A breakthrough finding that was made as a result of a fortunate accident in the lab has important ramifications for the development of quantum computers and sensors in addition to solving a problem that has persisted for more than 50 years. A team of engineers at UNSW Sydney has achieved what a renowned scientist first said was achievable in 1961 but has eluded everyone since manipulating the nucleus of a single atom using just electric fields. Their findings were published today in Nature.
“This discovery means that we now have a pathway to build quantum computers using single-atom spins without the need for any oscillating magnetic field for their operation,” explains Andrea Morello, Scientia Professor of Quantum Engineering at UNSW. Additionally, we can employ these nuclei to find answers to fundamental quantum scientific puzzles or as incredibly accurate sensors of electric and magnetic forces.
The fact that an electric field can be used to regulate a nuclear spin rather than a magnetic field has significant ramifications. The rules of physics state that it is difficult to limit magnetic fields to extremely small regions since they tend to have a wide area of impact. This necessitates the use of big coils and high currents to generate magnetic fields. On the other hand, tiny electrode tips can produce electric fields, and those fields drop off extremely abruptly from there. This will greatly simplify the control of individual atoms used in nanoelectronic devices.
A new paradigm
The technology of nuclear magnetic resonance, which is widely employed in industries as diverse as mining, chemistry, and medicine, is being shaken up by the discovery, according to Prof. Morello. He claims that one of the most widely used techniques in contemporary physics, chemistry, and even medicine or mining is nuclear magnetic resonance. “Mining corporations employ it to analyze rock samples, while doctors use it to view the inside of a patient’s body in exquisite detail. The use of magnetic fields to regulate and detect the nuclei can be a drawback for some applications, despite how well everything works.
In order to clarify the distinction between manipulating nuclear spins with magnetic and electric fields, Prof. Morello compares it to a pool table.
He compares it to trying to move a certain ball on a pool table by raising and shaking the entire table when performing magnetic resonance. The targeted ball will be moved, but we’ll also move every other ball as well.
The invention of electric resonance is comparable to receiving a real pool stick to strike the ball exactly where you want it, according to one person.
Nicolaas Bloembergen, a magnetic resonance pioneer and Nobel Laureate, initially proposed using electric fields to regulate nuclear spins in 1961. Amazingly, Prof. Morello was absolutely ignorant that his team had solved this long-standing challenge.
Despite spending the last 20 years of my life working on spin resonance, Prof. Morello admits that he has never heard of nuclear electric resonance. “This phenomenon was rediscovered’ by total accident; I would never have thought to seek for it. Since the initial attempts to show it proved to be too difficult, the entire topic of nuclear electric resonance has essentially been inactive for more than 50 years.
Out of curiosity
The goal of the initial experiment was to perform nuclear magnetic resonance on a single antimony atom because this element has a large nuclear spin. Dr. Serwan Asaad, one of the study’s primary authors, explains: “Our initial objective was to research the boundary between the quantum world and the classical world, which is determined by the nuclear spin’s chaotic behavior. Without any practical purpose in mind, this was just a project done out of curiosity.
But as soon as we got going on the experiment, we realized something wasn’t right. According to Dr. Vincent Mourik, another main author of the article, “The nucleus behaved quite oddly, refusing to respond at certain frequencies but exhibiting a significant response at others.
We were perplexed by this for a time before realizing that we were performing electric resonance rather than magnetic resonance in a “eureka moment.”
In order to regulate the antimony atom’s nucleus, we constructed a device with an antimony atom and a specific antenna that was designed to produce a high-frequency magnetic field. We put a lot of power into the antenna and blew it up since our experiment needed a very strong magnetic field.
Game on
Normally, when you blow up the antenna with tiny nuclei like phosphorous, it’s “game over” and you have to throw the equipment away, claims Dr. Mourik.”However, the experiment continued to function with the antimony nucleus. It turns out that the antenna was producing a significant electric field after the damage rather than a magnetic field. Therefore, nuclear electric resonance was “rediscovered.”
The researchers employed advanced computer modeling to determine precisely how the electric field affects the spin of the nucleus after establishing their ability to regulate the nucleus with electric fields. Through the distortion of the atomic bonds surrounding the nucleus caused by the electric field, nuclear electric resonance was shown to be a really local, tiny phenomenon.
According to Prof. Morello, “This groundbreaking result will open up a treasure trove of discoveries and applications.” “The system we built has enough complexity to explore how the quantum world gives rise to the everyday classical world that humans perceive. Additionally, we may leverage its quantum complexity to create electromagnetic field sensors with significantly higher sensitivity. All of this is contained in a straightforward silicon-based electrical device that can be operated by applying very modest voltages to a metal electrode.
