New breakthrough method to protect quantum spins from noise

(Press-News.org) Researchers have discovered a simple yet powerful way to protect atoms from losing information—a key challenge in developing reliable quantum technologies. By shining a single, carefully tuned laser beam on a gas of atoms, they managed to keep the atoms' internal spins synchronized, dramatically reducing the rate at which information is lost. In quantum sensors and memory systems, atoms often lose their magnetic orientation—or "spin"—when they collide with each other or the walls of their container. This phenomenon, known as spin relaxation, severely limits the performance and stability of such devices. Traditional methods to counteract it have required operating in extremely low magnetic fields and using bulky magnetic shielding. The new method sidesteps those constraints entirely. Instead of magnetically shielding the system, it uses light to subtly shift atomic energy levels, aligning the spins of the atoms and keeping them in sync, even as they move and collide. This creates a more resilient spin state that is naturally protected from decoherence. In lab experiments with warm cesium vapor, the technique reduced spin decay by a factor of ten and significantly improved magnetic sensitivity. This breakthrough demonstrates that a single beam of light can extend the coherence time of atomic spins, opening the door to more compact, accurate, and robust quantum sensors, magnetometers, and memory devices.

A team of physicists from the Hebrew University’s Department of Applied Physics and Center for Nanoscience and Nanotechnology, in collaboration with the School of Applied and Engineering Physics at Cornell University, has unveiled a powerful new method to shield atomic spins from environmental “noise”—a major step toward improving the precision and durability of technologies like quantum sensors and navigation systems.

The study, “Optical Protection of Alkali-Metal Atoms from Spin Relaxation,” by Avraham Berrebi, Mark Dikopoltsev, Prof. Ori Katz (Hebrew University), and Prof. Or Katz (Cornell University), has been published in Physical Review Letters and can potentially revolutionize fields that depend on magnetic sensing and atomic coherence.

Why This Matters

Atoms with unpaired electrons—such as those in cesium vapor—have a property of “spin”, strongly interact with magnetic fields and therefore be used for ultra-sensitive measurements of magnetic fields, gravity, and even brain activity. But these spins are notoriously fragile. Even the tiniest disturbance from surrounding atoms or container walls can cause them to lose their orientation, a process known as spin relaxation. Until now, protecting these spins from such interference has required complicated setups or worked only under very specific conditions.

The new method changes that.

Laser Light as a Shield

The researchers developed a technique that uses a single, precisely tuned laser beam to synchronize the precession of atomic spins in magnetic field—even as the atoms constantly collide with one another and their surroundings.

Imagine a scenario where hundreds of tiny spinning tops are confined within a box. Typically, the interactions between these tops can disrupt their spin configurations, causing the entire system to fall out of sync. This effect become much more dominate at high magnetic fields, as the tops process and change their orientation much more rapidly. However, a specific method utilizes light to maintain synchronization within the system, by addressing the differences in the various spin configuration, the light effectively keeps all the tops spinning in harmony, preventing disorder and enabling cooperative behaviour among the spinning entities even at high magnetic fields. This approach highlights the fascinating interplay between light and atomic spin dynamics.

The researchers achieved a ninefold improvement in how long cesium atoms maintained their spin orientation. Remarkably, this protection works even when the atoms are bouncing off special anti-relaxation-coated cell walls and experiencing frequent internal collisions.

Real-World Potential

This technique could significantly enhance devices that rely on atomic spins, including:

Quantum sensors and magnetometers used in medical imaging, archaeology, and space exploration Precision navigation systems that don’t rely on GPS Quantum information platforms where spin stability is key to storing and processing information Because the method works in “warm” environments and doesn’t require extreme cooling or complicated field tuning, it could be more practical for real-world applications than existing approaches.

A New Frontier in Atomic Physics

“This approach opens a new chapter in protecting quantum systems from noise,” said the researchers. “By harnessing the natural motion of atoms and using light as a stabilizer, we can now preserve coherence across a broader range of conditions than ever before.”

The research builds on decades of work in atomic physics, but this simple, elegant solution—using light to coordinate atoms—is a leap forward. It may pave the way for more robust, accurate, and accessible quantum technologies in the near future.

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