Implementation of energy efficient single flux quantum digital circuits with sub-aJ bit operation

We report the first experimental demonstration of recently proposed energy efficient single flux quantum logic, eSFQ. This logic can represent the next generation of RSFQ logic, eliminating the dominant static power dissipation associated with a dc bias current distribution and providing over two orders of magnitude efficiency improvement over conventional RSFQ logic. We further demonstrate that the introduction of passive phase shifters allows the reduction of dynamic power dissipation by about 20%, reaching ∼0.8 aJ bit operation. Two types of demonstration eSFQ circuit, shift registers and demultiplexers (deserializers), were implemented using the standard HYPRES 4.5 kA cm−2 fabrication process. In this paper, we present eSFQ circuit design and demonstrate the viability and performance metrics of eSFQ circuits through simulations and experimental testing.