Research Highlights

Precision Measurement | Quantum Information Science & Technology
Twisting and Binding Matter Waves with Photons in a Cavity
Atoms inside of an optical cavity exchange their momentum states by "playing catch" with photons. As the atoms absorb photons from an applied laser, the whole cloud of atoms recoil rather than the individual atoms.
Published: April 28, 2024

Precisely measuring the energy states of individual atoms has been a historical challenge for physicists due to atomic recoil. When an atom interacts with a photon, the atom “recoils” in the opposite direction, making it difficult to measure the position and momentum of the atom precisely. This recoil can have big implications for quantum sensing, which detects minute changes in parameters, for example, using changes in gravitational waves to determine the shape of the Earth or even detect dark matter. 

In a new paper published in the Science, JILA and NIST Fellows Ana Maria Rey and James Thompson, JILA Fellow Murray Holland, and their teams proposed a way to overcome this atomic recoil by demonstrating a new type of atomic interaction called momentum-exchange interaction, where atoms exchanged their momentums by exchanging corresponding photons. 

Using a cavity—an enclosed space composed of mirrors—the researchers observed that the atomic recoil was dampened by atoms exchanging energy states within the confined space. This process created a collective absorption of energy and dispersed the recoil among the entire population of particles.

PI: Ana Maria Rey | PI: James Thompson | PI: Murray Holland
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Precision Measurement | Quantum Information Science & Technology
B-C-S—Easy as I, II, III: Unveiling Dynamic Superconductivity
Researchers observed the dynamic phases of BCS superconductor interactions in a Cavity QED by measuring the light leakage from the cavity.
Published: January 24, 2024

In physics, scientists have been fascinated by the mysterious behavior of superconductors—materials that can conduct electricity with zero resistance when cooled to extremely low temperatures. Within these superconducting systems, electrons team up in “Cooper pairs” because they're attracted to each other due to vibrations in the material called phonons. 

As a thermodynamic phase of matter, superconductors typically exist in an equilibrium state. But recently, researchers at JILA became interested in kicking these materials into excited states and exploring the ensuing dynamics. As reported in a new Nature paper, the theory and experiment teams of JILA and NIST Fellows Ana Maria Rey and James K. Thompson, in collaboration with Prof. Robert Lewis-Swan at the University of Oklahoma, simulated superconductivity under such excited conditions using an atom-cavity system. 

PI: Ana Maria Rey | PI: James Thompson
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Atomic & Molecular Physics | Quantum Information Science & Technology
The Tale of Two Clocks: Advancing the Precision of Timekeeping
A photo of the atomic clock setup complete with the bisecting cavity.
Published: January 11, 2024

Historically, JILA (a joint institute established by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder) has been a world leader in precision timekeeping using optical atomic clocks. These clocks harness the intrinsic properties of atoms to measure time with unparalleled precision and accuracy, representing a significant leap in our quest to quantify the most elusive of dimensions: time.

However, the precision of these clocks has fundamental limits, including the “noise floor,” which is affected by the “quantum projection noise” (QPN). “This comes from the spin-statistics of the individual qubits, the truly quantum nature of the atoms being probed,” elaborated JILA graduate student Maya Miklos. State-of-the-art clock comparisons, like those directed by JILA and NIST Fellow and University of Colorado Boulder Physics professor Jun Ye, are pushing ever closer to this fundamental noise floor limit. However, this limit can be circumvented by generating quantum entanglement in the atomic samples, boosting their stability.

Now, Ye’s team, in collaboration with JILA and NIST Fellow James K. Thompson, has used a specific process known as spin squeezing to generate quantum entanglement, resulting in an enhancement in clock performance operating at the 10-17stability level. Their novel experimental setup, published in Nature Physics, also allowed the researchers to directly compare two independent spin-squeezed ensembles to understand this level of precision in time measurement, a level never before reached with a spin-squeezed optical lattice clock. 

PI: Jun Ye | PI: James Thompson
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Precision Measurement | Quantum Information Science & Technology
Entangled Pairs Get Sensitive Very Fast
A representation of bosonic pair creation, which creates an entangled state between atoms
Published: May 23, 2023

The best clock in the world has no hands, no pendulum, no face or digital display. It is made of ultra-cold atoms trapped by light.  This atomic clock is so precise that, had it begun ticking when Earth formed billions of years ago, it would not yet have gained or lost a second. Nonetheless, this incredible clock, and all atomic clocks, operate with collections of independent atoms, and as a result, their precision is limited by the fundamental laws of quantum mechanics.  One way to get around this fundamental quantum imprecision is to entangle the atoms, or make them talk, in such a way that one cannot describe the individual atoms’ quantum states independently of one another. In this case it is possible to create the situation where the quantum noise of one atom in the clock can be partially canceled by the quantum noise of another atom such that the total noise is quieter than one would expect for independent atoms. One type of entangled state is called a “squeezed state”, which can be visualized as if one had shaped the quantum noise in a way that is narrower in one direction at the expense of making the fuzziness in the adjacent direction worse.  Squeezed states have been realized in several labs around the world at groundbreaking precision levels recorded by several physics institutes, including  at JILA in Boulder, Colorado.  However, squeezing is experimentally challenging to create and there is a need for a variety of “flavors” of squeezing for different types of quantum sensing tasks.

A new approach recently described in Physical Review Letters explores a new way to generate squeezing that is exponentially faster than previous experiments and generates a new flavor of entanglement:  two-mode squeezing—a type of entanglement that is thought to be used for improving the best atomic clocks and for sensing how gravity changes the flow of time. This promising new approach was developed by a collaboration of JILA and NIST Fellows Ana Maria Rey and James K. Thompson, and their team members, along with Bhuvanesh Sundar, a former postdoctoral researcher at JILA now at Rigetti Computing, and former JILA research associate Dr. Robert Lewis-Swan, now an Assistant Professor at the University of Oklahoma.

PI: Ana Maria Rey | PI: James Thompson
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Precision Measurement | Quantum Information Science & Technology
An Entangled Matter-wave Interferometer: Now with Double the Spookiness!
A rendering of the entangled atoms within the interferometer
Published: October 20, 2022

JILA and NIST Fellow James K. Thompson’s team of researchers have for the first time successfully combined two of the “spookiest” features of quantum mechanics to make a better quantum sensor:  entanglement between atoms and delocalization of atoms.  Einstein originally referred to entanglement as creating spooky action at a distance—the strange effect of quantum mechanics in which what happens to one atom somehow influences another atom somewhere else. Entanglement is at the heart of hoped-for quantum computers, quantum simulators and quantum sensors.  A second rather spooky aspect of quantum mechanics is delocalization, the fact that a single atom can be in more than one place at the same time.  As described in their paper recently published in Nature, the Thompson group has combined the spookiness of both entanglement and delocalization to realize a matter-wave interferometer that can sense accelerations with a precision that surpasses the standard quantum limit (a limit on the accuracy of an experimental measurement at a quantum level) for the first time.  By doubling down on the spookiness, future quantum sensors will be able to provide more precise navigation, explore for needed natural resources, more precisely determine fundamental constants such as the fine structure and gravitational constants, look more precisely for dark matter, or maybe even one day detect gravitational waves.

PI: James Thompson
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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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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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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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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 | 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
A Little Less Spontaneous
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Published: June 29, 2018

A large fraction of JILA research relies on laser cooling of atoms, ions and molecules for applications as diverse as world-leading atomic clocks, human-controlled chemistry, quantum information, new forms of ultracold matter and the search for new details of the origins of the universe. JILAns use laser cooling every day in their research, and have mastered arcane details of the process.

PI: James Thompson | PI: Murray Holland
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Laser Physics
Lassoing Colors with Atomic Cowpokes
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Published: July 10, 2017

Getting lasers to have a precise single frequency (color) can be trickier than herding cats. So it’s no small accomplishment that the Thompson group has figured out how to use magnetic fields to create atomic cowpokes to wrangle a specific single color into place so that it doesn’t wander hither and yon. The researchers do this with a magnetic field that causes strontium atoms in an optical cavity to stop absorbing light and become transparent to laser light at one specific color. What happens is that the magnetic field creates a transparent window that serves as a gate to let only light of a single frequency pass through.

PI: James Thompson
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Quantum Information Science & Technology
The Quantum Identity Crisis
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Published: October 14, 2014

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.

PI: James Thompson | PI: Murray Holland
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Atomic & Molecular Physics
Quantum Entanglement
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Published: July 13, 2014

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.

PI: James Thompson
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Laser Physics
The Heart of Darkness
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Published: December 18, 2012

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.

PI: James Thompson
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Atomic & Molecular Physics
The Entanglement Tango
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Published: December 05, 2012

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.

PI: Ana Maria Rey | PI: James Thompson
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Laser Physics
The Laser with Perfect Pitch
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Published: April 04, 2012

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.

PI: James Thompson
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Atomic & Molecular Physics | Precision Measurement
Sayonara Demolition Man
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Published: November 30, 2010

The secret for reducing quantum noise in a precision measurement of spins in a collection of a million atoms is simple: Pre-measure the quantum noise, then subtract it out at the end of the precision measurement. The catch is not to do anything that detects and measures the spins of individual atoms in the ensemble. If states of individual atoms are measured, then those atoms stop being in a superposition and the subsequent precision measurement will be ruined.

PI: James Thompson
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