News & Research Highlights

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.

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 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.

Members of the Jin group found a way to measure for the first time the a type of abstract “surface” in a gas of ultracold atoms that had been predicted in 1926 but not previously observed. Jin and her colleagues are leading researchers in the field of ultracold Fermi gases made up of thousands to millions of fermions.

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 graduate student Mike Martin to come up with a clever approach to reducing heat-related “noise” in interferometers. 

Fellow Cindy Regal,  recent JILA grad Matthew Squires (Anderson group, Ph.D. 2008),  former postdoc Wen Li (Kapteyn/Murnane group), and JILA grad Ian Coddington (Cornell group, Ph. D. 2004) have received prestigeous Presidential Early Career Awards for Scientists and Engineers, according to a White House press release issued July 23. Each award is for $1 million over 5 years.

Fellow Ana Maria Rey is Woman Physicist of the Month for June. Rey is  theorist working on many complicated problems in Atomic, Molecular, and Optical (AMO) Physics.  She is well known for her collaborations at JILA with experimentalists Deborah Jin and Jun Ye as well as theorist Murray Holland, CU theorists Victor Guarie and Michael Hermele, and physicists at institutions in the United States and abroad.

News Flash!  The Rey group has discovered another good reason for using alkaline-earth atoms, such as strontium (Sr) or Ytterbium (Yb), in experimental quantum simulators. Quantum simulators are systems that mimic interesting materials or mathematical models in a very controlled way. The new reason for using alkaline earth atoms in such systems comes from the fact that their nuclei come in as many as 10 different magnetic flavors, i.e., their spins can be in 10 different quantum states.

The Thompson group, with theory help from the Holland group, recently demonstrated a superradiant laser that escapes the “echo chamber” problem that limits the best lasers. To understand this problem, imagine an opera singer practicing in an echo chamber. The singer hears his own voice echo from the walls of the room. He constantly adjusts his pitch to match that of his echo from some time before. But, if the walls of the room vibrate, then the singer’s echo will be shifted in pitch after bouncing off of the walls. As a result, if the singer initially started singing an A, he may eventually end up singing a B flat, or a G sharp, or any other random note — spoiling a perfectly good night at the opera.

The Kapteyn/Murnane group and scientists from NIST Boulder and Germany have figured out how the interaction of an ultrafast laser with a metal alloy of iron and nickel destroys the metal’s magnetism. In a recent experiment, the researchers were able to observe how individual bits of quantum mechanical magnetization known as “spin” behaved after the metal was heated with the laser.

The Greene group has just discovered some weird quantum states of ultracold fermions that are also dipoles. Dipoles are particles with small positively and negatively charged ends. Atoms (or molecules) that are fermions cannot occupy the same quantum state — unlike the neighborly bosons that readily occupy the same state and form Bose-Einstein condensates at ultracold temperatures. The new theoretical study was interesting because it explored what would happen to dipolar fermions under the same conditions that cause dipolar bosons to form infinitely many three-atom molecules even though no two bosons ever form a molecule under these conditions!

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 measurement like the tics on an ordinary ruler. The amazing thing about this ruler is that XUV colors have such short wavelengths they aren’t even visible to the human eye. The wavelengths of the XUV colors range from about 120 nm to about 50 nm — far shorter than the shortest visible light at 400 nm. “Seeing” the colors in the XUV ruler requires special instruments in the laboratory. With these instruments, the new ruler is opening up whole new vistas of research.

Incredibly sensitive measurements can be made using particles that are correlated in a special way (called entanglement.)  Entanglement is one of the spooky properties of quantum mechanics – two particles interact and retain a connection, even if separated by huge distances.  If you do something to one of the particles, its linked partners will also respond.

We can get valuable information about a material by studying how it responds to light.  But up to now, researchers have been forced to ignore how some of light’s stranger quantum behavior, such as being in a superposition of one or more intensity states, affects these measurements.  New research from the Cundiff group (with newly minted PhD Ryan Smith and graduate student Andy Hunter) has shown that it is possible to back-calculate how a semiconductor responds to light’s quantum features even though we can’t directly create light with those features.

Theorists Norio Takemoto (now at the Weizmann Institute of Science) and Fellow Andreas Becker figured that something was amiss when they first analyzed the details of what occurs when an ultrafast laser dislodges an electron from a “simple” molecular ion, H₂⁺. Since H₂⁺ has already lost one of its electrons, its two protons only have one electron left to play with.  How hard would it be to “see” what happened to this electron in a strong laser field? After all, a widely accepted theory said that a strong laser field would make it easier for the lone electron to escape when the ion was stretched apart (as opposed to contracted). 

Graduate student Jennifer Lubbeck (Jimenez Group) spent the summer of 2011 doing research in the Molecular Spectroscopy Laboratory at the RIKEN Institute in Wako, Japan (near Tokyo). Her host's group included 16 postdocs and four graduate students. The group was under the direction of Chief Scientist Tahei Tahara. However, Lubbeck actually worked directly with just five other young scientists under the supervision of Professor Kunihiko Ishi (Ishi-san).

The Nesbitt group wants to figure out how chemistry works in outer space. In particular, the group wants to understand the “cosmo”-chemistry leading to the generation of soot, which is similar to products of combustion here on Earth.

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 networks for electricity. A technological breakthrough like this would drastically reduce world energy costs. However, this breakthrough requires a detailed understanding of the physics of high-temperature superconductivity.

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 experiments that investigate ultracold-molecule collisions conducted at hundreds of billionths of a degree above absolute zero (0 K). The new system is known as “the cold molecule experiment” and operates at temperatures of approximately 5 K (-450 °F).

JILA’s quest to determine whether the electron has an electric dipole moment (eEDM) began in 2006 with a suggestion by Fellow Eric Cornell that the molecular ion hafnium fluoride (HfF⁺) might be well suited for an eEDM experiment. An electric dipole moment is a measure of the separation of positive and negative charges in a system. If an electron does have an electric dipole moment, it’s a pretty darn small one. So small, in fact, that if the electron were the size of the Earth, its eEDM would only alter the planet’s roundness by less than the width of a human hair.