atomic physics

In this episode of Relatively Certain, Dina Genkina sits down with JQI Adjunct Fellow Marianna Safronova, a physics professor at the University of Delaware, and JQI Fellow Charles Clark, an adjunct professor of physics at UMD and a fellow of the National Institute of Standards and Technology, to talk about how precision measurements with atoms might shed some light on matter that’s otherwise dark.

Scientists at the Joint Quantum Institute (JQI) have observed, for the first time, interference between particles of light created using a trapped ion and a collection of neutral atoms. Their results could be an essential step toward the realization of a distributed network of quantum computers capable of processing information in novel ways.

Electrons inside an atom whip around the nucleus like satellites around the Earth, occupying orbits determined by quantum physics. Light can boost an electron to a different, more energetic orbit, but that high doesn’t last forever. At some point the excited electron will relax back to its original orbit, causing the atom to spontaneously emit light that scientists call fluorescence. Scientists can play tricks with an atom’s surroundings to tweak the relaxation time for high-flying electrons, which then dictates the rate of fluorescence. In a new study, researchers at the Joint Quantum Institute observed that a tiny thread of glass, called an optical nanofiber, had a significant impact on how fast a rubidium atom releases light. The research, which appeared as an Editor’s Suggestion in Physical Review A, showed that the fluorescence depended on the shape of light used to excite the atoms when they were near the nanofiber.

Large-scale quantum computers, which are an active pursuit of many university labs and tech giants, remain years away. But that hasn’t stopped some scientists from thinking ahead, to a time when quantum computers might be linked together in a network or a single quantum computer might be split up across many interconnected nodes.A group of physicists at the University of Maryland, working with JQI Fellow Christopher Monroe, are pursuing the second goal, attempting to wire up isolated modules of trapped atomic ions with light. They imagine many modules, each with a hundred or so ions, linked together to form a quantum computer that is inherently scalable: If you want a bigger computer, simply add more modules to the mix.In a paper published recently in Physical Review Letters, Monroe and his collaborators reported on putting together many of the pieces needed to create such a module. It includes two different species of ions: an ytterbium ion for storing information and a barium ion for generating the light that communicates with other nodes.This dual-species approach isolates the storage and communication tasks of a network node. With a single species, manipulating the communication ion with a laser could easily corrupt the storage ion. In several experiments, the researchers demonstrated that they could successfully isolate the two ions from each other, transfer information between them and capture light generated by both ions. 

The behavior of a few rubidium atoms in a cloud of 40,000 hardly seems important. But a handful of the tiny particles with the wrong energy may cause a cascade of effects that could impact future quantum computers. Some proposals for quantum devices use Rydberg atoms—atoms with highly excited electrons that roam far from the nucleus—because they interact strongly with each other and offer easy handles for controlling their individual and collective behavior. Rubidium is one of the most popular elements for experimenting with Rydberg physics. Now, a team of researchers led by JQI Fellows Trey Porto, Steven Rolston and Alexey Gorshkov have discovered an unwanted side effect of trying to manipulate strongly interacting rubidium atoms: When they used lasers to drive some of the atoms into Rydberg states, they excited a much larger fraction than expected. The creation of too many of these high-energy atoms may result from overlooked “contaminant” states and could be problematic for proposals that rely on the controlled manipulation of Rydberg atoms to create quantum computers.

Strongly correlated electronic systems, like superconductors, display remarkable electronic and magnetic properties, and are of considerable research interest. These systems are fermionic, meaning they are composed of a class of particle called a fermion. Bosonic systems, composed another family of particles called bosons, offer a level of control often not possible in solid state systems. Creating analogous states in bose gases is an excellent way to model the dynamics of these less tractable systems. This means engineering a gas that, when cooled down to a condensate, assumes a phase equivalent to its solid state counterpart.
JQI theorists Juraj Radic, Stefan Natu, and Victor Galitski have proposed a new magnetic phase for a bose gas. The transition to this phase is analogous to the formation of ferromagnetism in magnetic materials, like iron, and might give insight into the physics of...

Phil Schewe discusses quantized energy levels with Steve Rolston (JQI) and Wes Campbell (former JQI postdoc and current UCLA professor). The concept of electronic energy levels in an atom has applications everywhere, from sodium lamps to brake lights to quantum information and atomic clocks.