To monitor the amount and type of nuclear material at power plants and weapons facilities, scientists look for

A material that normally blocks the flow of electricity can suddenly begin behaving like a metal when exposed to remarkably weak light, according to a new experiment involving one of the strangest forms of graphene ever created. The breakthrough reveals that an unusual quantum effect could eventually provide a new way to detect some of the faintest radiation around us.

Researchers working with “magic-angle” twisted bilayer graphene found that faint, long-wavelength radiation can effectively melt the material’s fragile correlated insulating state, causing its electrical resistance to plummet. Remarkably, the experiments showed that even relatively weak radiation could trigger a dramatic transition from an insulator to a metal.

Beyond revealing an unusual way that light can manipulate matter, the discovery could provide the foundation for extremely sensitive detectors capable of spotting faint terahertz and far-infrared radiation.

With further development, detectors operating at these wavelengths could have applications ranging from security imaging and material inspection to astronomy and environmental sensing.

The study, published in Nature Communications, centers on magic-angle twisted bilayer graphene, or MATBG—a material produced by stacking two sheets of graphene and rotating them relative to one another at a carefully controlled angle.

Under the right conditions, interactions between electrons can cause magic-angle graphene to enter exotic collective states, including superconducting and insulating phases.

“Here we show that this expectation does not apply to magic-angle twisted bilayer graphene (MATBG) and demonstrate giant photoresponse of MATBG to low-intensity long-wavelength photons when it is tuned to half filling of the moiré band,” researchers write. “Far-infrared photons selectively overheat the low-heat-capacity electronic subsystem, driving a collapse of the correlated order and producing a giant photoresistive response.”

Ordinarily, changing an insulator into a conductor with light requires supplying enough energy to alter how electrons can move through the material fundamentally. Previous experiments involving light-induced insulator-to-metal transitions have frequently depended on intense, ultrafast excitation.

Magic-angle graphene offers another route.

Twisting graphene sheets at carefully controlled angles creates a larger repeating structure known as a moiré superlattice, dramatically changing how electrons within the material interact. Those interactions have already produced some remarkable results.

As The Debrief reported last year, researchers studying magic-angle twisted trilayer graphene uncovered new evidence of unconventional superconductivity, including unusually tightly bound electron pairs and a distinctive superconducting energy gap.

That work was part of a greater effort to understand whether these exotic materials could eventually help scientists design superconductors capable of operating at much higher temperatures.

In the new study, researchers exploited another unusual state that can emerge in magic-angle graphene. At certain electron densities, interactions between electrons become unusually important, allowing them to organize into what physicists call a “correlated insulator.”

That collective state is extremely fragile. The correlated insulating gap exists at an energy scale of only a few millielectronvolts. Previous measurements cited by the researchers indicate that a gap of approximately 1 millielectronvolt at very low temperatures gradually closes as the material warms and disappears around 10 kelvin.

The researchers realized that weakness could become an advantage.

Their experimental device consisted of magic-angle graphene sandwiched between layers of hexagonal boron nitride and configured as a field-effect transistor. A graphite back gate allowed them to precisely control the number of charge carriers and tune the graphene into its correlated insulating state.

They then exposed it to millimeter-wave and far-infrared radiation.

Instead of needing to inject large numbers of charge carriers, the incoming photons heated the graphene’s low-heat-capacity electronic system. That relatively small temperature increase was enough to destabilize the cooperative electronic order, retaining the insulating state.

The gap collapsed, resistance dropped dramatically, and the material became metallic.

Measurements in darkness and under illumination reinforced that interpretation. Without radiation, the graphene displayed the temperature-sensitive resistance expected from an insulator. Under millimeter-wave illumination, it instead exhibited behavior representative of a metal.

Researchers compare the mechanism to superconducting bolometers, highly sensitive radiation detectors in which incoming energy interrupts a superconducting state. But their graphene device essentially operates in reverse: instead of destroying a zero-resistance state, approaching photons destroy a high-resistance correlated insulating state and turn it metallic.

That makes the insulator-to-metal transition more than an unusual demonstration of quantum physics. It becomes the detector’s signal.

The team found that the device responded across wavelengths ranging from 85 to 2,140 micrometers, encompassing far-infrared and millimeter-wave radiation.

That portion of the electromagnetic spectrum is particularly interesting because it can reveal things ordinary cameras cannot. Terahertz radiation can penetrate some materials opaque to visible light, while interactions between this radiation and matter can provide information about a material’s composition.

More capable detectors could therefore eventually contribute to technologies such as security scanners looking for concealed objects, systems inspecting manufactured components without cutting them open, or sensors identifying substances using characteristic spectral markers.

Astronomy offers another potential application. Cold dust, star-forming regions, and other objects that may be faint or obscured at visible wavelengths emit radiation in the far-infrared. Detecting those extremely weak signals requires exceptionally sensitive instruments, making improved detector technology valuable for future astronomical observatories.

The experimental graphene detector exhibited considerable intrinsic sensitivity. The researchers measured an internal voltage responsivity of approximately 17 million volts per watt of absorbed power. They note that its internal responsivity exceeds that of many commercial bolometers operating in the same spectral region.

However, researchers caution that practical external performance is presently limited partly by how efficiently radiation is absorbed, meaning the experimental device is not equivalent to a finished commercial detector. Better antennas, cavities, metamaterials, or other structures designed to funnel radiation into the graphene could potentially improve its performance considerably.

There are other hurdles. The effect currently requires ultra-low temperatures, and the unusually strong response depends upon generating high-quality magic-angle graphene structures. Those requirements mean practical security scanners or telescope cameras based on the technology remain prospective rather than imminent.

Still, there are encouraging characteristics. The photoresponse persisted at temperatures around 6 to 7 kelvin and remained robust in magnetic fields of several tesla, with substantial reduction appearing only above roughly 4 tesla. That magnetic-field tolerance could make the technology attractive for specialized scientific instruments where superconducting detectors may meet limitations.

The current device also has an estimated practical response time of roughly 50 nanoseconds, largely because of its electrical design. The underlying electron cooling occurs much faster, and researchers estimate that smaller devices could reduce that practical limit by at least an order of magnitude. They also envision twisted multilayer materials, wafer-scale growth, and large-format detector arrays as potential directions for future development.

For now, the experiment demonstrates that in certain quantum materials, changing electrical behavior does not necessarily require pumping large amounts of energy into individual electrons. Sometimes, a small amount of light only needs to destabilize the collective state that those electrons have constructed together.

For physicists, the discovery offers a new way to investigate how fragile collective states of matter collapse and recover. For engineers, that same fragility could become useful precisely because extraordinarily weak radiation can trigger an extraordinarily large electrical response.

“Our experiments can be further generalized for time-domain interrogation of the CI state itself,” researchers write. “Radiation-driven excitation confined within the flat band, combined with time-resolved monitoring of the CI photoresistance, would allow direct access to the intrinsic timescale of correlated-order suppression and recovery, thereby probing the collective dynamics within the ground state.”

Study: Elesin, L., Shilov, A. L., Kravtsov, M. et al. “Correlated Insulator Moiré Bolometer.” Nature Communications (2026).

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

Researchers in Japan have succeeded in measuring the temperature inside living cells with high precision using a new class of biocompatible quantum nanosensor – something that has been difficult to do until now even. If improved, the nanosensor could be used to characterize a wide range of biological phenomena and so help in disease diagnosis, they say.

Recent years have seen the advent of a new generation of nanoscale quantum sensors that can detect the tiny magnetic fields of biological systems. Some of these sensors rely on photons and others on electrons or spin defects – typically diamond specially engineered with nitrogen–vacancy (NV) defects. This material is made by removing two carbon atoms from the diamond lattice and replacing one with a nitrogen atom. The other “hole” is left empty, thereby creating a vacancy or defect. The spin state of the defect is influenced by the local magnetic field that can be “read out” from the way it fluoresces.

While a powerful tool, and biocompatible, this type of quantum sensor does suffer from certain limits. For one, it can be structurally inhomogeneous, which affects how it detects temperature and other physical or chemical parameters inside biological cells.

A more homogenous structure

Even though the new molecular quantum nanosensor (MoQN) works in the same way as these conventional devices, it does not suffer from this problem, explain Nobuhiro Yanai of the University of Tokyo and Hitoshi Ishiwata of the National Institutes for Quantum Science and Technology (QST), who led this research effort. This is because it has a more homogenous structure and does not contain any defects. Instead, it is made by embedding molecular spin qubits, in this case fabricated from pentacene, in nanocrystals of para-terphenyl. This design makes the structure uniform on a molecular scale and preserves the quantum coherence of the spin qubits. It is then coated with Pluronic F127, which is a biocompatible surfactant.

By detecting the spin direction of the “excited triplet state” of the pentacene qubits using a technique known as optically detected magnetic resonance (OMDR), the researchers can precisely determine the temperature of the qubits’ surroundings from the OMDR peak position. When they tested their method inside the cytoplasm of cancer cells in vivo, they found that the intracellular temperature was consistently higher than the surrounding medium.

Yanai says he embarked on this study after reading about the work of Sam Bayliss’ group at the UK’s University of Glasgow, and Ashok Ajoy’s group at the University of California, Berkeley in the US on OMDR in pentacene-doped para-terphenyl crystals. He says he immediately got the idea that nanocrystals of this material could be used for quantum sensing inside cells. This was because his group had already developed such nanocrystals for a different purpose in previous research.

Ensuring biocompatibility

“I then spoke with Hitoshi Ishiwata, who is an expert in quantum sensing using NV centres,” he recalls. “While many molecular qubits have been developed to date, there had been no examples demonstrating their sensing ability within living cells.”

The project required materials science expertise, he tells Physics World, and in particular, finding out how to reduce the material to the nanoscale and ensuring it was biocompatible.

“We already knew that nanodiamonds are good quantum sensors for temperature measurements, but I had noticed a practical limitation: their ODMR spectra often vary significantly from particle to particle,” he says. “This spectral dispersion can introduce errors, especially when trying to perform precise measurements at the single-particle level.”

Replacing hydrogen with deuterium

The researchers thought they had overcome this problem during the first run of their experiments because they found that different particles showed identical OMDR spectra. However, their joy quickly waned when they observed that the spectra were still broadened by hyperfine interactions between the pentacene-doped para-terphenyl molecules’ electron spins and hydrogen nuclear spins.

To improve the spectral resolution, Ishiwata says he suggested chemically modifying the molecule by replacing the hydrogen in it with deuterium. And the technique worked: “the hyperfine broadening was strongly suppressed, allowing us to determine the OMDR spectra much more precisely.”

These findings, which are detailed in Science Advances, show that MoQNs are a chemically versatile platform for quantum sensing in living cells and that they can operate directly inside them while maintaining the precision needed for absolute thermometry, he says. Their appeal also lies in in the fact that their structures can be easily modified.

It will not all be plain sailing, however, adds Yanai. MoQNs cannot yet target specific organelles within cells, so endowing them with this targeting capability is an important future challenge. “What is more, their size has been limited to around 200 nm so far, so creating smaller MoQN particles will be crucial,” he says.

The post Molecular spin sensor takes the temperature of cancer cells appeared first on Physics World.

In a groundbreaking stride toward the future of quantum technology, researchers have unlocked a new mechanism to control quantum emitters embedded in hexagonal boron nitride (hBN), a layered two-dimensional material. This breakthrough could serve as a critical leap forward in integrating quantum emitters into practical devices, bringing quantum computing, secure quantum communications, and ultra-sensitive quantum sensors closer to reality. This promising development emerged from meticulous experimental studies demonstrating the ability to reversibly tune the color and wavelength of light emitted by quantum defects in hBN simply by twisting its atomic layers.

Quantum emitters are nanoscopic sources of light that emit photons with quantum characteristics, pivotal for next-generation technologies reliant on quantum information processing. However, a formidable challenge in utilizing these emitters has been the difficulty in precisely controlling their optical properties post-fabrication. Dr. Angus Gale, the lead scientist behind this research, elucidated how their work provides an innovative “lever” by exploiting the intrinsic layered nature of hBN to adjust the quantum emission properties dynamically. Unlike traditional solid-state hosts such as diamond or silicon carbide, whose structures are rigid and three-dimensional, hBN’s atomically thin layers can be mechanically manipulated, lending itself to an unprecedented degree of tunability.

The team’s experiments demonstrated that by picking up, stacking, twisting, and restacking these ultra-thin hBN slices at varied angles, they could modulate the quantum emitters’ light emission dramatically. These shifts in wavelength were not minor perturbations but substantial changes far exceeding what has been typically achievable in similar solid-state quantum systems. This finding challenges the traditional paradigm which often seeks to stabilize quantum defect behavior within rigid host materials. Instead, the researchers embraced the inherent flexibility and twistability of hBN to realize a new class of quantum control.

Professor Igor Aharonovich, the supervising author, emphasized the broader implications of this twist-controlled modulation approach. He noted that coupling two-dimensional materials at specific twist angles opens up an entirely fresh set of physical phenomena that were previously inaccessible. By assembling layers with precision angular misalignment, new quantum states can emerge, potentially transforming the landscape of material engineering for quantum applications. This strategic layering and twisting, known as “twistronics,” has already inspired revolutionary advances in graphene-based systems, yet this study extends the concept into the realm of quantum emitters embedded in hBN.

One key advantage of using hBN is that its layered crystal structure allows researchers to systematically alter the interaction between layers, effectively tuning the electronic environment surrounding the defects responsible for quantum light emission. As Dr. Gale metaphorically illustrated, far from being a solid block, hBN behaves more like a stack of cheese slices. Just as peeling and recombining slices of cheese can change how flavors intermingle, twisting hBN slices changes the interaction between atomic planes, which in turn alters quantum emitter characteristics. This mechanical engineering at the nanoscale provides a versatile platform for on-demand tuning of quantum light sources.

This technology breakthrough is fundamentally experimental but holds widespread implications. Adjustable quantum emitters could accelerate the development of quantum computing hardware, where precise photon control is essential for encoding and manipulating qubits. Similarly, secure quantum communication protocols rely on tailored quantum light sources to guarantee the generation and distribution of entangled photons immune to interception. Moreover, quantum sensing that exploits the extreme sensitivity of quantum states to environmental changes stands to benefit significantly from tunable quantum emitters, pushing the boundaries of detection limits in fields ranging from medicine to navigation.

Another remarkable facet of the research is the ability to repeatedly pick up, twist, and restack hBN layers without degrading the quantum emitter properties. This reversibility enables iterative fine-tuning of device characteristics and might yield adaptable quantum systems reconfigurable post-production, a feature highly desirable from a technological deployment perspective. This contrasts sharply with permanent structural modifications used in conventional quantum emitter fabrication, which restrict adjustable control and device flexibility.

The team’s methodology involved sophisticated nanofabrication techniques and high-resolution optical spectroscopy to probe the quantum emitters’ response to twist-induced modifications. By correlating the angular misalignment with spectral shifts in emitted light, they constructed a detailed understanding of the underlying physics governing emission control. These insights provide a blueprint for engineering tailored quantum emitters with bespoke characteristics suitable for specific applications.

The research findings have been detailed in a paper published in the eminent journal Science Advances, signaling the scientific community’s enthusiasm for the potential unlocked by twistable quantum systems. Importantly, the authors have declared no competing interests, affirming the independent and foundational nature of this inquiry. Funded by the Australian Research Council and the Air Force Office of Scientific Research, the work highlights the vibrant collaboration between academic institutions and funding bodies committed to propelling quantum technologies.

This discovery heralds a new era in quantum material science, where layered two-dimensional crystals are no longer passive hosts but active tunable platforms. By harnessing the mechanical and electronic versatility of materials like hBN, researchers are gradually unlocking complex quantum phenomena with precision control previously deemed unachievable. The implications extend well beyond fundamental research, marking exciting progress toward quantum devices that could redefine computational power, information security, and sensory precision globally.

In summary, the twist-controlled modulation of quantum emitters in hexagonal boron nitride exemplifies the convergence of cutting-edge experimental physics and materials science innovation. By capitalizing on the unique layered architecture of hBN and the emerging discipline of twistronics, this research pioneers functional tunability in quantum light sources. As the scientific community continues to develop and refine these approaches, we edge closer to the practical implementation of quantum technologies that promise profound societal and technological transformation.

---

Subject of Research: Not applicable

Article Title: Twist-controlled modulation of quantum emitters in hexagonal boron nitride

News Publication Date: 19-Jun-2026

Web References: 10.1126/sciadv.aec0101

References:

• Gale, A., Aharonovich, I., et al. Twist-controlled modulation of quantum emitters in hexagonal boron nitride. Science Advances. 19 June 2026.

Keywords:
Quantum mechanics, Hexagonal boron nitride, Two-dimensional materials, Quantum emitters, Twistronics, Quantum light sources, Quantum computing, Quantum communication, Quantum sensing, Layered materials, Nanofabrication, Photonic modulation