Cambridge researchers report a new breakthrough that could lead to the development of highly sensitive quantum sensors, which they say was achieved by exploiting tiny flaws in diamond fragments.
The discovery could pave the way toward innovative new applications that could help offer a deeper glimpse at neuron activity within living cells through magnetic imagery and other technologies.
Specifically, nanoscopic detectors capable of measuring temperature and magnetic fields could be inserted into living cells, allowing scientists an unprecedented glimpse at chemical reactions that occur on the cellular level. Beyond biology, the achievement also could have applications for helping scientists better understand the way certain unique materials gain their magnetic properties.
Flaws in diamonds that occur at the atomic scale can lead to unique and often beautiful color variations in certain rare kinds of diamonds. However, apart from their generation of precious stones, scientists view these impurities as a significant avenue for research in quantum physics.
An example of the kinds of flaws that interest scientists is what is known as the Nitrogen-vacancy Center, or NVC, where a gap exists in the crystal lattice of a diamond alongside nitrogen atoms. When this occurs, electrons become tightly contained, and scientists have learned that their spin states can be precisely manipulated.
In the past, scientists have succeeded in achieving electron coherence in the NVCs of larger diamonds. This phenomenon refers to the degree of interference between electrons emitted from a source such as an electron gun, which plays a key role in ultrafast chemistry and physics research.
Coherence times of up to one second—a significant amount for research in this field and the longest amount ever observed in any known solid material—have been achieved in the NVCs of larger diamond samples, whereas finding any amount of coherence in tiny diamonds measuring just a few nanometers has previously remained unattainable.
Achieving coherence in smaller diamonds, however, presents several advantages. One is the precision they would allow for applications at the nanoscale, as well as their ability to be inserted into living cells.
Now, researchers at Cambridge University say that the elusiveness of coherence in smaller diamonds has been identified as a concentration of nitrogen impurities instead of interactions with spins on the surfaces of the diamond.
The discovery, according to researchers at Cambridge’s Cavendish Laboratory, was made by observing the spin dynamics in nanodiamond NVCs. Independent control of the nitrogen impurities allowed the researchers to raise coherence times to 0.07 milliseconds longer than any previous attempt. The figure may sound minuscule, but it is orders of magnitude greater than past studies had ever achieved, paving the way toward nanodiamonds becoming a key material in the development of new quantum sensing technologies.
Researcher Helena Knowles, who participated in the study, said the results could ultimately lead to the development of the world’s smallest magnetic field detector, as well as the tiniest temperature detector ever made.
“Nanodiamond NVCs can sense the change of such features within a few tens of nanometres,” Knowles said in a statement. “[N]o other sensor has ever had this spatial resolution under ambient conditions.”
“We now have both high spin coherence and spatial resolution, crucial for various quantum technologies,” Knowles added.
Among the promising applications for such technology are non-invasive ways of detecting magnetic and temperature changes that occur within living cells, which the researchers compare to MRI scans that would allow them to monitor an individual cell’s reaction to stimuli, such as the introduction of a drug, in real-time.
Other areas of study, such as material science, could benefit from such technologies as well, the researchers say.
“Our work defines a paradigmatic class of magnetic systems to explore two-dimensional monopolar physics, and highlights the transformative role that diamond quantum magnetometry could play in exploring emergent phenomena in quantum materials,” the team writes.
The team’s research was detailed in a new paper published in Nature Materials on December 5, 2023.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.