Could we quantum compute with electrons on helium?

Phil Platzman and Mark Dykman have recently suggested (Science 284 (1999) 1 967) that electrons on the surface of liquid helium could form a set of int eracting quantum bits (qubits) and, in principle, act as the basis for a qu antum computer This paper evaluates their proposal and discusses the techni cal and experimental challenges in implementing such a system.