Physicists surround the 178-year-old theory to cancel magnetic fields

The ability to cancel magnetic fields has benefits in quantum technology, biomedicine and neurology.

A team of scientists including two physicists at the University of Sussex has found a way to circumvent a 178-year-old theory that means they can effectively cancel out magnetic fields at a distance. They are the first to do so in a way that has practical benefits.

The work is hoped to have a wide variety of applications. For example, patients with neurological disorders such as Alzheimer’s or the possibility of Parkinson’s in the future getting a more accurate diagnosis. With the ability to cancel out ‘noisy’ external magnetic fields, doctors using magnetic field scanners will be able to see more accurately what is going on in the brain.

The study “Adaptation of magnetic fields in inaccessible regions” is published in Physical review letters. It is an international collaboration between Dr. Mark Bason and Jordi Prat-Camps at the University of Sussex, and Rosa Mach-Batlle and Nuria Del-Valle from the Autonoma de Barcelona University and other institutions.

Earnshaw’s Theorem of 1842 limits the ability to form magnetic fields. The team was able to calculate an innovative way to bypass this theory in order to effectively cancel out other magnetic fields which could confuse readings in experiments.

In practical terms, they achieved this by creating a device consisting of a careful adjustment of electrical wires. This creates additional fields and thus counteracts the effects of the unwanted magnetic field. Scientists have been struggling with this challenge for years, but now the team has found a new strategy to deal with these problem areas. While a similar effect has been achieved at much higher frequencies, this is the first time that it has been achieved at low frequencies and static fields – such as biological frequencies – which will unlock a host of useful applications.

Other possible future applications for this job include:

  • Quantum technology and quantum computing, in which ‘noise’ from external magnetic fields can affect experimental readings
  • Neuroimaging, in which a technique called ‘transcranial magnetic stimulation’ activates different areas of the brain through magnetic fields. Using the techniques in this paper, physicians may be able to more carefully treat areas of the brain that need stimulation.
  • Biomedicine, to better control and manipulate magnetic nanorobots and nanoparticles that move inside a body by means of external magnetic fields. Possible applications for this development include improved drug delivery and magnetic therapy of hyperthermia.

Dr. Rosa Mach-Batlle, lead author of the paper from the Autonoma de Barcelona University, said: “Given the fundamental question of whether or not it was possible to create a magnetic source at a distance, we came up with a strategy for controlling magnetism in distance that we believe can have a significant impact on technologies by relying on the distribution of the magnetic field in inaccessible regions, such as within a human body. “

Dr. Mark Bason of the School of Mathematical and Physical Sciences at the University of Sussex said: “We have discovered a way to bypass Earnshaw’s theorem that many people did not imagine was possible. As a physicist, this is quite exciting. But it is not just a theoretical exercise as our research could lead to some really important applications: more accurate diagnosis for patients with Neurone Motor Disease in the future, for example, better understanding of dementia in the brain, or accelerating development of quantum technology. “

Reference: “Tailoring magnetic fields in inaccessible regions” by Rosa Mach-Batlle, Mark G. Bason, Nuria Del-Valle and Jordi Prat-Camps, October 23, 2020, Physical review letters.
DOI: 10.1103 / PhysRevLett.125.177204

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