Design and operation of a Quantum Flux Parametron bit-slice ALU

The design of Quantum Flux Parametron (QFP) majority logic circuits presents a number of unique constraints. For example, interconnects must be kept short and have a common small inductance. The former suggests that the bit-slice architecture is well suited to QFP circuits. In order to test this conjecture, a suitably complex logic circuit was designed and a small part of it was fabricated. A design for a 16-function bit-slice arithmetic-logic unit (ALU) was found that satisfied the constraints. It can compute on n-bit operands in 2n+4 QFP stages. A reduced version of the bit-slice ALU cell, containing 30 QFP´s, was fabricated and successfully tested at low speed. The design experience showed that complex combinatorial QFP logic circuits are possible. Larger circuits will be feasible with computer-aided tools.<>