Bistable locking of single-electron tunneling elements for digital circuitry

Bistable phase locking of single-electron tunneling oscillations is proposed as the basis for digital logic circuitry. A simple model of single-electron tunneling is used to examine the locking of capacitively coupled junctions pumped at twice the tunneling frequency and activated by clocking the dc bias. The locking to sinusoidal input signals and the locking between coupled junctions is examined. It is shown that bistable locking exhibits an input amplitude threshold and phase noise margin and that junctions rapidly lock in antiphase due to a strong interaction between tunneling events. Conditions under which the operation is potentially useful for digital circuitry are identified.