Quantum Nanowires Slash Electrical Noise, Opening New Path for Ultralow-Noise Electronics
Flicker Noise Explained at the Smallest Scales
That familiar low-frequency fuzz that disrupts mobile phone calls stems from the way electrons move and interact within materials at the smallest scales. Known as electronic flicker noise, it typically arises when the flow of electrons is interrupted by various scattering processes inside conductive metals.
The same type of noise undermines the sensitivity of advanced sensors and poses a significant challenge for quantum computers—machines expected to deliver unbreakable cybersecurity, perform vast calculations and simulate nature in unprecedented ways.
UCLA Study Reveals a Quieter Quantum Transport Regime
Now, a far quieter and more promising future may be emerging. In a study led by UCLA, researchers have demonstrated prototype devices that, beyond a certain voltage, conduct electricity with less noise than is seen in ordinary electron flow.
The experimental devices were built from unconventional materials fashioned into nanowires—ribbons so slender that more than a thousand would be needed to equal the width of a single human hair. Unlike traditional electronic components, where noise levels typically remain unchanged, these nanowires displayed an unexpected trait: electrical noise fell as the current increased.
This behaviour stems from a quantum effect in which electrons move in step with phonons, the heat-driven vibration usually responsible for flicker noise. Crucially, one of the materials tested suppressed noise even at room temperature and above.
"Phonons are usually seen as the villains, scattering electrons and creating noise," said Alexander Balandin, corresponding author and Fang Lu Endowed Chair in Engineering at UCLA. "In this case, they actually enabled electrons to move together. This unusual property could significantly improve the signal-to-noise ratio." The findings were published in Nature Communications.
Electrons Surf the Wave
When a voltage is applied to a metal wire, electrons are driven by the electric field but are continually knocked off course by phonons and structural defects, producing a noisy electrical current.
The researchers exploited a very different mode of transport, triggered under specific quantum-mechanical conditions, in which electrons move collectively rather than independently. In this regime, electrons form periodic groupings through their interaction with phonons, becoming largely synchronized with these vibrations.
A helpful analogy is to imagine electrons as surfers moving across the ocean of a conducting material, with phonons acting as travelling waves.
In conventional transport, electrons resemble inexperienced surfers, frequently thrown off balance by the waves. In the quantum-driven mode, they behave like seasoned surfers, riding the phonon waves and using their energy to glide smoothly forward.
The close coupling between phonon vibrations and electron motion places these materials in a category known as strongly correlated materials, where electrons no longer behave independently.
"We were able to exploit this collective, correlated movement of electrons to significantly suppress noise," explained Alexander Balandin, vice chair for graduate education in UCLA's materials science and engineering department and director of the BMS Facility at the California NanoSystems Institute.
Turning Down the Noise Requires Rethinking Theory
The researchers fabricated nanowires from materials whose atomic bonds are strong along just one direction, before connecting them to microscopic electrodes.
One of these quasi one-dimensional nanowires was made from a tantalum-based compound, using the blue-grey metal commonly found in electronic components. The second quasi-1D material was derived from niobium, a closely related chemical element.
In the tantalum-based nanowire, electrical noise steadily declined as current increased, eventually dropping below practical measurement limits at temperatures of around -100 degrees Fahrenheit.
The niobium-based nanowire showed a similar trend: noise fell well below the level produced by ordinary electron transport and then stabilized, even in experiments conducted at room temperature and above.
The findings came as a surprise. In previous studies of other strongly correlated materials, or under different voltage conditions, noise levels had always rebounded to those seen in normal electron flow.
To confirm their results, the team built additional devices and developed new theoretical models to explain the unexpected behaviour.
"Strongly correlated materials are reshaping the landscape of materials science," Balandin said. "Our earlier, simplified descriptions overlooked many important properties, making it necessary to rethink our theoretical models and interpretations. By describing these materials with greater accuracy, we can uncover and better understand entirely new behaviours."
Implications for Quantum Computing and Future Electronics
The results point to real-world applications in:
- Next-generation ultralow-noise communications
- High-sensitivity sensing technologies
- More stable quantum computing components
They could also help stabilize the notoriously building blocks of quantum computers— without relying on the extreme cryogenic temperatures currently required.
Balandin imagines a future where strongly correlated materials serve as conductors linking components on computer chips, potentially enabling a fundamental rethink of circuit design.
"All good things eventually come to an end," he said. "As demand surges for high-performance, high-power computing driven by artificial intelligence, we must start exploring materials that, a decade from now, could offer alternative ways to transmit and process electrical signals."
The team plans to deepen its investigation of the materials featured in this study, while also searching for others capable of carrying charge-density waves even more efficiently at room temperature.
"There may be materials that outperform what we have seen so far," Balandin added. "The search is now under way."
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