What Are Superconducting Quantum Interference Devices or SQUIDs?

Updated on March 9, 2020
1701TheOriginal profile image

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

Source

There is no denying the complexity of quantum mechanics, but that can become even more complicated when we bring electronics into the mix. This does give us interesting situations that have such implications we give them their own field of study. Such is the case with Superconducting Quantum Interference Devices, or SQUIDs.

The first SQUID was constructed in 1964 after work for their existence was published in 1962 by Josephson. This revelation was called a Josephson junction, a critical component to our SQUIDs. He was able to demonstrate that given two superconductors separated via an insulating material would allow for a current to be exchanged. This is very weird because by nature an insulator should prevent this from happening. And it does…directly, that is. As it turns out, quantum mechanics predicts that given a sufficiently small insulator, a quantum tunneling effect occurs that sends my current to the other side without actually traveling through the insulator. This is the wacky world of quantum mechanics in full force. Those probabilities of unlikely things do happen sometimes, in unexpected ways (Kraft, Aviv).

An example of a SQUID.
An example of a SQUID. | Source

SQUIDs

When we start combining Josephson Junctions in parallel, we develop a direct current SQUID. In this set-up, our current faces two of our Junctions in parallel, so the current splits down each path to preserve our voltage. This current would be correlated to the “phase difference between the two superconductors” with respect to their quantum wave functions, which has a relation to magnetic flux. Therefore, if I can find my current I could essentially figure out the flux. This is why they make great magnetometers, figuring out magnetic fields over a given area based on this tunneled current. By placing the SQUID in a known magnetic field, I can determine the magnetic flux going through the circuit via that current, as before. Hence the name of SQUIDs, for they are made of Superconductors with a split current caused by QUantum effects which results in an Interference of the phase changes in our Device (Kraft, Nave, Aviv).

Is it possible to develop a SQUID with just a single Josephson junction? For sure, and we call it a radio frequency SQUID. In this, we have our Junction in a circuit. By placing another circuit near this we can gain an inductance which will fluctuate our resonant frequency for this new circuit. By measuring these frequency changes I can then back track and find the magnetic flux of my SQUID (Aviv).

Source

Applications and the Future

SQUIDs have many uses in the real world. For one, magnetic systems often have underlying patterns to their structure so SQUIDs can be used to find phase transitions as our material changes. SQUIDs are also useful in measuring the critical temperature at which any superconductor at that or below such temperature will prevent other magnetic forces from impacting by countering with an opposite force courtesy of the current rotating through it, as determined by the Meissner effect (Kraft).

SQUIDs can even be useful in quantum computing, specifically in generating qubits. The temperatures needed for SQUIDs to operate are low since we need the superconductor properties, and if we get low enough then quantum mechanical properties become greatly magnified. By alternating the direction of the current through the SQUID I can change the direction of my flux, but at those supercool temperatures the current has probabilities of flowing in either direction, creating a superposition of states and therefore a means of generating qubits (Hutter).

But we have hinted at a problem with SQUIDs, and it is that temperature. Cold conditions are hard to produce, much less make available at a reasonable operating system. If we could find high-temperature SQUIDs then their availability and use would grow. A group of researchers from the Oxide Nano Electronics Laboratory at the University of California in San Diego set out to try and develop a Josephson junction in a known (but difficult) high temperature superconductor, yttrium barium copper oxide. Using a helium beam, researchers were able to fine-tune the nanoscale insulator needed as the beam acted like our insulator (Bardi).

Are these objects complicated? Like many topics in physics, yes they are. But it reinforces the depth of the field, the opportunities for growth, for learning new things otherwise unknown. SQUIDs are but one example of the joys of science. Seriously.

Works Cited

Aviv, Gal. “Superconducting Quantum Interference Devices (SQUIDs).” Physics.bgu.ac.il. Ben-Gurion University of the Negev, 2008. Web. 04 Apr. 2019.

Bardi, Jason Socrates. “Fabricating inexpensive, high-temp SQUIDs for future electronic devices.” Innovatons-report.com. innovations report, 23 Jun. 2015. Web. 04 Apr. 2019.

Hutter, Eleanor. “Not Magic…Quantum.” 1663. Los Alamos National Laboratory, 21 Jul. 2016. Web. 04 Apr. 2019.

Kraft, Aaron, and Christoph Rupprecht, Yau-Chuen Yam. “Superconducting Quantum Interference Device (SQUID).” UBC Physics 502 Project (Fall 2017).

Nave, Carl. “SQUID Magnetometer.” http://hyperphysics.phy-astr.gsu.edu. Georgia State University, 2019. Web. 04 Apr. 2019.

Questions & Answers

    © 2020 Leonard Kelley

    Comments

      0 of 8192 characters used
      Post Comment

      No comments yet.

      working

      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, owlcation.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://maven.io/company/pages/privacy

      Show Details
      Necessary
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Features
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Marketing
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Statistics
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
      ClickscoThis is a data management platform studying reader behavior (Privacy Policy)