Extended Data Fig. 3: Free-space optics schematic of the demonstration system.

Much of the complexity in the optical system is to match the receiver and transmitter FPAs, which can be corrected in the future by adjusting the chip layouts. For inexpensive consumer versions of the system, the Faraday rotator and polarizing beamsplitter could be replaced by a 50–50 beamsplitter, at the cost of a fourfold reduction in signal strength. Although it is possible to implement this experiment using a single chip for both transmit and receive functions, we have used two identical chips acting as the transmitter and receiver, respectively, to simplify the experimental set-up.