Differential SFQ transmission using either inductive or capacitive coupling

Abstract

The bias current requirement for RSFQ circuits is about an ampere per thousand gates. High current increases the thermal load of cables into the cryostat, produces undesirable currents and fields on-chip, and makes efficient power supply difficult. Series-biasing has been proposed, whereby the circuit is divided into blocks powered in series. This requires floating ground planes for each block, and differential signal propagation across ground plane boundaries where the blocks communicate. We have demonstrated transmission of pseudo-random data across a differential link using two distinct approaches, based on magnetic and capacitive coupling. For each circuit, we have measured data rates up to 30 Gb/s and bit error rates down to 10 10 . Bit error rates extrapolate to lower values. Inductive coupling was implemented in TRW's 4 kA/cm 2 Nb process, capacitive coupling in TRW's 8 kA/cm 2 process.

Stacked double-flux-quantum output amplifier

“…A low rate of switching errors in the DFQ driver has been demonstrated in other applications [9], [12], and is expected to apply in this context as well. A speed of 10 Gb/s was expected, but instead was limited to less than 1 Gb/s in test.…”

Energy dissipation minimization in Superconducting circuits

“…Both capacitive (Teh C.K., et al, 2004) and inductive methods (Kang J.H., et al, 2003) of coupling for current recycling have been demonstrated at a small scale. It is difficult to estimate the impact of the technique based on single gate operation as in (Johnson MW et al, 2003). Current recycling becomes easier at higher current density of the superconducting IC (Narayana S 2011).…”

The asynchronous rapid single-flux quantum electronics – a promising alternative for the development of high-performance digital circuits

“…All these negative effects can be more or less overcome by quantitative improvements of the currently existing RSFQ fabrication technologies and by application of new approaches for design of high-integrated RSFQ digital circuits (Kang and Kaplan, 2003;Johnson et al, 2003). Nevertheless, the design of large synchronous RSFQ circuits meets the speed of light as a fundamental physical limitation about the global synchronization.…”