规模将需要多光子门，这些多光子门要紧凑、相位稳定、展现出优异的量子干涉，并且通过辅助光子的探测来宣告成功。我们研究了满足这些要求的最优已知门方案的设计、制造和表征：在集成激光写入波导阵列中实现的基尔受控Z门。我们表明，与耦合器反射率的小偏差相比，器件性能对电路中的相位变化不太敏感，考虑到制造方法的公差值，这是预期的。模式保真度也被证明比过程保真度对反射率和相位误差更不敏感。我们最好的器件与理想的4×4酉电路的保真度为0.931±0.001，与理想计算基过程的过程保真度为0.680±0.005。
