Optically writable atomic vapor memory as a substrate for optical reservoir computing

We present an optical random access memory (ORAM) based on warm cesium (Cs) atomic vapor and demonstrate its operation as the physical substrate of a reservoir computer. Information is stored in the hyperfine population distribution of a Cs ensemble via optical pumping and retrieved through differential probe absorption. Spatial multiplexing via acousto-optic deflection provides eight addressable memory rails able to store up to 3.9 bits of information per rail. Employing this platform as a temporally multiplexed reservoir, we achieve a kernel rank (KR =8.8 ± 0.4), and a minimum bit error rate of 0.02 ± 0.01 on the Exclusive-or (XOR) benchmark. We find the limited memory lifetime constrains the achievable temporal depth, encouraging further research into fast addressable memories. This constitutes the first demonstration of a free-space, optically writable atomic RAM as a substrate in an optical reservoir computing system.