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Jun Ye Elected to the American Academy of Arts and Sciences

Steven Burrows — Thu, 23 Apr 2026 04:14:02 +0000

Jun Ye Elected to the American Academy of Arts and Sciences Steven Burrows Wed, 04/22/2026 - 22:14

Steven Burrows / JILA Science Communications Manager

JILA Fellow Jun Ye has been elected a Member of the American Academy of Arts and Sciences, one of the nation’s oldest and most prestigious honorary societies. His election recognizes his extraordinary contributions to physics and quantum science, including pioneering advances in optical atomic clocks, precision measurement, and quantum many-body physics.

Founded in 1780, the American Academy of Arts and Sciences honors excellence across the sciences, humanities, arts, and public affairs, and brings leaders together to address issues of national and global importance. Academy members span centuries of achievement, from early U.S. founders such as John Adams and Benjamin Franklin to generations of influential scientists, scholars, and public leaders. Today, the Academy includes more than 250 Nobel and Pulitzer Prize recipients.

Ye, who is also a professor of physics at the University of Colorado Boulder and a physicist at the National Institute of Standards and Technology (NIST), will be formally welcomed at the Academy’s 2026 Induction Weekend this October in Cambridge, Massachusetts. His election reflects the high regard in which he is held by peers across the physics community and underscores JILA’s enduring leadership in fundamental and applied quantum research.

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Jun Ye Elected Corresponding Member of the Austrian Academy of Sciences

Steven Burrows — Mon, 20 Apr 2026 18:11:48 +0000

Jun Ye Elected Corresponding Member of the Austrian Academy of Sciences Steven Burrows Mon, 04/20/2026 - 12:11

Steven Burrows / JILA Science Communications Manager

JILA Fellow Jun Ye has been elected a corresponding member abroad of the Austrian Academy of Sciences (Österreichische Akademie der Wissenschaften, OeAW), recognizing his internationally influential contributions to physics and quantum science. Election to the OeAW honors scholars whose work has had a profound impact well beyond Austria and reflects exceptional standing within the global research community.

Founded in 1847, the Austrian Academy of Sciences is the country’s leading non-university research institution and a prestigious learned society spanning the natural sciences, humanities, and social sciences. Election as a corresponding member abroad is reserved for distinguished scientists based outside Austria whose research excellence and leadership have shaped their field internationally.

Ye is widely recognized for pioneering advances in optical atomic clocks, precision measurement, and quantum many-body science. His work has set new benchmarks for timekeeping accuracy and has broad implications for fundamental physics, quantum technologies, and geodesy.

As part of the Academy’s 2026 elections, Ye has formally accepted the honor and will be welcomed at official OeAW events in Vienna later this year, including a ceremonial session for newly elected members. His election further highlights JILA’s strong tradition of international scientific leadership and collaboration.

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Breaking The Laser Stability Record Using New Crystalline Mirrors

Steven Burrows — Wed, 18 Feb 2026 15:25:03 +0000

Breaking The Laser Stability Record Using New Crystalline Mirrors Steven Burrows Wed, 02/18/2026 - 08:25

Bailey Bedford / Freelance Science Communicator

A Crystalline Coated 6cm Silicon Cavity. Image credit: Steven Burrows / JILA

In a mirror maze, finding yourself between two mirrors is designed to leave you disoriented and feeling a little unstable. In contrast, getting caught between two mirrors can be incredibly stabilizing for laser light. Scientists make lasers with incredibly stable frequencies by using optical cavities, which are mirrored chambers where light bounces back and forth hundreds of thousands of times.

Researchers at JILA have a long history of improving laser technologies and working with optical cavities. While pushing the limits of laser stability and precision, they have found a plethora of potential disturbances that they have to address to maintain stable frequencies. A tiny vibration, such as from a shaking pump in the lab, can negatively impact the operation of an optical cavity if unchecked.

A team of researchers, led by JILA and National Institute of Standards and Technology Fellow and University of Colorado Boulder Physics professor Jun Ye, has been pushing the limits of stable laser technology for more than two decades, and the team has seen signs that the natural motion of atoms that make up the mirror coatings limit their performance. Overcoming this effect and improving the stability of lasers could unlock new opportunities for experiments, like gravitational wave detectors, and improved technologies, like better atomic clocks.

So, the researchers sought an improved mirror coating. In recent experiments, Ye and his group have collaborated with a team led by Thomas Legero and Uwe Sterr at the Physikalisch-Technische Bundesanstalt in Germany; together, the researchers have tested a new style of crystalline mirror coating expected to mitigate the negative impact of the ways atoms collectively move in the mirror’s structure. In an article published in the journal Physical Review Letters on Jan. 20, 2026, they described the experiment and the unparalleled stability the new coatings allowed them to achieve.

“So far, it had never been demonstrated that these coatings can support superior performance at the state-of-the-art level,” says Dahyeon Lee, a JILA postdoctoral researcher and first author of the article. “This work actually shows that these crystalline coatings give you four times better performance than traditional mirror coatings, while at the same time demonstrating the lowest instability of all optical cavities.”

Optical cavities are so useful in making precision lasers because light wants to naturally fall into certain frequencies when it is trapped between two reflective walls. A particular distance between two mirrors will support certain frequencies while discouraging others. But any vibration of the mirrors or any stretching or contracting of the chamber can interfere with the process and prevent the light from settling precisely into a specific frequency.

Members of Ye’s lab have long ago addressed the most obvious disruptions—like the vibrations of the cooling system that is necessary to keep the cavity working optimally. By using excellent equipment and being vigilant about tamping down vibrations, they have reached a point where things normally run so smoothly that they can see signs of their performance being impaired by the collective motion of all the atoms making up the mirror coating used in the cavity. Inside any solid object, atoms aren’t perfectly still, but depending on the structure of the material, they can all coordinate their motion in particular ways. Certain disturbances of a laser can be dealt with just by averaging the laser’s frequency for a certain amount of time, but the collective movement of the atoms in the mirrors couldn’t be dealt with so easily.

“This is a very special experiment where you can think about both engineering and physics,” says Zoey Hu, a JILA graduate student and author of the article. “What we're really doing here sounds like a simple thing—you're just keeping two mirrors as stable as possible with respect to each other. But when it comes to doing just that one simple thing, there are actually so many little details you have to think about and address.”

To address the collective atomic motion, one of the details the team has considered is how atoms behave in different materials. The new crystalline mirror coatings are made of aluminum, gallium and arsenic and have a structure that keeps the atoms locked more tightly in place than the atoms in the established coatings, which are made from silicon dioxide and tantalum pentoxide and have a more amorphous structure. The strict crystalline structure of the new coatings means the atom’s collective motion experiences less natural loss of energy and fewer random fluctuations in their motion, which should improve the stability of the frequency in experiments.

To show that the coatings were competitive with existing state-of-the-art technologies, the group had to put in some work, including installing the mirror coatings in a high-quality silicon cavity, cooling the cavity down to its frigid optimal temperature (17 K) and ensuring that the system operated smoothly. All their efforts paid off, and the system delivered a more stable frequency than the established coatings could. The coatings require some additional effort to work with, but the results show that the effort can deliver increased stability when the need arises.

“With this technology, and because we already have some other nice cavities, we can show better performance than you could get from any other laser in the world,” says Ben Lewis, a JILA postdoctoral researcher and author of the article. “The crystalline coatings are harder to work with. They're more finicky. But if you want to push and get better performance, they're one of the ways that you can.”

Lewis went on to say that the frequency is tied to the average distance the light travels between reflections and that the stability of their laser frequency averaged over a period of 10 seconds translates into knowing the length of the light’s journey to less than 1 percent of the width of a proton.

Since the coatings produced such great results, the group combined them with another technique that is known to be useful in increasing the stability of a laser frequency when another laser at the same frequency is available. They performed a process, called optical frequency averaging, where two cavities are simultaneously used and the frequency is averaged together. The other cavity used conventional coatings, but its length is more than three times longer, which is an alternative approach to increasing a cavity’s frequency stability. They demonstrated that the technique could increase the resulting frequency stability even further.

The group also shared data they collected that showed how the frequencies of four cryogenic silicon cavities have slowly changed over time. These cavities, located at either JILA or PTB, achieve the best performance currently possible for stable lasers. The frequency observed for each cavity naturally drifts after it is assembled, but over time, the drifting slows down. The data showed the changes of two cavities with the new mirror coatings and two with the established coatings. The exact role the coatings play in producing the drift remains a mystery, but the new data provides clues and indicates that the cavities with new coatings stabilized more quickly than the more established coatings.

While the group has already set a new record for laser frequency stability with the setup, the team is optimistic that the approaches used in these experiments will deliver even better results in the future. They are continuing to observe the cavity with the new coatings to see how it behaves in the long run and to use the cavity in new experiments, including applying it to keeping time.

“We know these cavities are stable and may be much better than the traditional way of doing timekeeping,” Lee says. “We're trying to reimagine how timekeeping can be done in the future by using these silicon cavities as a stable ticking machine.”

JILA researchers, working with collaborators in Germany, demonstrated that new crystalline mirror coatings dramatically reduce atomic-level noise in optical cavities, enabling lasers with record‑breaking frequency stability. By outperforming traditional coatings by a factor of four, these mirrors open the door to more precise experiments and future advances in technologies such as atomic clocks and gravitational‑wave detection.

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Nuclear Clockwork: Experiments Highlight Reproducibility of Nuclear Transition Frequency

Steven Burrows — Fri, 06 Feb 2026 18:32:10 +0000

Nuclear Clockwork: Experiments Highlight Reproducibility of Nuclear Transition Frequency Steven Burrows Fri, 02/06/2026 - 11:32

Artistic representation of a ²²⁹Th nucleus hosted inside a CaF2 crystal experiencing a local electric field gradient. The ²²⁹Th nuclear electric quadrupole moment interacts with the electric field, leading to split energy levels. Image credit: Steven Burrows / JILA

To be useful, clocks need to be consistent. Imagine two spies who synchronize their watches; they rely on them agreeing days or months later, even if one of them must take a frigid hike through arctic tundra. In many experiments, scientists similarly require that their clock is accurate to a tiny sliver of a second and that it will work the same as their colleague’s clock on the other side of the world.

Currently, when keeping time really counts, scientists and engineers turn to atomic clocks. Atomic clocks use the physics that governs the interactions between electrons and light. They can be so accurate that they could run for tens of billions of years without getting off by a second. These clocks have been used for research, such as experiments studying quantum many-body physics and relativity, and have enabled technologies, including GPS. But scientists are not satisfied. Researchers are exploring the potential of nuclear clocks to use the same principles to deliver even more precise results or to fit into an even smaller device.

JILA has been a leader in atomic clock and nuclear clock research, and in 2024 a team of researchers, led by JILA and National Institute of Standards and Technology Fellow and University of Colorado Boulder Physics professor Jun Ye, reported crucial research where they measured the first high-resolution spectrum of the nuclear transition of thorium and determined the absolute frequency of the transition. Ye and other scientists hope these transitions of thorium nuclei will be the ticking hearts of future nuclear clocks. However, there is still a lot for scientists to learn before nuclear clocks have a chance at becoming the gold standard for precision time keeping. For instance, researchers need to understand how nuclear transitions respond to things like changes in temperature, make sure that nuclear clocks can be made with a shared reproducible frequency and determine if they remain reliable over extended periods of time.

In new experiments, Ye and his colleagues have looked at crystals containing thorium to better understand how they might be used in nuclear clocks, including testing three crystal samples many times over the course of a year to check if their properties unexpectedly fluctuated over that time. In an article published in the journal Nature on January 28, 2026, they described the stability of three crystals observed over the course of multiple months, how the crystals responded to temperature changes, and how the different concentrations of thorium in each crystal affected their properties. The results revealed that the crystals have a promising stability and reproducibility and provided insights into future experiments and how similar crystals might be incorporated into high quality clocks.

“Checking frequency reproducibility, both between different host crystals and over an extended period of time, is the first step towards a systematic evaluation of the performance of the nuclear clock,” says Ye.

The group studied three crystals fabricated by Thorsten Schumm’s lab at the Technical University of Vienna. Each crystal was made of calcium fluoride but with some of the calcium atoms replaced with thorium atoms. The crystals each contained different concentrations of thorium. When the thorium atoms are in their lowest energy quantum state, Ye’s group can observe how they interact with particular frequencies of light to make their nucleus jump to higher energy states. They found that there are five transitions that they can trigger with slightly different frequencies of light. The frequencies of these transitions are critical to using thorium in a nuclear clock.

“It’s critical that Thorsten’s lab has provided three different Thorium-doped crystals, which allowed us to study the line width broadening mechanisms and the level of line center reproducibility,” says Ooi.

These interactions and frequencies follow essentially the same physics as the transitions of atoms used in atomic clocks. However, the states of the nucleus are less sensitive to fluctuations of the electric and magnetic fields around them than the states of atoms. Additionally, the nuclear states can be used even when the atoms are embedded in a crystal, unlike the states used for atomic clocks; this difference allows a nuclear clock using a crystal to have a clearer signal by using many more of the relevant atoms while perhaps also being packaged in a smaller device.

Ye’s lab previously studied how one of these crystals behaved at three different temperatures. In the new article, they continued to look at that crystal along with two others with lower concentrations of thorium.

The researchers observed that over the course of the year the properties of the first crystal were stable. The two additional crystals demonstrated the same frequency as the first and also delivered reproducible results when repeated measurements were made months apart. The fluctuations the team observed were stable to around a tenth of a trillionth of the frequency of the measured transition and are limited by the experiment’s measurement precision. These results are promising for researchers to be able to use such crystals to fabricate reliable clocks.

“We are able to show that even over the span of almost a year, we can measure the nuclear transition frequency in these crystals over and over again, and they're very consistent,” says Tian Ooi, a graduate student at JILA and first author of the paper.
The team did find some variations in the crystals’ performances based on the concentration of thorium. While the thorium all interacted with light of the same wavelength, how precisely they responded to the specific frequency varied. The state’s transition will sometimes respond to nearby frequencies and the group defines this extended range of interaction frequencies as the “line width” of the transition.

The group found that the line widths were considerably wider than theoretical calculations had predicted and that they depended on the thorium concentration with greater amounts of thorium producing broader line widths. The researchers propose that the broadening of the width may be caused by the substitution of thorium creating a subtle microstrain in the crystal’s structure that influences the nuclear transitions by making the electric field vary unevenly inside the material.

“This was an unexpected surprise,” says Ooi. “People didn’t anticipate how large this microstrain effect would be.”

Further research is needed to explain the effect and determine if it can be eliminated. Minimizing the line width is a critical factor in designing a high-performance nuclear clock, but high concentrations will also help researchers get a clear signal. So, researchers need to understand this relationship and, if possible, produce crystals with narrower line widths.

The group also continued their research into how the nuclear transition of thorium varied with temperature. They took measurements at more temperatures than they previously had, and for all three crystals, they looked at both the transition that varied the most and the transition that varied least with changes in temperature. The researchers found that the frequencies of the crystals were consistent with each other and identified the point where the material’s changes in response to temperature shift from decreasing the frequency to increasing it, which is where the impact of any temperature fluctuation is smallest. This temperature will likely be the most practical temperature to keep the crystal at when operating a nuclear clock.

The experiments also let the team map out the response of the transition that varies the most with temperature. Based on the results, the researchers suggest that in the future nuclear clocks can monitor that more sensitive frequency to record the temperature so that fluctuations to the least sensitive transition can be rapidly corrected.

Now that the group has these insights, they plan to continue studying these crystals, investigate why the line widths vary between crystals and chart a path to a future with nuclear clocks as a valuable timekeeping tool.

“I think what this paper shows is that we're moving from measuring the clock transition to really investigating how good this clock can be,” Ooi says. “There’s still interesting things to figure out, but this is one of the big steps that we have to take to show that solid-state nuclear clocks are viable.”

_{The authors acknowledge funding support from National Science Foundation QLCI OMA-2016244, DOE quantum center of Quantum System Accelerator, Army Research Office (W911NF2010182), Air Force Office of Scientific Research (FA9550-19-1-0148), National Science Foundation PHY-2317149, and National Institute of Standards and Technology. Part of this work has been funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 856415) and the Austrian Science Fund (FWF) [Grant DOI: 10.55776/F1004, 10.55776/J4834, 10.55776/ PIN9526523]. The project 23FUN03 HIOC [Grant DOI: 10.13039/100019599] has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Program and by the Participating States. We thank the National Isotope Development Center of DoE and Oak Ridge National Laboratory for providing the Th-229 used in this work.}

JILA researchers have taken a major step toward realizing next‑generation nuclear clocks by studying how thorium‑doped crystals behave over time. In new experiments published in Nature, the team tracked the stability, temperature response, and reproducibility of three calcium‑fluoride crystals containing different concentrations of thorium. Over nearly a year of measurements, all three crystals demonstrated remarkably stable nuclear transition frequencies—an essential requirement for building reliable nuclear clocks.

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JILA Researchers Overturn 25-Year-Old Explanation of Benzene Formation in Space

Steven Burrows — Fri, 09 Jan 2026 18:21:00 +0000

JILA Researchers Overturn 25-Year-Old Explanation of Benzene Formation in Space Steven Burrows Fri, 01/09/2026 - 11:21

Bailey Bedford / Freelance Science Communicator

Interstellar formation of PAHs terminates at C6H5+. Image credit: Steven Burrows / JILA

Space is famously empty. The cold vacuum of space—or more specifically, the interstellar medium—lacks much of anything, including the air needed to conduct sound. But it isn’t quite completely empty. While it’s vacant compared to what we experience in daily life, there are occasional atoms and molecules spread throughout it.

Those atoms and molecules mean that there is chemistry in space, although it doesn’t always resemble the dense, warm reactions that routinely occur in a chemist’s test tubes. One aspect of chemistry in space that researchers are interested in is the formation of polycyclic aromatic hydrocarbons (PAHs), which are molecules of carbon and hydrogen that make a broad array of chemicals on earth and in the void of space. Researchers have seen signs of light interacting with a variety of these molecules in space and being absorbed—leaving a distinctive fingerprint in the remaining light that reaches Earth. These molecules are estimated to contain somewhere between a tenth and a quarter of the carbon spread across the interstellar medium, and the molecules’ foundational building blocks are benzene (C₆H₆)—a ring of six carbon atoms, each holding a hydrogen atom.

Since 1999, researchers have had a model that they thought explained how benzene formed from smaller molecules. However, the challenges of performing experiments at the low temperatures and densities involved in mimicking the conditions in the interstellar medium have meant that researchers have relied on their theoretical understanding of the process and haven’t thoroughly tested it in experiments.

Now, JILA Fellow and University of Colorado Boulder Physics Professor Heather Lewandowski and members of her lab have used tools developed in physics laboratories to recreate the necessary conditions and have investigated how the chemistry plays out. The team described their experiment in an article published in the journal Nature Astronomy in May 2025. When they tested the process, the first steps played out as expected, but then they were surprised to find that the benzene failed to form at the final step. Their results give scientists a new window into how chemistry occurs in the interstellar medium and reopens the question of how carbon gets caught up in PAHs throughout space.

The key to recreating the chemistry occurring in the interstellar medium was creating a vacuum in a chamber and using lasers to cool molecules and hold them in place in the vacated space. This required the researchers to look at just a small number of molecules and to set aside the beakers and test tubes that are stereotypical of chemistry and instead rely on large metal chambers, air pumps, laser beams and many mirrors and lenses.

“It's a laboratory full of lasers, and vacuum chambers, and optics,” Lewandowski says. “It fills up half a room to be able to cool down these hundred little molecules.”

Selecting the right color of laser and aligning the beams correctly allows the researchers to suspend—trap—particles in a vacuum chamber as well as cool them down through a process called laser cooling. Laser cooling relies on the fact that light can give atoms and molecules a shove to slow them down and that the interaction can be tailored to depend on how the particles are moving. Carefully applied, laser cooling can get molecules down to temperatures just above absolute zero.

“Laser cooling and trapping has really been in the domain of physicists,” Lewandowski says. “The nice thing about JILA is we have physicists and chemists working together. In my own group, we have both backgrounds, and so we have the tools now that can answer these questions that really chemists didn't have the technology to tackle and physicists didn't know it was an interesting question to answer.”

These techniques allow them to focus on a small number of molecules and get a close look at the interactions that normally are obscured in a chaos of many reactions occurring rapidly and simultaneously.

With the equipment creating the needed conditions, the group started following the proposed recipe for creating benzene in the interstellar medium. The recipe’s main ingredient is a molecule of two carbon atoms and two hydrogen atoms, called acetylene (C₂H₂). The first step is mixing acetylene with molecules containing two nitrogen atoms and one hydrogen atom (N₂H⁺). The nitrogen atoms can provide their hydrogen atom to create new molecules with two carbon and three hydrogen atoms. That opens the door to two more steps of interactions with acetylene molecules to produce a molecule with six carbon atoms and five hydrogen atoms (C₆H₅⁺)—just one hydrogen short of the target benzene ring. The exact behavior of this molecule is not thoroughly understood, but the established recipe proposed that it could form benzene by capturing a molecule made from a pair of hydrogens and then letting the excess atoms go.

The team supplied just enough of the needed ingredients in the chamber so that it was improbable that more than two molecules would be reacting at a time. Using laser cooling, they cooled the molecules in the chamber down to just a few degrees Kelvin. This setup let them recreate what happens when two lonely molecules finally come together in space and get the chance to interact.

The group repeatedly ran the experiment, stopping after different amounts of time to eject the cloud of molecules and check which molecules had been formed. They saw the mixture progress through the expected steps of the recipe. They observed increases of various molecules as they were created and then decreases as they were consumed in the construction of even larger molecules. But as they waited progressively longer and longer, they never caught sight of any benzene rings. The mixture in the chamber eventually just reached a steady amount of C₆H₅⁺, and the final step of the recipe failed to occur.

“Initially we were very confused—and a little irritated—because we could never get the final reaction to happen,” says JILA postdoctoral researcher G. Stephen Kocheril, the lead author of the paper.

After performing several runs of the experiment and analyzing the data, the team concluded that the expected chain of events wasn’t happening and there must be something else occurring to produce all the benzene in space.

“None of the models now actually predict what's out there,” Lewandowski says. “If you look at observations of how many of these molecules we have out there, no model works. So we sort of said, ‘this model isn't it.’ We don't have a new model yet; that's what we're working on now. So it was kind of big for the community because it changed how larger and larger carbon-containing molecules are formed in space.”

Moving beyond the old explanation gives chemists insights into how they should think about the formation of these molecules and provides astronomers with new clues about which molecules they should be keeping an eye out for if they want to understand the chemistry happening out in the interstellar medium.

JILA Fellow and University of Colorado Boulder Physics Professor Heather Lewandowski and members of her lab have shattered a 25-year-old theory about how benzene forms in the interstellar medium, revealing that the long-accepted chemical recipe doesn’t work under space-like conditions. Their groundbreaking laser-cooling experiments open a new chapter in understanding the origins of complex carbon molecules in the cosmos.

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Physicist Jun Ye named to Quantum 100 list

Steven Burrows — Fri, 12 Dec 2025 18:36:15 +0000

Physicist Jun Ye named to Quantum 100 list Steven Burrows Fri, 12/12/2025 - 11:36

Daniel Strain / ��Ҵ�ý�ƽ�� Strategic Communications

Jun Ye

This week, UNESCO named physicist Jun Ye to its Quantum 100 list—a catalogue of some of the top leaders around the world in the rapidly growing field of quantum science.

Ye holds the Monroe Endowed Professorship in Physics at ��Ҵ�ý�ƽ�� and is a fellow at JILA and the National Institute of Standards and Technology (NIST). Among other research goals, Ye has revolutionized how scientists measure time, developing quantum technologies that can track the passage of time with never-before-seen accuracy and precision.

Ye is “recognized for his curiosity and his hands-on approach to experimentation,” according to the Quantum 100 list. “He has built a world-class research program using light, atoms, molecules, and advanced optical tools to explore nature with unprecedented precision.”

The recognition is part of the 2025 International Year of Quantum Science and Technology, which marks the 100th anniversary of what scientists often consider the beginning of quantum mechanics.

“I love this remarkable piece of science, which connects profound secrets of nature to our growing capabilities of revealing them,” Ye said. “The Year of Quantum has further strengthened the ideal that collaboration among scientists will help us to harness quantum science for building better and more meaningful lives for all of us in the world.”

Ye earned his PhD from ��Ҵ�ý�ƽ�� in 1997 where he trained under Jan Hall, who went on to win a Nobel Prize in 2005. Ye returned to JILA in 1999 and has received numerous awards for his research, including the 2022 Breakthrough Prize in Fundamental Physics.

“We are thrilled that Jun Ye has been identified as one of the Quantum 100 as part of the International Year of Quantum Science and Technology,” said Senior Vice Chancellor for Research and Innovation and Dean of the Institutes Massimo Ruzzene. “Jun’s groundbreaking research, visionary leadership, and unwavering commitment to collaboration and mentorship have been instrumental in driving quantum innovation at ��Ҵ�ý�ƽ��, JILA, NIST and across the Front Range, setting a global standard of excellence.”

Ye leads several quantum research initiatives at JILA. They include the CUbit Quantum Initiative and the Quantum Systems through Entangled Science and Engineering (Q-SEnSE) center funded by the U.S. National Science Foundation.

At JILA, Ye pioneered the design of optical atomic clocks, devices that measure time by tapping the behavior of atoms and electrons. His lab’s clocks would neither gain nor lose a second over billions of years.

Ye and his team have also worked to transform insights into the quantum world into technologies that can improve people’s lives. His lab, for example, built laser-based devices that can analyze samples of human breath, screening people for COVID-19 infections and other health conditions.

The Quantum 100 list also includes Chris Monroe who earned his doctorate in physics from ��Ҵ�ý�ƽ�� in 1992 and whose investment established Ye’s endowed professorship.

UNESCO stands for the United Nations Educational, Scientific and Cultural Organization, a specialized agency of the UN focused on fostering peace, security, and human rights through international cooperation in education, science, and culture. It develops educational tools, promotes cultural heritage, works on scientific endeavors like climate change, and designates World Heritage Sites to preserve globally significant places.

UNESCO named physicist Jun Ye to its Quantum 100 list—a catalogue of some of the top leaders around the world in the rapidly growing field of quantum science.

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JILA and NIST Fellow Jun Ye Named Clarivate Highly Cited Researcher for 12th Consecutive Year

Steven Burrows — Thu, 13 Nov 2025 21:13:42 +0000

JILA and NIST Fellow Jun Ye Named Clarivate Highly Cited Researcher for 12th Consecutive Year Steven Burrows Thu, 11/13/2025 - 14:13

Steven Burrows / JILA Science Communications Manager

JILA and NIST Fellow Jun Ye has once again been recognized as one of the world’s most influential scientists. For the 12th year in a row, Ye has earned a place on the Clarivate Highly Cited Researchers list, an honor reserved for researchers whose work ranks among the top 1% of citations globally across their fields.

This distinction highlights Ye’s sustained impact on atomic, molecular, and optical physics, as well as his pioneering contributions to precision measurement and quantum science. His research has transformed technologies such as optical atomic clocks, setting new standards for timekeeping and enabling breakthroughs in navigation, telecommunications, and tests of fundamental physics.

Clarivate’s Highly Cited Researchers program identifies scientists who have demonstrated broad and significant influence, based on rigorous evaluation of citation data and expert analysis. In 2025, only about 1 in 1,000 researchers worldwide achieved this recognition, underscoring the exceptional nature of Ye’s achievement.

Ye’s continued presence on this list reflects not only his scientific excellence but also his leadership in advancing quantum research initiatives, including the CUbit Quantum Initiative and the Q-SEnSE institute, which are shaping the future of quantum technologies.

For more details on the Highly Cited Researchers program and its selection process, visit Clarivate’s official site.

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Entangled Time: Pushing Atomic Clocks Beyond the Standard Quantum Limit

Steven Burrows — Thu, 23 Oct 2025 16:24:51 +0000

Entangled Time: Pushing Atomic Clocks Beyond the Standard Quantum Limit Steven Burrows Thu, 10/23/2025 - 10:24

Steven Burrows / JILA Science Communications Manager

Artistic representation of an atomic clock breaking the Standard Quantum Limit. Image credit: Steven Burrows / JILA

Imagine you're trying to keep time by listening to a room full of people clapping. If everyone claps randomly, it’s hard to tell the rhythm. But if they clap in sync, the beat becomes clear and steady. Now imagine you could gently guide them to clap more in unison—not perfectly, but just enough to reduce the noise. That’s what JILA researchers have done with atoms in a clock.

Their results, published in Physical Review Letters, show that it’s possible to go beyond what’s known as the Standard Quantum Limit (SQL)—a fundamental barrier in quantum measurements—by using a technique called spin squeezing. This work could help improve everything from GPS systems to tests of gravity and the nature of the universe.

What Limits a Clock’s Precision?

Atomic clocks are among the most precise instruments ever built. They work by measuring the frequency of light that causes atoms to jump between energy levels. These transitions are incredibly stable, making them ideal for keeping time. But there’s a catch. Each atom behaves independently, and their random quantum behavior adds noise to the measurement. This randomness is what defines the Standard Quantum Limit. It’s like trying to hear a single beat in a noisy crowd.

To reduce this noise, scientists often increase the number of atoms. The more atoms you measure, the better your estimate—kind of like averaging more coin flips to get closer to 50/50. But packing too many atoms together causes them to interact in ways that shift the clock frequency, introducing new errors. So instead of adding more atoms, the JILA team tried something different: they made the atoms entangled.

Entanglement is a quantum connection between particles. When atoms are entangled, their random quantum behavior becomes linked—even if they’re not touching. In this experiment, the researchers used entanglement to make the atoms behave more like a team, reducing the noise in their collective signal.

This approach allows the clock to beat the SQL, achieving better precision without needing more atoms. It’s a clever way to get more information out of the same number of particles.

Entanglement through Nondemolition Measurement

To entangle the atoms, researchers Dr. Yang Yang, Maya Miklos, and their lab mates used a method called quantum nondemolition (QND) measurement. This means they could measure the atoms without disturbing them too much, like checking the temperature of soup without taking the lid off.

They trapped about 30,000 strontium atoms in a grid of laser light called a two-dimensional optical lattice. This setup holds the atoms in place and keeps them cold—less than a millionth of a degree above absolute zero. Cold atoms move less, which helps maintain their coherence and reduces unwanted interactions.

The atoms were placed inside an optical cavity, which bounces light back and forth to enhance its interaction with the atoms. By shining a special probe light into the cavity, the researchers could gently measure the atoms’ collective spin—a property related to their energy state—without collapsing their individual quantum states. The team also used a technique called spin echo to cancel out unwanted shifts caused by the probe light. This helped preserve the delicate quantum state of the atoms during the measurement.

This process “squeezes” the uncertainty in one direction, reducing the noise in the measurement. It’s like squeezing a balloon: the uncertainty gets smaller in one direction but bigger in another. For clocks, this trade-off is worth it because it makes the timing signal more precise when one measures along the squeezed direction.

Putting the Squeezed Clock to the Test

To see if their entangled clock really worked better, the researchers compared two groups of atoms in a “synchronous comparison” between two atomic ensembles. By comparing two clocks at the same time, they could cancel out common sources of noise—like fluctuations in the laser used to probe the atoms. This allowed them to isolate the improvement due to spin squeezing: they can compare the case where both samples are regular, unentangled atoms (called a coherent spin state, or CSS), to where each sample is prepared in a spin-squeezed state (SSS) to see the improved stability from spin squeezing.

They studied how precisely the clock comparison signal could be measured over time. The spin-squeezed clock showed a 2.0 decibel improvement beyond the Standard Quantum Limit. That might not sound like much, but in the world of precision measurement, it’s a significant step forward. They found that the spin-squeezed clock not only beat the SQL but also showed a 3.3 dB improvement over the unentangled clock. This confirms that the entanglement was not just a theoretical benefit—it made a real difference in the clock’s performance.

Over a 43-minute test, the clock reached a fractional frequency uncertainty of 1.1 × 10⁻¹⁸. That means it could detect a change in time as small as one second over the age of the universe. This is the most precise entanglement-enhanced clock ever demonstrated, proving that such entanglement could in the future help make the world’s best clocks even more precise.

Why Does This Matter?

This research is part of a broader effort at JILA to explore how quantum physics can improve measurement tools. JILA Fellows Adam Kaufman and James Thompson are also exploring the use of entanglement for better measurement precision. Atomic clocks are already used in GPS satellites, telecommunications, and tests of fundamental physics. Making them even more precise opens new possibilities. A key challenge is to demonstrate genuine quantum advantage where an entangled clock can reach a performance level superior to the best clock today.

For example, ultra-precise clocks can measure tiny differences in gravity across short distances. This could help scientists study how gravity affects quantum systems or even searches for new physics beyond Einstein’s theories.

The techniques developed in this study—like spin squeezing and QND measurements—could also be used in other quantum technologies, such as sensors and quantum computers. These tools rely on the same principles of coherence and entanglement to perform tasks that classical systems can’t.

Looking ahead, the team hopes to improve their system by using three-dimensional optical lattices, which offer even better control over the atoms. They’re also exploring new ways to amplify signals using time-reversal techniques and quantum optimization algorithms.

There is also growing interest in using entangled clocks to probe the interface between quantum mechanics and gravity. Recent studies together with JILA Fellow Ana Maria Rey and external collaborators at University of Innsbruck have explored how mass-energy equivalence and gravitational gradients affect entangled states, raising fundamental questions about the nature of time and space.

A New Chapter in Quantum Timekeeping

By using entanglement to reduce quantum noise, JILA researchers have taken a meaningful step toward the next generation of atomic clocks. Their work shows that it’s possible to go beyond traditional limits by carefully engineering both the quantum states of atoms and the tools used to measure them.

As clocks become more precise, they also become more sensitive to the world around them. This opens the door to new experiments in gravity, quantum mechanics, and the structure of space-time itself.

In the end, this research isn’t just about keeping better time—it’s about using time to explore the microscopic and macroscopic side of the universe in new ways.

This research is supported by the US Department of Energy, Office of Science, National Quantum Information, Science Research Centers, Quantum Systems Accelerator; National Science Foundation; V. Bush Fellowship; JILA Physics Frontier Center; and the National Institute of Standards and Technology.

In a new study, researchers led by JILA and NIST Fellow Jun Ye have shown how to make atomic clocks even more precise by leveraging entanglement. This allows the atoms to “tick” more in sync, reducing the randomness that usually limits how precisely we can measure time.

Their results show that it’s possible to go beyond what’s known as the Standard Quantum Limit (SQL)—a fundamental barrier in quantum measurements—by using a technique called spin squeezing. This work could help improve everything from GPS systems to tests of gravity and the nature of the universe.

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Building the quantum workforce of the future: A new study seeks the way

Steven Burrows — Wed, 08 Oct 2025 17:28:39 +0000

Building the quantum workforce of the future: A new study seeks the way Steven Burrows Wed, 10/08/2025 - 11:28

Daniel Strain / ��Ҵ�ý�ƽ�� Strategic Communications

In recent years, quantum technology companies have begun to pop up across the United States. These companies design technologies that tap into some of the unique properties of very small things like atoms and electrons. Such technologies include “quantum computers” that could one day discover previously unknown medications, or sensors that can detect signs of illness in a single puff of breath. But the growth of the industry also raises a major question, said physicist Heather Lewandowski, one of the project leads: How can the nation better prepare students to enter this uncharted industry?

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Tailoring Record-Breaking Laser Stability for Coordinating Precise Atomic Dances

Steven Burrows — Wed, 01 Oct 2025 16:22:35 +0000

Tailoring Record-Breaking Laser Stability for Coordinating Precise Atomic Dances Steven Burrows Wed, 10/01/2025 - 10:22

Bailey Bedford / Freelance Science Communicator

3D optical lattice clock platform for highfidelity quantum state engineering.

Image Credit: Steven Burrows / JILA

Light is incredibly useful in daily life. We use light to see objects and determine details about them. Light is similarly valuable in probing the quantum world. It is often critical for both observing quantum objects and interacting with them.

When scientists need to precisely control atoms or molecules, light is often the only tool for the job. Selecting the correct frequency—color—of laser light and projecting it in the right configuration allows scientists to detect, trap, and even manipulate individual quantum particles.

However, keeping a laser stable at the right frequency is challenging. Even the most stable lasers randomly shift to slightly different frequencies and experience noise—random spurts of different frequencies similar to static on a radio signal. This frequency noise is currently one of the main limitations of lasers in many experiments. As researchers improve lasers, the improvements reliably produce better experiments and technologies, including more precise atomic clocks and quantum computers that experience fewer errors.

“Every quantum scientist dreams of having a laser that can keep driving quantum systems without introducing errors,” says Lingfeng Yan, a graduate student at JILA.

A team of researchers, led by JILA and National Institute of Standards and Technology Fellow and University of Colorado Boulder Physics professor Jun Ye, took on the challenge of tailoring a laser system to an unprecedented level of stability and showing the improvements it could deliver for practical applications. Achieving this new level of stability required them to make multiple lasers work together.

In an article published in the journal Physical Review X on August 26, 2025, they described their laser setup and showing the improvements it could deliver for practical applications. They showed that the laser delivered practical advantages by putting many neutral atoms through their paces working as a qubit—the basic building block of a quantum computer—and achieving an unprecedented low error rate for the particular design of qubit used.

The bespoke laser was needed because lasers aren’t all equal. Even with the best available designs, lasers of some colors are more stable than others in particular situations, and it’s impossible for any particular laser to do every job.

Fortunately, researchers can impart the stability of one laser onto another. It is like a dance teacher who has one student who is perfect at keeping their timing no matter how long the dance and another who is great at performing the necessary steps but frequently speeds up or slows down randomly. The teacher pairs them up, and whenever they notice the student messing up, they remind them to follow the lead of their partner. Properly directed, the group exceeds the performance of the individuals.

The group has access to a laser that can stay stable for extended periods—a prima ballerina. The researchers decided to test how well they could do at transferring its stability to a less stable dancer—specifically a laser compatible with altering the quantum states of strontium atoms. Such lasers are used to manipulate strontium in certain atomic clocks and quantum computers.

The lab’s stable dancer was a laser cavity made from a silicon crystal. The crystal’s rigidity makes it very stable over extended periods of time, but it must be kept at frigid temperatures to not be negatively impacted by temperature fluctuations.

“It is one of the best lasers in the world,” says Yan, who is the first author of the paper. “It provides an excellent long-term stability, but it's a specialized cavity.”

The specialized design means it is expensive and works for just a specific set frequency. So, to get similar performance at other frequencies, the team needed to become dance instructors and get other lasers to follow the silicon cavity’s lead over the long term.

Unfortunately, you can’t just yell dance instructions to a laser. The researchers had to use a specialized tool, called a frequency comb, to coordinate their lasers. A frequency comb is a device that, instead of producing a single laser beam, produces many precise, evenly spaced frequencies of light. The regular spacing makes frequency combs ruler-like tools for comparing different lasers and maintaining the frequency spacing between them.

However, even with the silicon cavity and frequency comb in the loop, the final beam would still experience high-frequency noise that would impair its use. This is largely because even the silicon cavity contributes a little noise, including some introduced by vibrations from the necessary cooling equipment.

To tamp down this residual noise, the researchers added another cavity to the dance: a simpler cavity that operated at the same laser frequency used to manipulate the strontium atoms. The second cavity is less stable over long times but doesn’t need to be cooled and therefore doesn’t experience the remaining troublesome noise over shorter periods. This second cavity handled suppressing their high-frequency noise issues while letting the silicon cavity steer the frequency over the long term.

The team carefully coordinated the appropriate set of correction procedures and technological connections between the two cavities, the optical frequency comb and the final laser, but that was just the beginning. The group still needed to confirm if their laser setup worked as intended. Was the meticulously tailored custom laser actually stable and could it deliver improved results?

The team created a test for themselves: Shining the laser at strontium atoms. The atoms’ sensitivity to specific light frequencies made them a precision tool for checking exactly how the laser was behaving. The researchers essentially turned the atoms into a tool for measuring the laser-frequency noise of the laser.

In the test, the strontium atoms reacted to subtle fluctuations in the light and could catch details that are otherwise easily missed. For example, during one test, they discovered an unexpected spike in the noise despite the laser seeming to run correctly. They discovered the noise was because a device designed to prevent the silicon cavity from vibrating had accidentally been turned off.

“What we trust most are measurements of the atomic response,” says Max Frankel, a graduate student at JILA and a co-author of the paper. “Atomic measurement should have the final word on our laser frequency noise model.”

Their test confirmed that their new setup delivered the improved performance they had predicted. Then, they moved on to demonstrating the practical advantage of all their effort by using the laser to make the atoms perform as qubits in a standardized test.

Using the stabilized laser, they performed strings of many gates—the basic operations of quantum computers—on each of 3000 qubits. They used gates that essentially signal an atom’s quantum state to spin around to various positions, which physicists call performing state rotations. Then, the researchers performed the gate that should reverse the whole string of operations. As long as noise didn’t interfere, the laser guided all the qubits through the set of steps to the same final position. By analyzing how well the qubits returned to their initial state over many runs, the researchers determined how reliably the laser executed the gates on average. They established a new record for the fidelity achieved using a laser to optically manipulate neutral atoms to perform state rotations.

The results of their test also match well with their model of the laser noise, which they say suggest that further laser improvements will likely deliver even better results. The team says that other researchers should be able to use the same techniques to tailor lasers with different frequencies to have similar refined stability.

“Lasers are central to manipulating quantum systems, which are very sensitive to imperfections, so improving lasers benefits scientists and engineers all over the world.” says Stefan Lannig, a JILA postdoctoral researcher and co-author of the paper. “To benefit from many ideas put forward by modern science, we need to enhance our control over intricate quantum systems, which requires first improving our tools.”

Jun Ye's research group has developed a groundbreaking laser system with record-breaking stability, crucial for advancing quantum technologies. By combining a highly stable silicon cavity laser with a frequency comb and a secondary cavity tuned for strontium atoms, the researchers created a laser capable of manipulating quantum states with unprecedented precision. Their system significantly reduces frequency noise, a major hurdle in quantum experiments, and demonstrated its effectiveness by achieving a new fidelity record in quantum gate operations on 3000 neutral atom qubits. This innovation paves the way for more accurate atomic clocks and scalable quantum computing.

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