Superconducting logic

Superconducting logic refers to a new class of logic circuits that rely on the properties of superconductors to create resistance-less wires and ultrafast switches that do not rely on conventional CMOS transistors. A CPU built with superconducting logic has the potential to be 10-100 times more energy efficient than conventional CMOS logic.[1]

The extreme power efficiency of Superconductoring logic over conventional CMOS makes superconducting logic an enabling technology for exaflop computing. In 2014, it was estimated that an exaflop computer built in cmos logic is estimated to consume some 500 megawatts power. Superconducting logic has been proposed to allow for greater saving in power that could theoretically approach 1/10 to 1/100th the same power required compared to CMOS.[1]

When Superconducting logic is chilled to a few degrees above absolute zero, this technology becomes an attractive option for ultrafast CPU's, where operating speeds are measured in picoseconds and operating frequencies approach 770 GHz.[1]

Rapid single flux quantum logic (RSFQ)

Since the early 1990s the dominant technology for superconducting logic has been based on Rapid single flux quantum (RSFQ) logic, which relays bits of information in the form of short voltage pulses carried by tiny, speeding vortices of current. RSFQ has been used to build a number of specialized devices needed for high-throughput and numerically intensive applications, such as communications receivers and signal processing. But the design consumes too much power to be scaled up to processors that could compete with CMOS chips in high-end computers. To distribute current among gates, RSFQ relies on a network of bias resistors that can consume 10 times as much power as superconducting logic uses for computation.[1][2]

Energy-Efficient Single Flux Quantum Technology

ERSFQ/eSFQ is intended to reduce the power losses of RSFQ.[3] by replacing bias resistors with sets of inductors and Josephson junctions.[1]

Reciprocal Quantum Logic (RQL)

Reciprocal Quantum Logic (RQL) is a new kind of superconducting logic which attempts to fix some of the problems of RSFQ logic. RQL uses reciprocal pairs of quantized single magnetic flux pulses to encode classical logic bits.[2]

Data encoding in Reciprocal Quantum Logic (RQL) is done using integer units of the magnetic flux quantum. RQL gates require no bias resistors to operate and this allows them to dissipate several orders of magnitude less power then previous superconducting logic families. Major RQL gates include: AndOr, AnotB, Set/Reset (with nondestructive readout), which together from a universal logic set and provide memory capabilities.[2]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Superconductor Logic Goes Low-Power, IEEE spectrum, 22 Jun 2011
  2. ↑ 2.0 2.1 2.2 Superconducting Logic Circuits Operating With Reciprocal Magnetic Flux Quanta, University of Maryland, Oberg, Oliver Timothy, 2011
  3. ↑ Energy-Efficient Single Flux Quantum Technology. Mukhanov 2011

External Links