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.