A reversible full adder using adiabatic superconductor logic

Abstract

Reversible logic circuits can perform logic operations in a thermodynamically reversible manner, or without energy dissipation. The reversible quantum-flux-parametron (RQFP) is a reversible logic gate using adiabatic superconductor logic. In the present study, we design and demonstrate a reversible full adder (RFA) using RQFP gates in order to demonstrate that RQFP gates can be used as building blocks to design reversible logic circuits. An analysis of the time evolution of the phase differences across the Josephson junctions in the RFA showed that its logic state can change quasi-statically during a logic operation. Calculation of the energy dissipation of the RFA showed that it decreases in proportion to the operating frequency. These numerical calculation results ensure that the RFA is thermodynamically and logically reversible. In addition, we experimentally demonstrated correct operation of the RFA for all input data combinations. These results reveal that logic circuits designed using RQFP gates can perform reversible computing, i.e., RQFP gates can be used as building blocks of reversible logic circuits.

Adiabatic Quantum-Flux-Parametron: A Tutorial Review

“…In a numerical simulation, we showed that the RQFP can perform logic operations in a thermodynamically reversible manner (i.e., reversible computing) in the quasi-static limit [44]. Furthermore, we have fabricated and demonstrated an RQFP gate [43] and RQFP-based reversible full adder [90]. These demonstrations indicate that the RQFP is a practical reversible logic gate and can be used as a building block for making reversible computers.…”

Magnetic skyrmions and domain walls for logical and neuromorphic computing

“…The development of engineering concepts working toward the realization of this principle in concrete electronic systems began in the late 1970s [71,72]. Such research has continued, albeit at a low level of intensity, to this day, yielding concrete examples of low-power digital design techniques utilizing reversible computing principles for both semiconducting [73][74][75][76] and superconducting [77] technology platforms. Estimates of the minimum energy dissipation per reversible logic operation in leading-edge Complementary metal-oxide semiconductor (CMOS) technologies extend down to the sub-attojoule (order ∼100 kT, with T ≈ 300 K) range [78].…”

“…Estimates of the minimum energy dissipation per reversible logic operation in leading-edge Complementary metal-oxide semiconductor (CMOS) technologies extend down to the sub-attojoule (order ∼100 kT, with T ≈ 300 K) range [78]. But simulations of reversible superconducting circuits suggest that dissipation levels even below kT (with T = 4 K) are possible [77]. Might it be possible to approach or even breach kT dissipation levels at room temperature by using skyrmion interactions to do logic?…”

Quantum Foundations of Classical Reversible Computing

“…The Reversible Quantum Flux Parametron (RQFP) logic family [71][72][73] is a logically reversible variant of the well-developed superconducting logic family AQFP (Adiabatic Quantum Flux Parametron), which has been being developed primarily at Yokohama National University in Japan. RQFP (and its not-necessarily-reversible generalization AQFP) rely on adiabatic transformation of the abstract potential energy surface (PES) that obtains within Josephson-junction-based superconducting circuits.…”