Brief introduction is given to Rapid Single Flux Quantum (RSFQ) electronics. It can be useful both for physicist and electrical engineer. Idea of classical superconducting computer is explained and such computer has also potential to be integrated with superconducting quantum computer.

1. Applications of Rapid Single Quantum Flux electronics
K.Pomorski, P.Prokopow
University of Warsaw, Jagiellonian University, Riken
kdvpomorski@gmail.com
February 11, 2014
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2. Overview
1 Motivation
2 General view of superconductivity
3 Josephson junctions
4 RSQF circuit elements
5 Perspectives
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3. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 3 / 57

4. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 4 / 57

5. Status of semiconductor electronics development
For four decades semiconductor electronics has followed Moores law: with
each generation of integration the circuit features became smaller, more
complex and faster. This development is now reaching a wall so that
smaller is no longer any faster. The clock rate has saturated at about 35
GHz and the parallel processor approach will soon reach its limit. The
prime reason for the limitation the semiconductor electronics experiences is
not the switching speed of the individual transistor, but its power
dissipation and thus heat.
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6. Motivation for Rapid Single Quantum Flux
Electronics(RSQF)
Digital superconductive electronics is a circuit- and device-technology that
is inherently faster at much less power dissipation than semiconductor
electronics. It makes use of superconductors and Josephson junctions as
circuit elements, which can provide extremely fast digital devices in a
frequency range dependent on the material of hundreds of GHz: for
example a flip-flop has been demonstrated that operated at 750 GHz.
This digital technique is scalable and follows similar design rules as
semiconductor devices. Its very low power dissipation of only 0.1 mikro W
per gate at 100 GHz opens the possibility of three dimensional
integration. Circuits like microprocessors and analogue-to-digital
converters for commercial and military applications have been
demonstrated. In contrast to semiconductor circuits, the operation of
superconducting circuits is based on naturally standardized digital pulses
the area of which is exactly the flux quantum φ0. The flux quantum is also
the natural quantization unit for digital-to-analogue converters.
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7. Discovery of superconductivity
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8. Superconductivity
Superconductivity is the transport of electric charge via the given material
without dissipation. It is characterized by the zero electric resistance,
expulsion of magnetic field from sample, macroscopic quantum effect
given by superconducting order parameter. The phenomena similar to
superconductivity is superfluidity, which is flow of liquid without any
viscosity.
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9. Ginzburg-Landau equations
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10. Abrikosov vortices
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11. Abrikosov vortices and flux quantization
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12. Tunneling Josephson junction
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13. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 13 / 57

14. DC SQUID definition
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15. Ramp edge JJ
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16. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 16 / 57

17. Stewart-McCumber parameter
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18. Strong damping case
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19. Various cases of Stewart-McCumber parameter
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22. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 22 / 57

23. Flux flow vs voltage drop
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24. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 24 / 57

25. Josephson transmission line
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26. Josephson transmission line circuit
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27. Essence of RSFQ
1. The first brick is responsible for the active transfer of SFQ pulses. It is
marked by a small inductance.
2. If we use a larger loop inductance between two junctions, the
circulating current is to small to flip the second junction and the
information is stored. This idea is used for building bistable cells.
3. Two read an arbitrary information in such a loop, we need a decision
element, namely the two junction comparator.
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28. Data representation in RSFQ
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29. DC/SQF interface
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30. Electrical parameters of DC/SQF interface
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31. Scheme of physical structure DC/SQF interface
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32. Top view of physical structure DC/SQF interface
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33. Simulations of signals in DC/SQF interface
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34. SFQ/DC interface
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35. Splitter
The Splitter doubles the SFQ pulses. When there is an input SFQ pulse
the splitter produced two output pulses at two different output ports. The
splitter is a non-storing cell like the JTL. Therefore it is also possible to
create the cell without using an optimization tool.
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36. DC/SFQ-JTL-SFQ/DC or delay ...
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37. CNOT in RSFQ
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38. OR in RSFQ
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39. T Flip Flop in RSFQ
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40. Circuit model and physical structure of RSFQ JJ
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41. Crosssection of RSFQ element
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42. Advantages of RSFQ
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43. Superconducting bolometer
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44. Comparison between sc and semiconductor detectors
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45. Superconducting processor
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46. Fluxonics foundary
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47. Fluxonics design
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48. Flux qubit readout
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49. Perspective of superconducting supercomputer
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50. Perspectives of RSFQ
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51. Maciej Zgirski work 1
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52. Maciej Zgirski work 2
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53. Maciej Zgirski work 3
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54. K.Pomorski, P.Prokopow (UW,UJ,RIKEN) RSQF electronics February 11, 2014 54 / 57

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56. References
K.K. Likharev and V.K. Semenov, IEEE Trans. Appl. Supercond. 1 (1991)
pavel.physics.sunysb.edu/RSFQ/Research/WhatIs/rsfqwte1.html
Rapid Single Flux Quantum Logic in High Temperature Superconductor
Technology, Ph.D. Thesis, University of Twente, Enschede, The Netherlands.
European roadmap on superconductive electronics-status and perspectives-Physica
C 2010
www.tu-ilmenau.de/en/department-of-advanced-
electromagnetics/research/superconductive-high-speed-electronics/rsfq-cell/
Possible existence of field induced Josephson junction, K.Pomorski, P.Prokopow
Mutual phase-locking in Josephson junction arrays, A.K. Jain, K.K. Likhareva, J.E.
Lukens, J.E. Sauvageau
Superconductor digital electronics,
rsfq1.physics.sunysb.edu/ likharev/personal/Hague.pdf
P. Bunyk, K. Likharev and D. Zinoview: ”RSFQ technology: physics and devices,”
in Int. Journal on High Speed Electronics and Systems, 2001
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57. The End
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