# Josephson junction count

The Josephson junction count is the number of Josephson junctions on a superconducting integrated circuit chip. Josephson junctions are active circuit elements in superconducting circuits. The Josephson junction count is a measure of circuit or device complexity, similar to the transistor count used for semiconductor integrated circuits.
Examples of circuits using Josephson junctions include digital circuits based on SFQ logic (e.g., RSFQ, RQL, adiabatic quantum flux parametron), superconducting quantum computing circuits, superconducting analog circuits, etc.

## Integrated circuits

The superconducting integrated circuits listed here must have been fabricated and tested, but are not required to be commercially available. Chip area includes the full extent of the chip.
| Reference | Description | Junction count | Date | Maker | Process | Circuit [mm²] | Chip [mm²] |
| | RSFQ NOT gate | 13 | 1987 | Moscow State U. | 10 μm, 5 MA/m$^2$, 2 Nb | 1.1 | ? |
| CORE1α6 | RSFQ microprocessor, 8 bit | 6,319 | 2004 | NEC | 2 μm, 25 MA/m$^2$ | 10.9 | ? |
| SCRAM2 | RSFQ microprocessor, 8 bit | 8,197 | 2006 | SRL | 2 μm, 25 MA/m$^2$ | 15.3 | 25 |
| CORE1γ | RSFQ microprocessor, 8 bit | 22,302 | 2007 | ISTEC | 2 μm, 25 MA/m$^2$ | 40.45 | 64 |
| Rainier | RSFQ, 128 qubit QA processor | 23,360 | 2010 | D-Wave, SVTC | 250 nm, 2.5 MA/m$^2$, 6 Nb | 8 | 32 |
| Vesuvius | SFQ, 512 qubit QA processor | 96,000 | 2012 | D-Wave, SVTC | 250 nm, 2.5 MA/m$^2$, 6 Nb | 8 | 162 |
| | RSFQ, 16-bit adder | 12,785 | 2012 | SBU, AIST | 1 μm, 100 MA/m$^2$, 10 Nb | 8.5 | 29.75 |
| | 8,192 bit shift register | 32,800 | 2014 | SBU, MIT-LL | 500 nm, 100 MA/m$^2$, 8 Nb | 9 | 25 |
| Washington (W1K) | SFQ, 2048 qubit QA processor | 128,472 | 2015 | D-Wave, Cypress | 250 nm, 2.5 MA/m$^2$, 6 Nb | 30.3 | 136 |
| | RQL, 2 shift registers | 72,800 | 2015 | NGC, MIT-LL | 500 nm, 100 MA/m$^2$, 8 Nb | 9 | 25 |
| | 16000 bit shift register | 65,000 | 2017 | SBU, MIT-LL | 500 nm, 100 MA/m$^2$, 8 Nb | 12 | 25 |
| | 36000 bit shift register | 144,000 | 2017 | SBU, MIT-LL | 350 nm, 100 MA/m$^2$, 8 Nb | 15 | 25 |
| | 202280 bit shift register | 809,150 | 2017 | SBU, MIT-LL | 350 nm, 100 MA/m$^2$, 8 Nb | 64 | 100 |
| Pegasus P16 | SFQ, 5640 qubit QA processor | 1,030,000 | 2020 | D-Wave, SkyWater Technology | 250 nm, 2.5 MA/m$^2$, 6 Nb | 70.6 | ? |
Maker column may include organizations that designed and fabricated the chip.
Process column information: minimum linewidth, Josephson junction critical current density, superconducting layer number and materials. Conversions for units of critical current density: 1 MA/m$^2$ = 1 μA/μm$^2$ = 100 A/cm$^2$.

## Memory

Memory is an electronic data storage device, often used as computer memory, on a single integrated circuit chip. The superconducting integrated circuits listed here must have been fabricated and tested, but are not required to be commercially available. Chip area includes the full extent of the chip.
| Reference | Description | Junction count | Date | Maker | Process | Circuit [mm²] | Chip [mm²] |
| | 1024 bit ROM, NbN/MgO/NbN junctions | 5,943 | 1990 | Electrotechnical Lab, Japan | 3 μm, 5.6 MA/m$^2$, 2 Nb + 1 Pb-In | ? | 17.25 |
| | 4096 bit RAM | 23,488 | 2005 | ISTEC | 1 μm, 100 MA/m$^2$, 10 Nb | 5.5 | ? |