Shapiro steps – a series of abrupt jumps in the voltage–current characteristic of a Josephson junction that is exposed to microwave radiation – have been observed for the first time in ultracold gases by groups in Germany and Italy. Their work on atomic Josephson junctions provides new insights into the phenomenon, and could lead to a standard for chemical potential.

In 1962 Brian Josephson of the University of Cambridge calculated that, if two superconductors were separated by a thin insulating barrier, the phase difference between the wavefunctions on either side should induce quantum tunneling, leading to a current at zero potential difference.

A year later, Sidney Shapiro and colleagues at the consultants Arthur D. Little showed that inducing an alternating electric current using a microwave field causes the phase of the wavefunction on either side of a Josephson junction to evolve at different rates, leading to quantized increases in potential difference across the junction. The height of these “Shapiro steps” depends only on the applied frequency of the field and the electrical charge. This is now used as a reference standard for the volt.

Researchers have subsequently developed analogues of Josephson junctions in other systems such as liquid helium and ultracold atomic gases. In the new work, two groups have independently observed Shapiro steps in ultracold quantum gases. Instead of placing a fixed insulator in the centre and driving the system with a field, the researchers used focused laser beams to create potential barriers that divided the traps into two. Then they moved the positions of the barriers to alter the potentials of the atoms on either side.

Current emulation

“If we move the atoms with a constant velocity, that means there’s a constant velocity of atoms through the barrier,” says Herwig Ott of RPTU University Kaiserslautern-Landau in Germany, who led one of the groups. “This is how we emulate a DC current. Now for the Shapiro protocol you have to apply an AC current, and the AC current you simply get by modulating your barrier in time.”

Ott and colleagues in Kaiserslautern, in collaboration with researchers in Hamburg and the United Arab Emirates (UAE), used a Bose–Einstein condensate (BEC) of rubidium-87 atoms. Meanwhile in Italy, Giulia Del Pace of the European Laboratory for Nonlinear Spectroscopy at the University of Florence and colleagues (including the same UAE collaborators) studied ultracold lithium-6 atoms, which are fermions.

Both groups observed the theoretically-predicted Shapiro steps, but Ott and Del Pace explain that these observations do not simply confirm predictions. “The message is that no matter what your microscopic mechanism is, the phenomenon of Shapiro steps is universal,” says Ott. In superconductors, the Shapiro steps are caused by the breaking of Cooper pairs; in ultracold atomic gases, vortex rings are created. Nevertheless, the same mathematics applies. “This is really quite remarkable,” says Ott.

Del Pace says it was unclear whether Shapiro steps would be seen in strongly-interacting fermions, which are “way more interacting than the electrons in superconductors”. She asks, “Is it a limitation to have strong interactions or is it something that actually helps the dynamics to happen? It turns out it’s the latter.”

Magnetic tuning

Del Pace’s group applied a variable magnetic field to tune their system between a BEC of molecules, a system dominated by Cooper pairs and a unitary Fermi gas in which the particles were as strongly interacting as permitted by quantum mechanics. The size of the Shapiro steps was dependent on the strength of the interparticle interaction.

Ott and Del Pace both suggest that this effect could be used to create a reference standard for chemical potential – a measure of the strength of the atomic interaction (or equation of state) in a system.

“This equation of state is very well known for a BEC or for a strongly interacting Fermi gas…but there is a range of interaction strengths where the equation of state is completely unknown, so one can imagine taking inspiration from the way Josephson junctions are used in superconductors and using atomic Josephson junctions to study the equation of state in systems where the equation of state is not known,” explains Del Pace.

The two papers are published side by side in Science: Del Pace and Ott.

Rocío Jáuregui Renaud of the Autonomous University of Mexico is impressed, especially by the demonstration in both bosons and fermions.  “The two papers are important, and they are congruent in their results, but the platform is different,” she says. “At this point, the idea is not to give more information directly about superconductivity, but to learn more about phenomena that sometimes you are not able to see in electronic systems but you would probably see in neutral atoms.”

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MILAN — OroraTech has entered a multi-year partnership with Kepler to supply thermal sensors for Kepler’s new optical communications constellation.  The first four SAFIRE Gen4 sensors under the agreement launched Jan. 11 aboard a Falcon 9, flying as part of the constellation’s initial deployment. “With Kepler, we are doing something completely new that will revolutionize […]

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A SpaceX Falcon 9 launched a trio of NASA astrophysics small satellites along with dozens of commercial spacecraft on a rideshare mission Jan. 11.

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Traditionally sleep coaches treat babies. But now more and more anxious, screen-attached grownups are the ones who need nursing.

NASA plans to return four astronauts from the ISS to Earth early Jan. 15, about a week after one of them experienced a medical issue that prompted the shortened mission.

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The FCC approved a second tranche of 7,500 Starlink Gen2 satellites Jan. 9, expanding the size of SpaceX’s authorized next-generation constellation.

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SpaceX sweeps nine national security missions for SDA and NRO under NSSL Phase 3 Lane 1

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Scientists welcome GSK announcement that two trials succeeded—even though data are still lacking

Pete Hegseth praises U.S.-built satellites and rapid launch as Trump administration escalates pressure on legacy primes

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Learn about the overlap between archaic humans that once lived on the Indonesian island of Sulawesi and the modern humans that replaced them. 

Learn how fossil evidence shows that ceratopsians lived across Europe during the Late Cretaceous, challenging long-held assumptions about where horned dinosaurs evolved.

Learn how an endangered species that rarely has twins is caring for two newborns — and why the coming weeks matter most.

Meta will finance Oklo’s purchase of uranium for its reactors. It’s a massive vote of confidence for both the startup and nuclear power, but challenges remain.

Learn more about the whale bones originally thought to be woolly mammoths' and how the hunt for the youngest mammoth continues. 

Learn why for only the first time in 25 years, NASA has decided to end an International Space Station mission early for medical evacuation.

Discover how the first mass extinction put jawed fishes on the map, species that would later come to dominate animal life on the planet.

Commercial launch startup Landspace has secured formal contracts to launch satellites for China’s two main megaconstellation projects, helping to address a launch capacity bottleneck.

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While much insight has been gleaned from how grasshoppers hop, their gliding prowess has mostly been overlooked. Now researchers at Princeton University have studied how these gangly insects deploy and retract their wings to inspire a new approach to flying robots.

Typical insect-inspired robot designs are often based on bees and flies. They feature constant flapping motion, yet that requires a lot of power so the robots either carry heavy batteries or are tethered to a power supply.

Grasshoppers, however, are able to jump and glide as well as flap their wings and while they are not the best gliding insect, they have another trick as they are able to retract and unfurl their wings.

Grasshoppers have two sets of wings, the forewings and hindwings. The front wing is mainly used for protection and camouflage while the hindwing is used for flight. The hindwing is corrugated, which allows it to fold in neatly like an accordion.

A team of engineers, biologists and entomologists, analysed the wings of the American grasshopper, also known as the bird grasshopper, due to its superior flying skills. They took CT scans of the insects and then used the findings to 3D-print model wings. They then attached the wings to small frames to create grasshopper-inspired gliders finding that their performance was on par with that of actual grasshoppers.

They also tweaked certain wing features such as the shape, camber and corrugation, finding that a smooth wing actually produced gliding that was more efficient and repeatable than one with corrugations. “This showed us that these corrugations might have evolved for other reasons,” notes Princeton engineer Aimy Wissa, who adds that “very little” is known about how grasshoppers deploy their wings.

The researchers say that further work could result in new ways to extend the flight time for insect-sized robots without the need for heavy batteries of tethering. “This grasshopper research opens up new possibilities not only for flight, but also for multimodal locomotion,” adds Lee. “By combining biology with engineering, we’re able to build and ideate on something completely new.”

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At the beginning of 2026, it’s worth reflecting on the U.S. Space Force’s recent accomplishments. They include the creation of the Commercial Space Office and its Commercial Augmentation Space Reserve, a working capital fund to provide flexibility in providing MILSATCOM services and new acquisition approaches for Resilient GPS and Protected Tactical SATCOM. The list of […]

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America faces a choice in space: lead or follow. There’s no middle ground anymore. China is methodically executing a plan to dominate the moon and cislunar space. The question isn’t whether someone will control humanity’s next economic frontier — it’s whether that someone will be us or them. And if we want it to be […]

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Far from the icy Arctic, ancient South Americans hunted whales using whalebone tools

What if a chemical reaction, ocean waves or even your heartbeat could all be used as clocks? That’s the starting point of a new study by Kacper Prech, Gabriel Landi and collaborators, who uncovered a fundamental, universal limit to how precisely time can be measured in noisy, fluctuating systems. Their discovery – the clock uncertainty relation (CUR) – doesn’t just refine existing theory, it reframes timekeeping as an information problem embedded in the dynamics of physical processes, from nanoscale biology to engineered devices.

The foundation of this work contains a simple but powerful reframing: anything that “clicks” regularly is a clock. In the research paper’s opening analogy, a castaway tries to cook a fish without a wristwatch. They could count bird calls, ocean waves, or heartbeats – each a potential timekeeper with different cadence and regularity. But questions remain: given real-world fluctuations, what’s the best way to estimate time, and what are the inescapable limits?

The authors answer both. They show for a huge class of systems – those described by classical, Markovian jump processes (systems where the future depends only on the present state, not the past history – a standard model across statistical physics and biophysics) – there is a tight achievable bound on timekeeping precision. The bound is controlled not by how often the system jumps on average (the traditional “dynamical activity”), but by a subtler quantity: the mean residual time, or the average time you’d wait for the next event if you start observing at a random moment. That distinction matters.

The study introduces CUR, a universal, tight bound on timekeeping precision that – unlike earlier bounds – can be saturated and the researchers identify the exact observables that achieve this limit. Surprisingly, the optimal strategy for estimating time from a noisy process is remarkably simple: sum the expected waiting times of each observed state along the trajectory, rather than relying on complex fitting methods. The work also reveals that the true limiting factor for precision isn’t the traditional dynamical activity, but rather the inverse of the mean residual time. This makes the CUR provably tighter than the earlier kinetic uncertainty relation, especially in systems far from equilibrium.

The team also connects precision to two practical clock metrics: resolution (how often a clock ticks) and accuracy (how many ticks before it drifts by one tick.) In other words, achieving steadier ticks comes at the cost of accepting fewer of them per unit of time.

This framework offers practical tools across several domains. It can serve as a diagnostic for detecting hidden states in complex biological or chemical systems: if measured event statistics violate the CUR, that signals the presence of hidden transitions or memory effects. For nanoscale and molecular clocks – like biomolecular oscillators (cellular circuits that produce rhythmic chemical signals) and molecular motors (protein machines that walk along cellular tracks) – the CUR sets fundamental performance limits and guides the design of optimal estimators. Finally, while this work focuses on classical systems, it establishes a benchmark for quantum clocks, pointing toward potential quantum advantages and opening new questions about what trade-offs emerge in the quantum regime.

Landi, an associate professor of theoretical quantum physics at the University of Rochester, emphasizes the conceptual shift: that clocks aren’t just pendulums and quartz crystals. “Anything is a clock,” he notes. The team’s framework “gives the recipe for constructing the best possible clock from whatever fluctuations you have,” and tells you “what the best noise-to-signal ratio” can be. In everyday terms, the Sun is accurate but low-resolution for cooking; ocean waves are higher resolution but noisier. The CUR puts that intuition on firm mathematical ground.

Looking forward, the group is exploring quantum generalizations and leveraging CUR-violations to infer hidden structure in biological data. A tantalizing foundational question lingers: can robust biological timekeeping emerge from many bad, noisy clocks, synchronizing into a good one?

Ultimately, this research doesn’t just sharpen a bound; it reframes timekeeping as a universal inference task grounded in the flow of events. Whether you’re a cell sensing a chemical signal, a molecular motor stepping along a track or an engineer building a nanoscale device, the message is clear: to tell time well, count cleverly – and respect the gaps.

The research is detailed in Physical Review X.

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‘Vanguard’ project builds on NASA-developed AutoNav under a $1.9 million SpaceWERX contract

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Aurora Therapeutics, cofounded by Nobel Prize–winning scientist Jennifer Doudna, plans to use gene editing and a new FDA regulatory pathway to commercialize treatments for rare diseases.