Research Highlights

Precision Measurement | Quantum Information Science & Technology
A Magic Balance in Optical Lattice Clocks
Local interactions in the same lattice pull clock frequency negative while interactions between atoms on neighboring lattice sites pull clock frequency positive. By adjusting the atomic confinement, or tightness, of the lattice, researchers can balance these two counteracting forces to increase clock sensitivity.
Published: October 12, 2022

Atomic clocks are essential in building a precise time standard for the world, which is a big focus for researchers at JILA. JILA and NIST Fellow Jun Ye, in particular, has studied atomic clocks for two decades, looking into ways to increase their sensitivity and accuracy. In a new paper published in Science Advances, Ye and his team collaborated with JILA and NIST Fellow Ana Maria Rey and her team to engineer a new design of clock, which demonstrated better theoretical understanding and experimental control of atomic interactions, leading to a breakthrough in the precision achievable in state-of-the-art optical atomic clocks.

PI: Ana Maria Rey | PI: Jun Ye
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Quantum Information Science & Technology
Clearing Quantum Traffic Jams under the SU(n) of Symmetric Collisions
An artistic rendering of the two planes of the atom's movement, with the real being a 1D lattice and the synthetic referring to the nuclear spin of the atom
Published: September 15, 2022

Of all the atoms that quantum physicists study, alkaline atoms hold a special place due to their unique structure. Found in the second column of the periodic table, these atoms have two outer electrons, allowing the atoms to interact with one another in intriguing ways. “They have received a lot of attention in recent years among the physics community because of two reasons,” explained JILA and NIST Fellow Ana Maria Rey. “One is that they have a unique atomic structure, which makes them ideal for atomic clocks. This is because they have a long-lived electronic excited state that can live longer than 100 seconds. The second is that their electronic and nuclear spin degrees of freedom are highly decoupled and therefore the nuclear spins do not participate in the atomic collisions.”

Like planets orbiting the sun while rotating, an atom's electrons orbit the nucleus while spinning. The nucleus itself also spins, and this spin can be linked, or “coupled” to the electrons' spins. If the nuclear spin is coupled, it (indirectly) participates in collisions with other atoms. If it is not coupled (decoupled), the nuclear spin is uninvolved in these collisions. For decoupled nuclei, their properties give rise to a unique symmetry called SU(n) symmetry, where the strength of the interactions between the atoms is uninfluenced by what nuclear spins are involved in the collisions. “Here n corresponds to the number of nuclear spin states,” Rey added. “In an alkaline earth atom like strontium, it can be up to 10.” In a new paper published in PRX Quantum, Rey and her team of researchers proposed a new method for seeing the quantum effects enabled by SU(n) symmetry in current experimental conditions, something that has been historically challenging for physicists.

PI: Ana Maria Rey
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Quantum Information Science & Technology
A Look at Colorado's Quantum Revolution
Child wears a helmet made up of more than 100 OPM sensors.
Published: June 28, 2022

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. 

PI: Jun Ye | PI: Cindy Regal | PI: Margaret Murnane | PI: Henry Kapteyn | PI: Ana Maria Rey
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Precision Measurement | Quantum Information Science & Technology
An Atomic Game of Duck, Duck, Goose
Selected atoms (green) within doubly occupied sites of a 2D "Fermi Sea" are excited by a polarized laser pulse. Pauli blocking prevents decay of the excited atoms (red) as they can only decay into unoccupied sites (black).
Published: April 15, 2022

Physics has always been a science of rules. In many situations, these rules lead to clear and simple theoretical predictions which, nevertheless, are hard to observe in actual experimental settings where other confounding effects may obscure the desired phenomena. For JILA and NIST Fellows Ana Maria Rey and Jun Ye, one type of phenomena they are especially interested in observing are the interactions between light and atoms, especially those at the heart of the decay of an atom prepared in the excited state. “If you have an atom in the excited state, the atom will eventually decay to the ground state while emitting a photon,” explained Rey. “This process is called spontaneous emission.” The spontaneous emission rate can be manipulated by scientists, making it longer or shorter, depending on the experimental conditions. Many years ago it was predicted that one way to suppress or slow down spontaneous emission was by applying a special type of statistics known as Fermi statistics which prevents two identical fermions from being in the same quantum state, known as the Pauli Exclusion Principle

This principle is similar to a game of Duck, Duck, Goose, where two individuals fight over an open spot in a circle in order to avoid being “it.” Like children in this game, the atoms must find an empty quantum state to decay into. If they cannot find an empty state, interesting things begin to happen. “If an excited atom wants to decay, but the ground state is already filled, then the decay is “Pauli blocked” and the atom will stay in the excited state longer, or even forever,” Rey said. Nevertheless, the experimental observation of this effect happened to be challenging.  It was not until last year  that the Ye group observed Pauli blocking of radiation for the first time indirectly by measuring the light scattered by the atoms—but a direct observation of Pauli blocking by measuring  the lifetime of atoms in the steady state was lacking. More recently, Ye’s and Rey’s groups collaborated in a joint study, and were able to find an appropriate experimental setting where they were able to observe Pauli blocking of spontaneous emission by direct measurements of the excited state population. The results have been published in the journal Physical Review Letters. 

PI: Jun Ye | PI: Ana Maria Rey
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Quantum Information Science & Technology
JILA and Cubit Partner with Key Quantum Companies for an Engaging Panel
Panelists from left to right: Ana Maria Rey (JILA and NIST), Judith Olson (ColdQuanta), Johanna Zultak (Maybell Quantum), Star Fassler (Vescent), Sara Campbell (Quantinuum), and moderator Brittany Mazin (ColdQuanta)
Published: April 12, 2022

Colorado has a reputation for being a quantum ecosystem hotspot and a recent panel discussion further bolstered this image. It was hosted by JILA, a world-leading physics institute created by a partnership between the University of Colorado Boulder and NIST; and the CUbit Quantum Initiative, a CU Boulder research center. The panel, titled "Women in Quantum: What Does It Take," brought in individuals from both quantum research and the quantum industry. With panelists from some of the biggest names in the quantum industry, including ColdQuanta, Maybell Quantum, Quantinuum, and Vescent, the discussions about the industry itself were relevant and engaging.

PI: Ana Maria Rey
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Atomic & Molecular Physics | Precision Measurement | Quantum Information Science & Technology
Running in a Quantum Corn Maze and Getting Stuck in the Dark
Comparison of 2-level and 6-level atom decay paths. For 6-level systems, each state can potentially decay into several states and some of them might be dark due to destructive interference.
Published: March 23, 2022

Light is emitted when an atom decays from an excited state to a lower energy ground state, with the emitted photon carrying away the energy.  The spontaneous emission of light is a fundamental process that originates from the interaction between matter and the  modes of the electromagnetic field—the background “hiss” of the universe that is all around us. However, spontaneous emission of light can limit the utility of atomic excited states for a wide array of scientific and technological applications, from probing the nature of the universe to inertial navigation. Understanding ways to alter or even engineer spontaneous emission has been an intriguing topic in science.  JILA Fellows Ana Maria Rey and James Thompson study ways to control light emission by placing atoms in an optical cavity, a resonator made of two mirrors between which light can bounce back and forth many times. Together, with JILA postdoc and first author Asier Piñeiro Orioli, they have predicted that when an array of multi-level atoms is placed in the cavity the atoms can all cooperate and collectively suppress their emission of light into the cavity. These findings were recently published in Physical Review X.

PI: Ana Maria Rey | PI: James Thompson
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Precision Measurement | Quantum Information Science & Technology
Electrifying Molecular Interactions
A depiction showing the interaction between ultra cold compressed 2D gas layers of KRb molecules
Published: March 17, 2022

Worldwide, many researchers are interested in controlling atomic and molecular interactions. This includes JILA and NIST fellows Jun Ye and Ana Maria Rey, both of whom have spent years researching interacting potassium-rubidium (KRb) molecules, which were originally created in a collaboration between Ye and the late Deborah Jin. In the newest collaboration between the experimental (Ye) and theory (Rey) groups, the researchers have developed a new way to control two-dimensional gaseous layers of molecules, publishing their exciting new results in the journal Science.

PI: Jun Ye | PI: Ana Maria Rey
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Atomic & Molecular Physics | Quantum Information Science & Technology
A Magic Recipe for a Quantum Interferometer
A comparison of two optical cavities, with the left cavity having only localized atoms and no squeezing. In contrast, the right cavity depicts delocalized atoms, squeezing and entanglement.
Published: November 17, 2021

Gravimetry, or the measurement of the strength of a gravitational field (or gravitational acceleration), has been of great interest to physicists since the 1600s. One of the most precise ways to measure gravitational acceleration is to use an atom interferometer. There are many different types of atom interferometers but so far all operate using uncorrelated atoms that are not entangled. To build the best one allowed in nature, it requires harnessing the power of quantum entanglement. However, making a quantum interferometer with entangled atoms is challenging. JILA Fellows Ana Maria Rey and James K. Thompson have published a paper in Physical Review Letters that discusses a new protocol that could make entangled quantum interferometers easier to produce and use.

PI: Ana Maria Rey | PI: James Thompson
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Quantum Information Science & Technology
NIST’s Quantum Crystal Could Be a New Dark Matter Sensor
Illustration of a quantum crystal
Published: August 06, 2021

Physicists at the National Institute of Standards and Technology (NIST) have linked together, or “entangled,” the mechanical motion and electronic properties of a tiny blue crystal, giving it a quantum edge in measuring electric fields with record sensitivity that may enhance understanding of the universe.

PI: Ana Maria Rey
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Laser Physics | Quantum Information Science & Technology
BCS: Building a Cavity Superconductor
Model of an optical cavity
Published: May 18, 2021

The idea of quantum simulation has only become more widely researched in the past few decades. Quantum simulators allow for the study of a quantum system that would be difficult to study easily and quickly in a laboratory or model with a supercomputer. A new paper published in Physical Review Letters, by a collaboration between theorists in the Rey Group and experimentalists in the Thompson laborator,y proposes a way to engineer a quantum simulator of superconductivity that can measure phenomena so far inaccessible in real materials. 

PI: Ana Maria Rey | PI: James Thompson
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Quantum Information Science & Technology
Molecules in Flat Lands: an Entanglement Paradise
Model of the quantum gas pancake
Published: March 18, 2021

Entangled particles have always fascinated physicists, as measuring one entangled particle can result in  a change in another entangled particle, famously dismissed as “spooky action at a distance” by Einstein. By now, physicists understand this strange effect and how to make use of it, for example to increase the sensitivity of measurements. However, entangled states are very fragile, as they can be easily disrupted by decoherence. Researchers have already created entangled states in atoms, photons, electrons and ions, but only recently have studies begun to explore  entanglement in gases of polar molecules. 

PI: Ana Maria Rey | PI: Jun Ye
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Atomic & Molecular Physics
Total Ellipse of the SU(N)
SU(N) fermions display unique properties.
Published: September 11, 2020

A strangely shaped cloud of fermions revealed a record-fast way of cooling atoms for quantum devices.

PI: Jun Ye | PI: Ana Maria Rey
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Atomic & Molecular Physics | Precision Measurement
Falling Dominos and an Army of Schrödinger’s Cats
generating multiple cat state atoms
Published: July 27, 2020

Using the laser from the strontium optical atomic clock, physicists can generate multiple cat-state atoms quickly and easily.

PI: Ana Maria Rey
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Atomic & Molecular Physics
Phases on the Move: A Quantum Game of Catch
Phase transitions in a dynamic system
Published: April 29, 2020

The world is out-of-equilibrium, and JILA scientists are trying to learn what rules govern the dynamic systems that make our universe so complex and beautiful, from black holes to our living bodies.

PI: Ana Maria Rey | PI: James Thompson
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Atomic & Molecular Physics | Quantum Information Science & Technology
The Power of the Dark Side
Using the Pauli blockade to create a dark state
Published: January 06, 2020

Atoms could live in their excited states forever by reaching a dark state.

PI: Ana Maria Rey
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Atomic & Molecular Physics | Quantum Information Science & Technology
Dancing through dynamical phase transitions in an out-of-equilibrium state
Dynamical phase transitions in an out-of-equilibrium system
Published: August 02, 2019

Using Feshbach resonance, physicists have found that they can control a dynamical phase transition in an out-of-equilibrium state. 

PI: Ana Maria Rey
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Quantum Information Science & Technology
Tying Quantum Knots with an Optical Clock
The optical atomic clock in Jun Ye's lab can create cluster states in milliseconds.
Published: May 22, 2019

Getting a cluster state of perfectly entangled atoms for quantum computing may be easier using a tool in JILA's laboratory.

PI: Ana Maria Rey
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Quantum Information Science & Technology
Chaos reigns in a quantum ion magnet
Rapid scrambling at the edge of a black hole
Published: April 29, 2019

JILA researchers have proposed an experiment that would allow them to study rapid scrambling of quantum information, similar to what happens at the event horizon of a black hole. 

PI: Ana Maria Rey
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Atomic & Molecular Physics | Precision Measurement | Quantum Information Science & Technology
Twisting Atoms to Push Quantum Limits
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Published: August 13, 2018

The chaos within a black hole scrambles information. Gravity tugs on time in tiny, discrete steps. A phantom-like presence pervades our universe, yet evades detection. These intangible phenomena may seem like mere conjectures of science fiction, but in reality, experimental comprehension is not far, in neither time nor space. Astronomical advances in quantum simulators and quantum sensors will likely be made within the decade, and the leading experiments for black holes, gravitons, and dark matter will be not in space, but in basements – sitting on tables, in a black room lit only by lasers.

PI: Ana Maria Rey | PI: James Thompson
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Atomic & Molecular Physics
Quantum Adventures with Cold Molecules
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Published: September 07, 2017

Researchers at JILA and around the world are starting a grand adventure of precisely controlling the internal and external quantum states of ultracold molecules after years of intense experimental and theoretical study. Such control of small molecules, which are the most complex quantum systems that can currently be completely understood from the principles of quantum mechanics, will allow researchers to probe the quantum interactions of individual molecules with other molecules, investigate what happens to molecules during collisions, and study how molecules behave in chemical reactions. 

PI: Ana Maria Rey | PI: John Bohn | PI: Jun Ye
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