Research Highlights

New theory describing the spin behavior of ultracold polar molecules is opening the door to explorations of exciting, new physics in JILA’s cold molecular lab, operated by the Jin and Ye groups. According to the Rey theory group and its collaborators, ultracold dipolar molecules can do even more interesting things than swapping spins.

Dynamical phase transitions in the quantum world are wildly noisy and chaotic. They don’t look anything like the phase transitions we observe in our everyday world. In Colorado, we see phase transitions caused by temperature changes all the time: snow banks melting in the spring, water boiling on the stove, slick spots on the sidewalk after the first freeze. Quantum phase transitions happen, too, but not because of temperature changes. Instead, they occur as a kind of quantum “metamorphosis” when a system at zero temperature shifts between completely distinct forms.

A Be star is a luminous, blue B-type star with distinctive spectral lines that can provide two types of feasts (tasty snacks or full-scale banquets) for a former companion star in a binary system. The feasting begins when the companion star goes supernova and becomes a neutron star or, more rarely, a black hole. Typically, the companion blows up with enough force to kick itself into an eccentric (elliptical) orbit that is misaligned with respect to the Be star’s orbit.

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 observed a manifestation of SU(N≤10) symmetry in the magnetic behavior of strontium-87 (⁸⁷Sr) atoms trapped in crystals of light created by intersecting laser beams inside a quantum simulator (originally developed as an optical atomic clock).

The Raschke group recently came up with a clever way to detect folds and grain boundaries in graphene. a sheet made of a single layer of carbon atoms.Such defects stop the flow of electrons in graphene and are a big headache for engineers working on touch screens and other electronic devices made of this material.

The spooky quantum property of entanglement is set to become a powerful tool in precision measurement, thanks to researchers in the Thompson group. Entanglement means that the quantum states of something physical—two atoms, two hundred atoms, or two million atoms—interact and retain a connection, even over long distances.

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 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 extraordinarily long phase-coherence time. This feat is so profound, it is nearly certain to transform the investigation of matter with extreme ultraviolet light, according to Ye’s colleagues in precision measurement and laser science. This research was reported online in Nature Photonics this week.

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 delivering the most precise timekeeping in all of human history—to every member nation regardless of politics, alliances, or behavior on the ground. Moreover, the world clock itself is virtually immune to sabotage and can peer under the surface of the Earth to uncover its detailed composition or out into space to reveal a better understanding of fundamental physical principles such as quantum mechanics and gravity. 

Mid-infrared (mid-IR) laser light is accomplishing some remarkable things at JILA. This relatively long-wavelength light (2–4 µm), when used to drive a process called high-harmonic generation, can produce bright beams of soft x-rays with all their punch packed into isolated ultrashort bursts. And, all this takes place in a tabletop-size apparatus. The soft x-rays bursts have pulse durations measured in tens to hundreds of attoseconds (10^-18 s).

Biomolecules may not always behave the same way in test tubes as they do in living cells, a fact underscored by important new work by former research associate Nick Dupuis, graduate student Erik Holmstrom, and Fellow David Nesbitt. The researchers found that under crowded conditions that begin to mimic those found in cells, single RNA molecules folded 35 times faster than in the dilute solutions typically used in test-tube experiments.

The Markus Raschke group has come up with an innovative way that may one day allow it to peer inside superconductors, new materials for solar cells, or even a single cell and identify the inner workings of these complex systems. The new method is able to determine where the different chemical constituents are located and how their spatial distribution determines their function.

Fellow Tom Perkins’ group is significantly closer to realizing its long-standing dream of using atomic force microscopy (AFM) to study how membrane proteins fold and unfold. Historically, scientists have used AFM to measure the mechanical forces needed to unfold individual proteins and the resulting increase in their lengths. However, the limitations of AFM itself have prevented researchers from watching the unfolding process in detail.

Graduate student Erik Holmstrom and Fellow David Nesbitt have applied their laboratory research on the rates of RNA folding and unfolding to the medically important enzyme telomerase. Telomerase employs both protein and RNA components to lengthen chromosomes, which are shortened every time they are copied.

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.

Quantum chaos just showed up in an ultracold gas of erbium atoms, and the Bohn theory group knows why. Theorists expect quantum chaos to appear when quantum mechanical objects get sufficiently complicated. But until now, scientists hadn’t realized that something as simple as a pair of colliding atoms could be complicated enough for quantum chaos to appear.

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) molecules in the KRb quantum simulator. The main reason the molecules do not collide and react is continuous measurement of molecule loss from the simulator.

When Andy Almand-Hunter and his colleagues in the Cundiff group shined a laser on a sample of gallium arsenide (GaAs), the last thing they were expecting to create was a fog of liquid-like quantum droplets, which the group named "dropletons." Dropletons are a new, stable form of matter much like an ordinary liquid—with one key difference.

The groups of Fellow Adjoint Markus Raschke and Fellow Tom Perkins joined forces recently to shine light onto a bacterial membrane protein called bacteriorhodopsin (bR). They used a new infrared (IR) light imaging system with a spatial resolution and chemical sensitivity of just a few bR molecules. In their experiment, the tip of an atomic force microscope (AFM) acted like an antenna for the IR light, focusing it onto the sample.

Fellows Mitch Begelman and Phil Armitage have just solved the 40-year old mystery of what causes the gas of stellar debris surrounding black holes in binaries to flip back and forth cyclically between a spherical cloud and a luminous disk.