Research Highlights

When research associate Wei Xiong and graduate student Dan Hickstein studied quantum dots by shining laser light on them in the gas phase, they got some surprising results. The tiny chunks of material responded differently to series of two laser pulses — depending on their size. Scientists already knew that most of their quantum dots would end up with at least part of an electron wandering around outside of them for some period of time. However, Xiong and his colleagues showed that the electrons from the smallest quantum dots traveled the farthest away.

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 colleague Yong Xia (East China Normal University) have built a magneto-optical trap (MOT) for yttrium oxide (YO) molecules. The two-dimensional MOT uses three lasers and carefully adjusted magnetic fields to partially confine, concentrate, and cool the YO molecules to transverse temperatures of ~2 mK. It is the first device of its kind to successfully laser cool and confine ordinary molecules found in nature.

The Lehnert group has come up with a clever way to transport and store quantum information. Research associate Tauno Palomaki, graduate student Jennifer Harlow, NIST colleagues Jon Teufel and Ray Simmonds, and Fellow Konrad Lehnert have encoded a quantum state onto an electric circuit and figured out how to transport the information from the circuit into a tiny mechanical drum, where is stored. Palomaki and his colleagues can retrieve the information by reconverting it into an electrical signal.

Astrophysicist Fellow Jeff Linsky and his colleagues from CU’s Center for Astrophysics and Space Astronomy have come up with a neat strategy for helping to determine whether an exoplanet’s atmosphere contains evidence of Earth-like life. The first step is to see whether an exoplanet’s atmosphere contains oxygen (O₂), ozone (O₃), or other molecules that could have been produced by Earth-like organisms such as the plants that produce O₂. Next, Linsky and his collaborators propose analyzing spectral lines from the host star’s light to determine if the same molecules could exist in the atmosphere without life.

Fellow Mitch Begelman and colleague Marek Sikora of the Polish Academy of Sciences have proposed a solution for the long-standing puzzle of what causes black holes to launch powerful jets. Jets are extremely energetic material (plasma) traveling at very close to the speed of light and spanning distances of thousands to hundreds of thousands of light years.

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.

Ana Maria Rey’s group is devising new theoretical methods to help experimentalists use ultracold atoms, ions, and molecules to model quantum magnetism in solids. Research associate Kaden Hazzard, former research associate Salvatore Manmana, newly minted Ph.D. Michael Foss-Feig, and Fellow Rey are working on developing new tools to understand these models, which describe both solids and ultracold particles. The theorists are collaborating with three experimental teams at JILA and the National Institute of Standards and Technology (NIST).

When experimental physicists at Penn State were unable to observe some of the predicted behaviors of ultracold rubidium (Rb) atoms expanding inside a two-dimensional crystal of light, they turned to their theorist colleagues at the City University of New York and JILA for an explanation. Graduate student Shuming Li and Fellow Ana Maria Rey were happy to oblige.

The Cundiff group has taken an important step forward in the study of the quantum world. It has come up with an experimental technique to measure key parameters needed to solve the Schrödinger equation. The amazing Schrödinger equation describes the time-dependent evolution of quantum states in a physical system such as the group’s hot gas of potassium atoms (K). But, for the equation to work, someone has to figure out a key part of the equation known as the Hamiltonian.

Gold glitters because it is highly reflective, a quality once considered important for precision measurements made with gold-coated probes in atomic force microscopy (AFM). In reality, the usual gold coating on AFM probes is a major cause of force instability and measurement imprecision, according to research done by the Perkins group.

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 Fellow Jun Ye succeeded in cooling hydroxyl radical molecules (^*OH) down to temperatures of no more than five thousandths of a degree above absolute zero (5mK).

When the Thompson group first demonstrated its innovative “superradiant” laser the team noticed that sometimes the amount of light emitted by the laser would fluctuate up and down.  The researchers wondered what was causing these fluctuations. They were especially concerned that whatever it was could also be a problem in future lasers based on the same principles.

The Nesbitt group has figured out the central role of “plasmon resonances” in light-induced emission of electrons from gold or silver nanoparticles. Plasmons are rapid-fire electron oscillations of freely moving (conduction) electrons in metals. They are caused by light of just the “right frequency.”

Graduate student Ben Knurr and Fellow Mathias Weber have added new insight into a catalytic reaction based on a single gold atom with an extra electron that transfers this electron into carbon dioxide molecules (CO₂). This reaction could be an important first step future industrial processes converting waste CO₂ back into chemical fuels. As such, it could play a key role in a future carbon-neutral fuel cycle.

Most scientists think it is really hard to correlate, or entangle, the quantum spin states of many particles in an ultracold gas of fermions. Fermions are particles like electrons (and some atoms and molecules) whose quantum spin states prevent them from occupying the same lowest-energy state and forming a Bose-Einstein condensate. Entanglement means that two or more particles interact and retain a connection. Once particles are entangled, if something changes in one of them, all linked partners respond.

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) over a time period of 1000 seconds, or 17 minutes.

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.

The Jin and Cornell groups have discovered irrefutable evidence for the contact. The contact appears in ultracold gases under conditions when the atoms are close “contact” in a Bose-Einstein condensate, or BEC.  Like pressure, volume, and temperature, the contact is an important property of ultracold ensembles of atoms.  The contact is particularly important when the atoms interact with each other, since the contact tells you how likely it is that an atom in the ensemble is having a close encounter with another atom.

Former research associate Antonio Picón, research associate Agnieszka Jaron-Becker, and Fellow Andreas Becker have discovered a way to make the hydrogen molecular ion (H₂⁺) fall apart into its constituent atoms without exciting or ionizing the electron. This startling finding was a big surprise for the researchers, who recently figured out how to do something that conventional wisdom said was difficult, if not downright impossible.

Research associate Bruno Giacomazzo recently studied the effects of magnetic fields and matter on the likelihood that the merger of two black holes will produce jets of light of different frequencies ranging from radio waves to X-rays. If such signals are generated, it may be possible to detect them with ground- or space-based observatories. Their detection would help astronomers identify and study the unions of supermassive black holes that occur after galaxies collide. Supermassive black holes are found at the centers of most galaxies in the Universe.