The Free On-line Dictionary of Computing (30 December 2018):

Quantum-dot Cellular Automata
QCA

    (QCA) Quantum logic circuits created
   by orientating pairs of quantum cells so that their relative
   positions determine their affect on each other.  This is
   functionally analogous but structurally different from how
   individual gates in integrated circuits are combined to
   create logical and memory circuitry.

   The advantages of quantum-dot cellular automata over
   conventional circuitry are extremely small size/high density,
   low power requirements, and potentially high processing
   speeds.  Disadvantages (in 2000) are difficulty of fabrication
   and low yield.

   See also: quantum cell wire.

   (http://nd.edu/~qcahome/).

   (http://mitre.org/research/nanotech/quantum_dot_cell.html).

   ["Quantum Dot Heterostructures", D. Bimberg, et al, John Wiley
   & Sons Ltd., Dec 1998].

   (2001-07-17)