Fig. 2
From: Implementation of double Feynman gate in high dimensional quantum systems
Experimental setup for the double Feynman gate. A 405 nm diode laser pumps a type-II PPKTP crystal to generate orthogonally polarized, correlated photon pairs. The vertically polarized idler photon is used to herald the horizontally polarized signal photon. SLM1, mirror and a set of plates are employed to modulate the transverse and polarization modes of the signal photon independently. Blocks (a)–(c) are designed to implement the interchange operation of the double Feynman gate in the OAM-encoded Hilbert space. Finally, the two photon paths are recombined at the PBS2, and the photon is projectively detected via SLM2 and SMF. (The digital drawings in this figure were created by Yanbing Zhu using SOLIDWORKS® Premium 2019 SP0.0, while device annotations were added with Microsoft Visio® 2021. For further details, refer to the official websites of SOLIDWORKS® 2019 (https://www.solidworks.com/) and Microsoft Visio® 2021 (https://www.microsoft.com/en-us/microsoft-365/visio/).)
