Light and protein works like an transistor. Not only memory, if you use it , it records 5000 lines per mm hologram recording medium or as a 3D recording medium with using big cubes also. Its a optical computer where Soviets used as radar identification computer. Rhodopsin is the fastest transistor in the world.
The advantage , you can grow bactery in a bottle , extract rhodopsin and mix with a polymer to set. After that if you record a photograph , it carries it for years but if you light it with blue light , it deletes it. 10000000 times recordable and deletable.