Research Highlights

When atoms collide, their exact structure—for example, the number of electrons they have or even the quantum spin of their nuclei—has a lot to say about how they bounce off each other. This is especially true for atoms cooled to near-zero Kelvin, where quantum mechanical effects give rise to unexpected phenomena.  Collisions of these cold atoms can sometimes be caused by incoming laser light, resulting in the colliding atom-pair forming a short-lived molecular state before disassociating and releasing an enormous amount of energy. These so-called light-assisted collisions, which can happen very quickly, impact a broad range of quantum science applications, yet many details of the underlying mechanisms are not well understood. 

In a new study published in Physical Review Letters, JILA Fellow and University of Colorado Boulder physics professor Cindy Regal, along with former JILA Associate Fellow Jose D’Incao (currently an assistant professor of physics at the University of Massachusetts, Boston) and their teams developed new experimental and theoretical techniques for studying the rates at which light-assisted collisions occur in the presence of small atomic energy splittings.  Their results rely upon optical tweezers—focused lasers capable of trapping individual atoms—that the team used to isolate and study the products of individual pairs of atoms.

Researchers at the University of Colorado Boulder have developed a novel method to measure magnetic field orientations using atoms as minuscule compasses. The research, a collaboration between JILA Fellow and CU Boulder physics professor Cindy Regal and Svenja Knappe, a research professor in the Paul M. Rady Department of Mechanical Engineering, was recently published as the cover article in the journal Optica.

When measuring minor changes for quantities like forces, magnetic fields, masses of small particles, or even gravitational waves, physicists use micro-mechanical resonators, which act like tuning forks, resonating at specific frequencies. Traditionally, it was assumed that the temperature across these devices is uniform. 

However, new research from JILA Fellow and University of Colorado Boulder physics professor Cindy Regal and her team, Dr. Ravid Shaniv and graduate student Chris Reetz has found that in specific scenarios, such as advanced studies looking at the interactions between light and mechanical objects, where the temperature might differ in various resonator parts, which lead to unexpected behaviors. Their observations, published in Physical Review Research, can potentially revolutionize the design of micro-mechanical resonators for quantum technology and precision sensing.

When it comes to creating ever more intriguing quantum systems, a constant need is finding new ways to observe them in a wide range of physical scenarios.  JILA Fellow Cindy Regal and JILA and NIST Fellow Ana Maria Rey have teamed up with Oriol Romero-Isart, a professor at the University of Innsbruck and IQOQI (Institute for Quantum Optics and Quantum Information) to show that a trapped particle in the form of an atom readily reveals its full quantum state with quite simple ingredients, opening up opportunities for studies of the quantum state of ever larger particles.

JILA Fellow Cindy Regal and her team, along with researchers at the National Institute of Standards and Technology (NIST), have for the first time demonstrated that they can trap single atoms using a novel miniaturized version of “optical tweezers” — a system that grabs atoms using a laser beam as chopsticks.

More than 400 years later, scientists are in the midst of an equally-important revolution. They’re diving into a previously-hidden realm—far wilder than anything van Leeuwenhoek, known as the “father of microbiology,” could have imagined. Some researchers, like physicists Margaret Murnane and Henry Kapteyn, are exploring this world of even tinier things with microscopes that are many times more precise than the Dutch scientist’s. Others, like Jun Ye, are using lasers to cool clouds of atoms to just a millionth of a degree above absolute zero with the goal of collecting better measurements of natural phenomena. 

The process of developing a quantum computer has seen significant progress in the past 20 years. Quantum computers are designed to solve complex problems using the intricacies of quantum mechanics. These computers can also communicate with each other by using entangled photons (photons that have connected quantum states). As a result of this entanglement, quantum communication can provide a more secure form of communication, and has been seen as a promising method for the future of a more private and faster internet.

Qubits are a basic building block for quantum computers, but they’re also notoriously fragile—tricky to observe without erasing their information in the process. Now, new research from CU Boulder and the National Institute of Standards and Technology (NIST) may be a leap forward for handling qubits with a light touch.  

In the study, a team of physicists demonstrated that it could read out the signals from a type of qubit called a superconducting qubit using laser light—and without destroying the qubit at the same time.

Artist's depiction of an electro-optic transducer, an ultra-thin wafer that can read out the information from a superconducting qubit.

Artist's depiction of an electro-optic transducer, an ultra-thin device that can capture and transform the signals coming from a superconducting qubit. (Credit: Steven Burrows/JILA)

The group’s results could be a major step toward building a quantum internet, the researchers say. Such a network would link up dozens or even hundreds of quantum chips, allowing engineers to solve problems that are beyond the reach of even the fastest supercomputers around today. They could also, theoretically, use a similar set of tools to send unbreakable codes over long distances. 

The study, published June 15 in the journal Nature, was led by JILA, a joint research institute between CU Boulder and NIST.

JILA Fellow Cindy Regal has helped consult on a new mural placed in Washington Park in Denver, Colorado. The mural, titled Leading Light, loosely alludes to AMO physics, which Regal studies by using laser beams. With bright yellows and vivid pinks, the mural depicts four women interacting with different blue spheres, representing electrons. One woman wears sunglasses, modeled on thelaser goggles that JILAns wear for lab safety. The artist, Amanda Phingbodhipakkiya, found Regal's work captivating. “We share a vision to not only uplift women in STEM and to bring science and our society closer together, but also to foster dynamic and organic relationships with science in everyone, whether or not they choose to become scientists,” the artist said.

Trapping single atoms is a bit like herding cats, which makes researchers at the University of Colorado Boulder expert feline wranglers. In a new study, a team led by physicist Cindy Regal showed that it could load groups of individual atoms into large grids with an efficiency unmatched by existing methods.  

Quantum computers are set to revolutionize society. With their expansive power and speed, quantum computers could reduce today’s impossibly complex problems, like artificial intelligence and weather forecasts, to mere algorithms. But as revolutionary as the quantum computer will be, its promises will be stifled without the right connections. Peter Burns, a JILA graduate student in the Lehnert/Regal lab, likens this stifle to a world without Wi-Fi.  

The Regal group recently met the challenge of measurements in an extreme situation with a device called an interferometer. The researchers succeeded by using creative alterations to the device itself and quantum correlations. Quantum correlations are unique, and often counterintuitive, quantum mechanical interactions that occur among quantum objects such as photons and atoms. The group exploited these interactions in the way they set up their interferometer, and improved its ability to measure tiny motions using photons (particles of light).

Bob Peterson and his colleagues in the Lehnert-Regal lab recently set out to try something that had never been done before: use laser cooling to systematically reduce the temperature of a tiny drum made of silicon nitride as low as allowed by the laws of quantum mechanics. Although laser cooling has become commonplace for atoms, researchers have only recently used lasers to cool tiny silicon nitride drums, stretched over a silicon frame, to their quantum ground state. Peterson and his team decided to see just how cold their drum could get via laser cooling.

The Regal and Rey groups have come up with a novel way to generate and propagate quantum entanglement [1], a key feature required for quantum computing. Quantum computing requires that bits of information called qubits be moved from one location to another, be available to interact in prescribed ways, and then be isolated for storage or subsequent interactions. The group showed that single neutral atoms carried in tiny traps called optical tweezers may be a promising technology for the job!

Graduate student Brian Lester of the Regal group has taken an important step toward building larger, more complex systems from single-atom building blocks. His accomplishment opens the door to advances in neutral-atom quantum computing, investigations of the interplay of spin and motion as well as the synthesis of novel single molecules from different atoms.

Graduate student Adam Kaufman and his colleagues in the Regal and Rey groups have demonstrated a key first step in assembling quantum matter one atom at a time. Kaufman accomplished this feat by laser-cooling two atoms of rubidium (⁸⁷Rb) trapped in separate laser beam traps called optical tweezers. Then, while maintaining complete control over the atoms to be sure they were identical in every way, he moved the optical tweezers closer and closer until they were about 600 nm apart. At this distance, the trapped atoms were close enough to “tunnel” their way over to the other laser beam trap if they were so inclined.

The Regal-Lehnert collaboration has just taken a significant step towards the goal of one day building a quantum information network. Large-scale fiber-optic networks capable of preserving fragile quantum states (which encode information) will be necessary to realize the benefits of superfast quantum computing.

Research associate Tom Purdy and his colleagues in the Regal group have just built an even better miniature light-powered machine that can now strip away noise from a laser beam. Their secret: a creative workaround of a quantum limit imposed by the Heisenberg Uncertainty Principle. This limit makes it impossible to simultaneously reduce the noise on both the amplitude and phase of light inside interferometers and other high-tech instruments that detect miniscule position changes.

Researchers in the Regal group have gotten so good at using laser light to track the exact position of a tiny drum that they have been able to observe a limit imposed by the laws of quantum mechanics. In a recent experiment, research associate Tom Purdy, graduate student Robert Peterson, and Fellow Cindy Regal were able to measure the motion of the drum by sending light back and forth through it many times. During the measurement, however, 100 million photons from the laser beam struck the drum at random and made it vibrate. This extra vibration obscured the motion of the drum at exactly the level of precision predicted by the laws of quantum mechanics.

The Regal group recently completed a nifty feat that had never been done before: The researchers grabbed onto a single trapped rubidium atom (⁸⁷Rb) and placed it in its quantum ground state. This experiment has identified an important source of cold atoms that can be arbitrarily manipulated for investigations of quantum simulations and quantum logic gates in future high-speed computers.