Certain flavors of superconducting digital logic (there are a handful) such as AQFP (adiabatic quantum flux parametron) actually get close to the Landauer limit

Certain flavors of superconducting digital logic (there are a handful) such as AQFP (adiabatic quantum flux parametron) actually get close to the Landauer limit (with cooling power excepted). Interconnect (as some comments have noted) and lack of a good memory technology are the challenges for all these architectures.