ИСТИНА

Experimental implementation of a quantum computing algorithm strongly relies on the ability to construct required unitary transformations applied to the input quantum states. In particular, near-term linear optical computing requires universal programmable interferometers, capable of implementing an arbitrary transformation of input optical modes. So far, these devices were composed as a circuit with well-defined building blocks, such as balanced beamsplitters. This approach is vulnerable to manufacturing imperfections inevitable in any realistic experimental implementation, and the larger the circuit size grows, the stricter the tolerances become. In this work we demonstrate a new methodology for the design of the high-dimensional mode transformations, which overcomes this problem, and carefully investigate its features. The circuit in our architecture is composed of interchanging mode mixing layers, which may be almost arbitrary, and layers of variable phaseshifters, allowing to program the device to approximate any desired unitary transformation.