Scientists discover new way to keep quantum spins coherent for longer

New study shows that electron spins—tiny magnetic properties of atoms that can store information—can be protected from decohering (losing their quantum state) much more effectively than previously thought, simply by applying low magnetic fields. Normally, these spins quickly lose coherence when they interact with other particles or absorb certain types of light, which limits their usefulness in technologies like quantum sensors or atomic clocks. But the researchers discovered that even interactions that directly relax or disrupt the spin can be significantly suppressed using weak magnetic fields. This finding expands our understanding of how to control quantum systems and opens new possibilities for developing more stable and precise quantum devices.

[Hebrew University] A new study from researchers at the Hebrew University of Jerusalem and Cornell University reveals a powerful new method to significantly suppress spin decoherence in alkali-metal gases, potentially revolutionizing quantum sensing and information technologies. The findings, published in Physical Review Letters, demonstrate an order-of-magnitude reduction in spin relaxation rates at low magnetic fields.

The study was led by Mark Dikopoltsev and Avraham Berrebi, under supervision of Prof. Uriel Levy from the Hebrew University’s Institute of Applied Physics and Nano Center. and Prof. Or Katz from Cornell University

Spin decoherence, the process by which quantum spin information is lost due to environmental interactions, is a key obstacle in the development of quantum technologies. This research specifically examined the decoherence of hot cesium spins, which are primarily affected by spin-rotation interactions during collisions with nitrogen molecules and through absorption of near-resonant light.

The team demonstrated that these decoherence effects can be dramatically suppressed by applying low magnetic fields—achieving an order-of-magnitude reduction in spin relaxation rates. This suppression extends beyond previously known regimes such as spin-exchange relaxation-free (SERF), showing that magnetic fields can also control mechanisms that relax electron spins, rather than just conserve them.

“Our results show that low magnetic fields are not just useful for avoiding decoherence from random, spin-conserving interactions,” said Dikopoltsev. “They can actively suppress more damaging relaxation processes, giving us a powerful tool for preserving spin coherence.”

This discovery enhances fundamental understanding of spin dynamics and provides new strategies for controlling quantum states in hot atomic vapors. It lays the groundwork for future advancements in atomic clocks, quantum memory, magnetometry, and other technologies where long spin coherence times are critical.