Clocked quantum-dot cellular automata shift register

The quantum-dot cellular automata (QCA) computational paradigm provides a means to achieve ultimately low limits of power dissipation by replacing binary coding in currents and voltages with single-electron switching within arrays of quantum dots (“cells”). Clocked control over the cells allows the realization of power gain, memory and pipelining in QCA circuits. We present an experimental demonstration of a clocked QCA two-stage shift register (SR) and use it to mimic the operation of a multi-stage SR. Error-bit rates for binary switching operations in a metal tunnel junction device are experimentally investigated, and discussed for future molecular QCAs.