Applications of Josephson Junctions

the basis for the most promising 2019 quantum computing implementation: superconducting quantum computer
Josephson voltage standard: the most practical/precise Volt standard, which motivated the definition of the ampere in the 2019 redefinition of the SI base units
SQUID devices, which are:
- very precise magnetometer
- the basis for superconducting quantum computers

Table of contents
- Josephson voltage standard
- SQUID device
  - DC SQUID SQUID device

Josephson voltage standard

The most practical/precise volt standard.

It motivated the definition of the ampere in the 2019 redefinition of the SI base units

Quick NIST article about it: www.nist.gov/news-events/news/2013/04/primary-voltage-standard-whole-world (archive)

The wiki page en.wikipedia.org/wiki/Josephson_voltage_standard contains amazing schematics of the device, apparently made by the US Government.

SQUID device

Can be used as a very precise magnetometer.

There are high temperature yttrium barium copper oxide ones that work on liquid nitrogen.

Video 1.

Superconducting Quantum Interference Device by Felipe Contipelli (2019)

. Source. Good intuiotionistic video. Some points deserved a bit more detail.

Video 2.

Mishmash of SQUID interviews and talks by Bartek Glowaki

. Source.

The videos come from: www.ascg.msm.cam.ac.uk/lectures/. Vintage.

Mentions that the SQUID device is analogous to a double-slit experiment.

One of the segments is by John Clarke.

Video 3.

Superconducting Quantum Interference Devices by UNSW Physics (2020)

. Source.

An experimental lab video for COVID-19 lockdown. Thanks, COVID-19. Presented by a cute and awkward Adam Stewart.

Uses a SQUID device and control system made by STAR Cryoelectronics. We can see Mr. SQUID EB-03 written on the probe and control box, that is their educational product.

As mentioned on the Mr. SQUID specs, it is a high-temperature superconductor, so liquid nitrogen is used.

He then measures the I-V curve on an Agilent Technologies oscilloscope.

Unfortunately, the video doesn't explain very well what is happening behind the scenes, e.g. with a circuit diagram. That is the curse of university laboratory videos: some of them assume that students will have material from other internal sources.

youtu.be/ql2Yo5LgU8M?t=211 shows the classic voltage oscillations, presumably on a magnetic field sweep, and then he puts a magnet next to the device from outside the Dewar
youtu.be/ql2Yo5LgU8M?t=253 demonstrates the formation of Shapiro steps. Inserts a Rohde & Schwarz signal generator into the Dewar to vary the flux. The result is not amazing, but they are visible somewhat.