“Second, this proof-of-concept work focused on binary computing functions with a cube being either pushed up or pushed down – it’s either a 1 or a 0. But we think there is potential here for more complex computing, with data being conveyed by how high a given cube has been pushed up. We’ve shown within this proof-of-concept system that cubes can have five or more different states. Theoretically, that means a given cube can convey not only a 1 or a 0, but also a 2, 3 or 4.”
Is this trying to straddle the line between analog and digital computing? Because it sounds like they are describing a crippled analog computer system.
Digital doesn't mean binary. A digital system must simply occupy a fixed number of levels, rather than the contiguous values of an analogue system. Binary systems, with 1 and 0, just happen to be one example of that.
There's plenty of non-binary schemes used in modern digital systems though. Modern NAND flash is one instance, for example QLC SSD drives store 16 distinct levels per storage cell (allowing each to encode the equivalent of 4-bits of data). Another example is 64-QAM, a modulation scheme used in a variety of places, including 802.11n Wi-Fi and Digital Terrestrial television (among others), which forms symbols out of two out of phase sinusoids, each of which can take up to 8 amplitude levels.
And even electronic computers haven't always been binary, one of the early Soviet computers was ternary, relying on 3 digits rather than the more familiar 2, to do all of its core computing functions.
Some existing digital storage uses multiple levels beyond 0 and 1 for improved density. For instance, the 8087 floating-point coprocessor used a ROM with four levels to store its microcode with two bits per transistor, as a regular ROM was too big for the die. Flash memory uses multi-level cells with up to 4 bits per cell.
Is this trying to straddle the line between analog and digital computing? Because it sounds like they are describing a crippled analog computer system.