Further compactifying linear optical unitaries
Further compactifying linear optical unitaries
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DOI：
10.1063/5.0053421
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发表时间：
2021-07-01
期刊：
影响因子：
5.6
通讯作者：
Walmsley, I. A.
中科院分区：
文献类型：
--
作者：
Bell, B. A.;Walmsley, I. A.
量子集成光子学需要大规模线性光学电路，并且对于许多应用，期望具有通用可编程电路，能够在多个模式上实现任意的么正变换。这已经实现了使用Reck计划，包括一个网络的马赫-曾德尔干涉仪包含一个可变的移相器在一个路径，以及一个外部移相器后，每个马赫-曾德尔。随后变得明显的是，在对称马赫-曾德尔在两个路径中都包含移相器的情况下，外部移相器是冗余的，从而导致更紧凑的电路。矩形克莱门茨计划在电路深度方面改进了Reck计划，但人们认为在每个马赫-曾德尔之后需要一个外部移相器。在这里，我们表明，克莱门茨计划可以实现使用对称马赫-曾德尔，只需要少量的外部移相器，不有助于电路的深度。这将显著节省这些器件的长度，允许更复杂的电路安装到光子芯片上，并减少与这些电路相关的传播损耗。我们还讨论了如何类似的储蓄可以替代方案，具有鲁棒性不平衡分束器。
Quantum integrated photonics requires large-scale linear optical circuitry, and for many applications, it is desirable to have a universally programmable circuit, able to implement an arbitrary unitary transformation on a number of modes. This has been achieved using the Reck scheme, consisting of a network of Mach-Zehnder interferometers containing a variable phase shifter in one path as well as an external phase shifter after each Mach-Zehnder. It subsequently became apparent that with symmetric Mach-Zehnders containing a phase shifter in both paths, the external phase shifters are redundant, resulting in a more compact circuit. The rectangular Clements scheme improves on the Reck scheme in terms of circuit depth, but it has been thought that an external phase-shifter was necessary after each Mach-Zehnder. Here, we show that the Clements scheme can be realized using symmetric Mach-Zehnders, requiring only a small number of external phase-shifters that do not contribute to the depth of the circuit. This will result in a significant saving in the length of these devices, allowing more complex circuits to fit onto a photonic chip, and reducing the propagation losses associated with these circuits. We also discuss how similar savings can be made to alternative schemes, which have robustness to imbalanced beam-splitters.