Building highly sensitive sensors of electromagnetic fields
A team of engineers at UNSW Sydney have discovered a method to control the nucleus of a single atom using electric fields instead of magnetic fields.
The breakthrough discovery enables the development of ultra sensitive atomic scaled sensors with applications across a range of industries.
That a nuclear spin can be controlled with electric, instead of magnetic fields, has major implications. Generating magnetic fields requires large coils and high currents, while electric fields, can be produced at the tip of a tiny electrode.
UNSW’s Scientia Professor of Quantum Engineering Andrea Morello says the discovery shakes up the paradigm of nuclear magnetic resonance.
“Nuclear magnetic resonance is one of the most widespread techniques in modern physics, chemistry, and even medicine or mining,” Professor Morello says.
“Doctors use it to see inside a patient’s body in great detail while mining companies use it to analyse rock samples. This all works extremely well, but for certain applications, the need to use magnetic fields to control and detect the nuclei can be a disadvantage.”
Magnetic fields are difficult to confine to very small spaces and tend to have a wide area of influence. Electric fields, on the other hand, make control of individual atoms placed in nanoelectronic devices much easier.
Professor Morello was completely unaware that his team had cracked the longstanding problem of finding a way to control nuclear spins with electric fields, first suggested in 1961 by a pioneer of magnetic resonance and Nobel Laureate, Nicolaas Bloembergen.
“I have worked on spin resonance for 20 years of my life, but honestly, I had never heard of this idea of nuclear electric resonance,” Professor Morello says. “We ‘rediscovered’ this effect by complete accident.”
After demonstrating the ability to control the nucleus with electric fields, the researchers used sophisticated computer modelling to understand how exactly the electric field influences the spin of the nucleus.
Their efforts highlighted that nuclear electric resonance is a truly local, microscopic phenomenon: the electric field distorts the atomic bonds around the nucleus, causing it to reorient itself.
“This landmark result will open up a treasure trove of discoveries and applications,” says Professor Morello.
“The system we created has enough complexity to study how the classical world we experience every day emerges from the quantum realm.
“Moreover, we can use its quantum complexity to build sensors of electromagnetic fields with vastly improved sensitivity. And all this, in a simple electronic device made in silicon, controlled with small voltages applied to a metal electrode.”