As covered in the article [1, paywalled], the binary cell itself consists of two flipflops, each at 6x2 mm², and an optical xor (no dimensions given). So for th

As covered in the article [1, paywalled], the binary cell itself consists of two flipflops, each at 6x2 mm², and an optical xor (no dimensions given). So for the time being, most of the space is in the control logic, as would be expected for a first proof of concept. Currently, the answer to your question seems "not very", but if the tech proves to be viable it will certainly attract a lot of further research & funding to minimize it. Compare first proof of concept memory cells vs what followed in the years to come. [1] https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-7-1821 https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-7-18...