SQUID

(Inside Science) -- Meet the game-changing scientific device you’ve never heard of -- SQUID. No, not the slimy animal with tentacles that wrestles sperm whales in Moby Dick. We’re talking about an entirely different kind of squid.

You can find them in machines doctors use to monitor cardiac and brain activities. You can also find them in detectors geologists use to find underground oil and silver deposits.

“So, the basic concept that we’re going to be talking about is called the SQUID and that’s an acronym for superconducting quantum interference device,” said John Clarke from the University of California, Berkeley.

By taking advantage of a physical phenomenon known as the Josephson effect, named after physicist Brian David Josephson, who laid the theoretical groundwork for the effect in 1962, SQUIDS use a loop made of superconducting material to measure the smallest changes in a magnetic field. The result? A device that is sensitive to magnetic fields that are a thousand trillion times smaller than a typical refrigerator magnet. It’s so sensitive that it can even detect the tiniest magnetic signals from your heart or brain.

“Someone with an array of SQUIDS could tell whether or not you’re actually paying attention to what I’m saying,” said Clarke.

Since SQUIDS rely on superconductors to function, they’re relatively expensive and mostly only used for scientific research and medical applications. But as superconductor technology has become cheaper in recent years, we are starting to see SQUIDS being used in more and more areas, even for some commercial applications.

“This was a group in Australia, where they can use high transition temperature SQUIDS to measure the electrical connectivity of the subsurface of the ground down to maybe a kilometer or two. And this has been very successful, and it enabled them to find the largest deposit of silver ever found anywhere on Earth. It’s worth about $2 billion,” said Clarke.

SQUIDS have long been at the forefront of materials science research for characterizing the magnetic properties of new materials that gave us modern day computers and smart phones.

Now, more than 50 years later, scientists are still finding new ways to use the incredible sensitivity of SQUIDS. Some think it might one day help us catch a glimpse at perhaps the most elusive mystery in our universe -- dark matter.

“The idea is that you have these very sensitive superconducting sensors and SQUIDS on telescopes that are specifically designed to do this,” said Clarke.

SQUIDS may be the best chance scientists have to determine if a specific hypothetical form of dark matter exists or not. Known as hot dark matter, the proposed particles may interact with the photons left over from the Big Bang in a way that can be detected.

“The actual detector of the photons is called a transition-edge sensor. If a photon lands on the sensor, then there is a change in the current going through the SQUID and the SQUID responds and you can see it,” concluded Clarke.

If this interaction between dark matter and photons indeed causes a slight change in the photon’s wavelength, a SQUID can provide the sensitivity we need to detect this shift.