Abstract

The ability of the scanning tunnelling microscope to manipulate single atoms and molecules has allowed a single bit of information to be represented by a single atom or molecule. Although such information densities remain far beyond the reach of real-world devices, it has been assumed that the finite spacing between atoms in condensed-matter systems sets a rigid upper limit on information density. Here, we show that it is possible to exceed this limit with a holographic method that is based on electron wavefunctions rather than free-space optical waves. Scanning tunnelling microscopy and holograms comprised of individually manipulated molecules are used to create and detect electronically projected objects with features as small as |[sim]|0.3|[nbsp]|nm, and to achieve information densities in excess of 20|[nbsp]|bits|[nbsp]|nm|[minus]|2. Our electronic quantum encoding scheme involves placing tens of bits of information into a single fermionic state.