Virgile Adam of the Katholieke Universiteit Leuven in Belgium [and collbaorators] describe the ultimate in holographic (three-dimensional) data storage: a chemically pure crystal composed solely of proteins that can be read and reversibly switched between at least two different states using nothing but light.
Embedded within the proper array of lasers (it would take at least two), such a crystal would represent something approaching the theoretical limit of data density in a storage medium: each bit would be represented by a single molecule
… at least one of these proteins, known as IrisFP, actually has the ability to store data in four different states, versus the two different states (on and off) encoded by a traditional bit. In other words, this protein could store data in base 4 instead of base 2.
Technology Review | A Step Closer to Perfect 3-D Data Storage
