Imagine unlocking the secrets of atoms so precisely that it could revolutionize timekeeping and computing forever—this is the exciting frontier physicists have just stepped into!
Good neighbors aren't just a blessing in everyday life; they can even play a starring role in the microscopic world of atoms. A group of physicists from Amsterdam has made a groundbreaking leap by measuring a crucial trait of strontium atoms—the kind of element that's pivotal for cutting-edge tech like atomic clocks and quantum computers—with accuracy never seen before. Their clever trick? Leveraging a neighboring cloud of rubidium atoms. The findings hit the pages of Physical Review Letters this week (check it out here: https://link.aps.org/doi/10.1103/cjks-9hlp).
Strontium might not be the household name like gold or oxygen, but in the physics community, it's a rock star for good reason.
It's part of a select group of six alkaline earth metals, sharing traits with more familiar ones such as magnesium, calcium, and even radium. Each strontium atom packs 38 protons in its core, plus a fluctuating count of neutrons. Naturally occurring strontium comes in isotopes with neutron numbers of 46, 48, 49, or 50.
If you're into numbers, you might notice that 49 stands out as the only odd one. But here's where it gets controversial—this quirky oddity isn't just a fun fact; it's what makes one isotope of strontium exceptionally special. That particular version, with a total of 87 particles in its nucleus (38 protons plus 49 neutrons), behaves differently because of its odd neutron count. It classifies as a fermion, while the even-numbered ones are bosons. For beginners, think of fermions like antisocial particles that can't occupy the same state, and bosons as their more cooperative cousins that can bunch up.
And this is the part most people miss—the odd number gives the nucleus a spin, turning it into a tiny magnet. All subatomic particles spin, but in pairs of identical ones, spins often cancel out to zero. That's the case for the bosonic strontium isotopes: protons, neutrons, and electrons all balance to zero spin, making the whole atom neutral in that sense. But the fermionic one? Its nuclear spin doesn't zero out, endowing it with magnetic flair that's captivated scientists for ages.
Atomic clocks and quantum computers: Where strontium shines
Let's dive into the applications. The fermionic isotope, often called 87Sr for short, is a top contender for the next wave of atomic clocks—those ultra-precise optical clocks that rely on exact light frequencies atoms absorb or emit.
When an atom shifts between energy states, it releases or takes in light. For strontium, the sharpest frequency produces a vivid red light at 698 nanometers. But here's a twist: the bosonic atoms can't access this ideal transition due to their zero spin rules. Enter the nuclear spin of 87Sr—it bends those rules just right, allowing the transition at a super-stable frequency without going overboard. Plus, the strength of that tiny nuclear magnet is vital for clock performance.
This ties into the Zeeman effect, discovered by Dutch Nobel laureate Pieter Zeeman back in 1896. Originally, it explained how magnetic fields split electron energy levels in atoms, creating multiple light frequencies. But it applies to nuclei with spin too, where the magnet's strength dictates how much splitting occurs and the radio frequencies needed to flip the nucleus between states. Accurately knowing this helps fine-tune optical clocks.
Beyond clocks, 87Sr's nuclear spin splits its energy into ten even-spaced levels under a magnetic field. In quantum computing, where classical bits are zeros or ones, qubits can be both at once—a "0 and 1" superposition. But with ten states, we could use qudits, which mix "0 through 9," potentially supercharging quantum computers for tasks like simulating molecules or cracking codes faster than ever.
The g-factor: The key to unlocking strontium's potential
The Zeeman effect is central here, so physicists need to measure the nuclear magnet's strength precisely—the g-factor of 87Sr. This factor reflects the nucleus's magnetism and some shielding from surrounding electrons in the neutral atom. Calculating it exactly is tough, so direct measurement is essential.
Measurements from over 50 years ago were solid, but no upgrades followed—until now. A team of five from the University of Amsterdam and QuSoft quantum center boosted precision by a factor of 100.
The breakthrough stemmed from an unexpected path. Lead author Premjith Thekkeppatt, a Ph.D. student at the time and now a postdoc at Copenhagen's Niels Bohr Institute, shares: "We aimed to bond strontium and rubidium into molecules, but it was tricky. So, we explored keeping them close without mixing, using optical trapping."
Trapping 87Sr near rubidium didn't form molecules, but it enabled nuclear magnetic resonance—essentially, gauging the energy-splitting frequency. Rubidium's well-known properties calibrated the trap's magnetic field, yielding an ultra-precise g-factor for 87Sr.
A challenging benchmark—and what it means for the future
This new precision paves the way for finer strontium-based tech in clocks and quantum systems, and maybe more discoveries. Thekkeppatt notes, "Our work sets a tough standard for atomic theory models. We've proven this co-trapping method excels for measurements, sparking ideas for other atoms and uses."
For context, imagine quantum computers evolving from qubits to qudits—some argue this could make them exponentially more powerful, but others worry about the added complexity in error correction. Is this overhyping strontium's role, or a game-changer?
More details: Premjith Thekkeppatt et al, Measurement of the g Factor of Ground-State 87Sr at the Parts-per-Million Level Using Co-Trapped Ultracold Atoms, Physical Review Letters (2025). DOI: 10.1103/cjks-9hlp (https://dx.doi.org/10.1103/cjks-9hlp). On arXiv (2025): DOI: 10.48550/arxiv.2504.11242 (https://dx.doi.org/10.48550/arxiv.2504.11242)
Citation: Physicists achieve high precision in measuring strontium atoms using rubidium neighbor (2025, November 4) retrieved 4 November 2025 from https://phys.org/news/2025-11-physicists-high-precision-strontium-atoms.html
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