About the Ye Group

In a significant advance toward the future redefinition of the international unit of time, the second, a research team led by the National Institute of Standards and Technology (NIST) has compared three of the world’s leading atomic clocks with…
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Entangled particles have always fascinated physicists, as measuring one entangled particle can result in  a change in another entangled particle, famously dismissed as “spooky action at a distance” by Einstein. By now, physicists understand this…
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For the first time, researchers can turn on an electric field to manipulate molecular interactions, get them to cool down further, and start to explore collective physics where all molecules are coupled to each other.

Building on their newfound ability to induce molecules in ultracold gases to interact with each other over long distances, JILA researchers have used an electric “knob” to influence molecular collisions and dramatically raise or lower chemical…
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JILA researchers have used a state-of-the-art atomic clock to narrow the search for elusive dark matter, an example of how continual improvements in clocks have value beyond timekeeping.

A strangely shaped cloud of fermions revealed a record-fast way of cooling atoms for quantum devices.

Bringing molecules down to ultracold temperatures takes a mythic approach, but the Ye Group finds that their new scheme can hold up under tough conditions.

Using optical tweezers, the Kaufman and Ye groups at JILA have achieved record coherence times, an important advance for optical clocks and quantum computing.

New research from the Cornell Group suggests that the van der Waals universality may have limitations.

It's hard to read a clock with hands that wobble. The Ye Group has found a way to steady their optical atomic clock using a new cavity.

When the Ye group measured the total quantum state of buckyballs, we learned that this large molecule can play by full quantum rules. Specifically, this measurement resolved the rotational states of the buckyball,…
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Understanding chemistry requires understanding both molecules and quantum physics. The former defines the start and end of chemical reactions, the latter dictates the dynamics in between. JILA researchers now have a better understanding of both…
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With the advent of the laser, the fuzzy bands glowing from atoms transformed into narrow lines of distinct color. These spectral lines became guiding beacons visible from the quantum frontier. More than a half century later, we stand at the next…
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We all know what a tenth of a second feels like. It’s a jiffy, a snap of the fingers, or a camera shutter click. But what does 14 billion years–the age of the universe–feel like? JILA’s atomic clock has the precision to measure the age of the…
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The reaction, at first glance, seems simple. Combustion engines, such as those in your car, form carbon monoxide (CO). Sunlight converts atmospheric water into a highly reactive hydroxyl radical (OH). And when CO and OH meet, one byproduct is…
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Why are we here? This is an age-old philosophical question. However, physicists like Will Cairncross, Dan Gresh and their advisors Eric Cornell and Jun Ye actually want to figure out out why people like us exist at all. If there had been the same…
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Imagine A Future . . . The International Moon Station team is busy on the Moon’s surface using sensitive detectors of gravity and magnetic and electric fields looking for underground water-rich materials, iron-containing ores, and other raw…
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Researchers at JILA and around the world are starting a grand adventure of precisely controlling the internal and external quantum states of ultracold molecules after years of intense experimental and theoretical study. Such control of small…
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In the Ye group’s new quantum simulation experiment, cold strontium atoms, which are analogs of electrons, are allowed to tunnel between the pancakes that confine the atoms with laser light. Because the atoms moving in an array of pancakes are…
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Deborah Jin, Jun Ye, and their students wrote a review during the summer of 2016 for Nature Physics highlighting the accomplishments and future directions of the relatively new field of ultracold-molecule research. The field was…
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Using frequency comb spectroscopy, the Ye group has directly observed transient intermediate steps in a chemical reaction that plays a key role in combustion, atmospheric chemistry, and chemistry in the interstellar medium. The group was able to…
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The Ye group just solved a major problem for using molecular fingerprinting techniques to identify large, complex molecules: The researchers used an infrared (IR) frequency comb laser to identify four different large or complicated molecules. The…
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The old JILA molecule factory (built in 2002) produced the world’s first ultracold polar molecules [potassium-rubidium (KRb)] in 2008. The old factory has been used since then for ultracold chemistry investigations and studies of the quantum…
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The Ye and Rey groups have discovered the strange rules of quantum baseball in which strontium (Sr) atoms are the players, and photons of light are the balls. The balls control the players by not only getting the atoms excited, but also working…
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The Rey and Ye groups are in the midst of an extended collaboration on using the Ye group’s strontium (Sr) lattice clock for studies of spin-orbit coupling in pancake-like layers of cold Sr atoms. Spin-orbit coupling means an atom’s motion is…
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JILA’s cold molecule collaboration (Jin and Ye Groups, with theory support from the Rey Group) recently made a breakthrough in its efforts to use ultracold polar molecules to study the complex physics of large numbers of interacting quantum…
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The Ye group has just improved the accuracy of the world’s best optical atomic clock by another factor of three and set a new record for clock stability. The accuracy and stability of the improved strontium lattice optical clocks is now about 2 x…
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The Ye Group recently investigated what first appeared to be a “bug” in an experiment and made an unexpected discovery about a new way to generate high-harmonic light using molecular gases rather than gases of noble atoms. Graduate student Craig…
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Symmetries described by SU(N) group theory made it possible for physicists in the 1950s to explain how quarks combine to make protons and neutrons and JILA theorists in 2013 to model the behavior of atoms inside a laser. Now, the Ye group has…
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The Ye group has not only made two invisible rulers of extreme ultraviolet (XUV) light, but also figured out how to observe them with ordinary laboratory electronics. With this setup, the researchers were able to prove that the two rulers had…
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Imagine a network of multiple clocks orbiting the Earth, not only reporting down to us, but also collaborating quantum mechanically among themselves to operate precisely in sync as a single global superclock, or world clock. The world clock is…
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There’s exciting news from JILA’s ultracold molecule collaboration. The Jin, Ye, Holland, and Rey groups have come up with new theory (verified by experiment) that explains the suppression of chemical reactions between potassium-rubidium (KRb)…
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JILA and NIST labs are well on the way to creating astonishingly accurate optical atomic clocks based on the neutral atoms strontium (Sr) and ytterbium (Yb). The new technologies are already capable of the most meticulous timekeeping in human…
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Physicists wonder about some pretty strange things. For instance, one burning question is: How round is the electron? While the simplest picture of the electron is a perfect sphere, it is possible that it is instead shaped like an egg. The egg…
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Research associate Bo Yan and his colleagues recently observed spin exchanges in ultracold potassium-rubidium (KRb) molecules inside an optical lattice (a crystal of light formed by interacting laser beams). In solid materials, such spin…
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Because quantum mechanics is crucial to understanding the behavior of everything in the Universe, one can understand key elements of the behavior of a neutron star by investigating the behavior of an atomic system in the laboratory. This is the…
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The Ye group has opened a new gateway into the relatively unexplored terrain of ultracold chemistry. Research associate Matt Hummon, graduate students Mark Yeo and Alejandra Collopy, newly minted Ph.D. Ben Stuhl, Fellow Jun Ye, and a visiting…
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The Ye and Bohn groups have made a major advance in the quest to prepare “real-world” molecules at ultracold temperatures. As recently reported in Nature, graduate students Ben Stuhl and Mark Yeo, research associate Matt Hummon, and…
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The world’s most stable optical atomic clock resides in the Ye lab in the basement of JILA’s S-Wing. The strontium-(Sr-)lattice clock is so stable that its frequency measurements don’t vary by more than 1 part in 100 quadrillion (1 x 10^{-17…
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Researchers from a German national laboratory, the Physikalisch-Technische Bundesanstalt (PTB) have collaborated with Fellow Jun Ye, Visiting Fellow Lisheng Chen (Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences), and…
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The Ye group has created the world’s first “ruler of light” in the extreme ultraviolet (XUV). The new ruler is also known more formally as the XUV frequency comb. The comb consists of hundreds of equally spaced “colors” that function in precision…
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Physicists would very much like to understand the physics underlying high-temperature superconductors. Such an understanding may lead to the design of room temperature superconductors for use in highly efficient and much lower-cost transmission…
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The Ye group has built a cool new system for studying cold collisions between molecules. The system is far colder than a typical chemistry experiment that takes place at room temperature or hotter (300–500 K). But, it’s also much warmer than…
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In 2008, the Ye and Jin groups succeeded in making ultracold potassium-rubidium (KRb) molecules in their ground state (See “Redefining Chemistry at JILA” in the Spring 2010 issue of JILA Light & Matter). Their next goal was to figure out how…
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In 2008-2009, much to their amazement,researchers working on the Jun Ye group’s neutral Sr optical atomic clock discovered tiny frequency shifts caused by colliding fermions! They figured out that the clock laser was interacting slightly…
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“Nature is built quantum mechanically,” says Fellow Jun Ye, who wants to understand the connections between atoms and molecules in complex systems such as liquids and solids (aka condensed matter). He says that the whole Universe is made of…
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Fellow Jun Ye’s group has enhanced the molecular fingerprinting technique with the development of a mid-infrared (mid-IR) frequency comb.  The new rapid-detection technique can now identify traces of a wider variety of molecules found in mixtures…
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Fellows Deborah Jin, Jun Ye, and John Bohn are exploring new scientific territory in cold-molecule chemistry. Experimentalists Jin and Ye and their colleagues can now manipulate, observe, and control ultralow-temperature potassium-rubidium (KRb)…
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The cold-molecule collaboration has developed a method for directly imaging ultracold ground-state KRb molecules. Their old method required the transfer of ultracold KRb molecules into a Feshbach state, which is sensitive to electric and magnetic…
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According to the laws of quantum mechanics, identical fermions at very low temperatures can’t collide. These unfriendly subatomic particles, atoms, or molecules simply will not share the same piece of real estate with an identical twin. A few…
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In the summer of 2008, Fellow Jun Ye spent a couple of months at CalTech, where he ran into another visiting professor, former JILA Fellow Peter Zoller. Zoller left JILA in 1994 to become Professor of Physics at the University of Innsbruck (…
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To be the best they can be, optical atomic clocks need better clock lasers — lasers that remain phase coherent a hundred times longer than the very best conventional lasers. For instance, light from the clock laser in Fellow Jun Ye’s lab can…
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Last year the Ye group conducted an actual laboratory astrophysics experiment. Graduate students Brian Sawyer, Ben Stuhl, and Mark Yeo, research associate Dajun Wang, and Fellow Jun Ye fired cold hydroxyl (OH) radicals into a linear decelerator…
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Fellow Jun Ye’s group is methodically working its way toward the creation of an X-Ray frequency comb. Recently, senior research associate Thomas Schibli, graduate student Dylan Yost, Fellow Jun Ye, and colleagues from IMRA America, Inc. developed…
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By late 2006, Fellow Jun Ye’s clock team had raised the accuracy of its strontium (Sr)-lattice atomic clock to be just shy of that of the nation’s primary time and frequency standard, the NIST-F1 cesium (Cs) fountain clock. Graduate students…
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What sort of experiment could detect the effects of quantum gravity, if it exists? Theories that go beyond the Standard Model of physics include a concept that links quantum interactions with gravity. Physicists would very much like to find…
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With every breath you take, you breathe out carbon dioxide and roughly 1000 other different molecules. Some of these can signal the early onset of such diseases as asthma, cystic fibrosis, or cancer. Thanks to graduate student Mike Thorpe and his…
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When the Jin and Ye group collaboration wanted to investigate the creation of stable ultracold polar molecules, the researchers initially decided to make ultracold KRb (potassium-rubidium) molecules and then study their collision behavior. Making…
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Researchers from the Ye, Bohn, and Greene groups are busy exploring a cold new world crawling with polar hydroxyl radical (OH) molecules. The JILA experimentalists have already discovered how to cool OH to “lukewarm” temperatures of 30 mK. They’…
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In the race to develop the world's best optical atomic clock, accuracy and precision are what count. Accuracy is the degree to which a measurement of time conforms to time's true value. Precision is a gauge of the exactness, or reproducibility,…
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"In the right light, in the right time, everything is extraordinary," according to photographer Aaron Rose. He could have just as easily been describing precision optical spectroscopy experiments recently conducted by Research Associates Tanya…
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There's only one way to prove you've invented a better atomic clock: Come out on top of a comparison of your clock with one of the world's best atomic clocks: The NIST-F1 cesium fountain atomic clock, the nation's primary time and frequency…
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Science sleuths have a new and powerful method for identifying (and investigating) atoms and molecules, thanks to Graduate Student Mike Thorpe, Research Associate Kevin Moll, Senior Research Associate Jason Jones, Undergraduate Student Assistant…
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Scientists in Fellow Jun Ye's lab are developing a high-precision optical atomic clock linked to super-narrow optical transitions in ultracold, trapped strontium atoms. However, unless the new clock is portable (it is not) or researchers figure…
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Fellow Jan Hall has been working on stabilizing the frequency of lasers since the 1960s. Now, he, JILA Research Associate Mark Notcutt, Long-Sheng Ma (currently at BIPM in France), and Fellow Jun Ye have devised an improved, compact, and less…
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Jason Jones, Kevin Moll, Mike Thorpe, and Jun Ye have generated the world's first precise frequency comb in the extreme ultraviolet (EUV) using a combination of an ultrafast mode-locked laser and a precision high-finesse optical cavity. The EUV…
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A high-powered JILA collaboration led by JILA Fellows Jun Ye and Chris Greene is making important progress toward developing an ultrastable, high-accuracy optical atomic clock. The new optical clock design will use a variety of laser sources…
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Three years ago Jun Ye decided to apply an old idea for amplifying and stabilizing continuous-wave (cw) lasers to state-of-the-art ultrafast lasers. In 2002, Jason Jones, a postdoctoral fellow with Jun, analyzed whether the build-up cavities used…
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