quantum information science

Akers

mhermele — Wed, 08 Jan 2025 13:24:37 +0000

Chris Akers

Affiliations

Fellow of CTQM
Assistant Professor, Department of Physics, University of Colorado Boulder

Bio

I am interested in combining quantum mechanics and gravity, especially by thinking about quantum mechanical aspects of black holes and the AdS/CFT correspondence (our best theory of quantum gravity so far).

To this end, I often use the tools of quantum information theory and quantum computation, and I am interested in expanding these connections. How can quantum computers be used to help the study of quantum gravity? In what ways does quantum gravitational physics affect the theory of computation?

CTQM Role

CTQM Fellow

Research Category

high energy physics

quantum information science

chris.akers@colorado.edu

Gao

mhermele — Wed, 08 Jan 2025 13:18:12 +0000

Xun Gao

Affiliations

Fellow of CTQM
Associate Fellow of JILA
Assistant Professor, Department of Physics, University of Colorado Boulder

Bio

My research interests lie in finding quantum computational advantages, especially for solving practical problems. Examples include the power & limitations of near-term quantum devices, quantum machine learning and quantum optimization algorithms. I would also like to explore quantum error correction and quantum-inspired approaches to design classical algorithms.

CTQM Role

CTQM Fellow

Research Category

quantum information science

xun.gao@colorado.edu

Rey

kdcadmin — Thu, 23 Mar 2023 18:24:18 +0000

Ana Maria Rey

Affiliations

Fellow of CTQM
Fellow of JILA
Adjoint Professor, Department of Physics, University of Colorado Boulder

Bio

My main research interest is ultracold atoms and molecules loaded in optical lattices, which are periodic trapping potentials created by illuminating the atoms and molecules with laser beams. Atoms in optical lattices are analogous to electrons in solid state crystals. Their big advantage is that these "artificial crystals of light" are perfectly clean and highly controllable. Therefore, they are ideal for exploring a whole range of fundamental phenomena that are extremely difficult — or impossible — to study in traditional condensed matter systems. My goal is to study how to control and manipulate these systems to engineer different quantum phases such as superfluids, insulators, quantum magnets, and topological matter. I plan to use them for understanding the physics of strongly correlated bosonic and fermionic systems and nonequilibrium phenomena. Additionally, I am interested in studying how to generate and manipulate entanglement in quantum systems for use in quantum information processing and precision measurements.

CTQM Role

CTQM Fellow

Research Category

atomic, molecular, and optical physics

quantum information science

arey@jilau1.colorado.edu

Phone

303-492-8089 (office)

Website

https://jila.colorado.edu/arey

Knill

kdcadmin — Thu, 23 Mar 2023 17:46:28 +0000

Emanuel Knill

Affiliations

Fellow of CTQM
Scientist/Fellow, National Institute of Standards and Technology

Bio

My research includes developing and applying mathematical and physical tools to better understand the limitations and utilize the capabilities of information processing resources. I use ideas and results from discrete mathematics, linear and multilinear algebra, information theory, probability theory, the theory of computation, and mathematical/theoretical physics. Current areas of interest include high-significance tests of quantum mechanics, characterization and benchmarks for digital and analog quantum devices, quantum measurement theory, emergence of subsystems in quantum matter and fields, and algebraic quantum information. Most of my work is available at arXiv.org.

CTQM Role

CTQM Fellow

Research Category

quantum information science

knill@boulder.nist.gov

Website

http://www.eskimo.com/~knill/

Holland

kdcadmin — Wed, 15 Mar 2023 17:37:48 +0000

Murray Holland

Affiliations

Fellow of CTQM
Fellow of JILA
Professor, Department of Physics, University of Colorado Boulder

Bio

My research involves theoretical studies of Bose-Einstein condensation, including (1) the modes of oscillation, (2) the quantitative effect of interactions and loss processes, (3) the behavior of a condensate undergoing evaporative cooling, and (4) the thermodynamics of a small number of atoms. My future research interests include the damping processes of coherent excitations, quantum diffusion of the condensate phase, and new methods for treating quantum kinetic theory. I also investigate quantum optics, in which I study the properties of laser fields and their interaction with matter. My other interests include optical cavities and their interaction with atomic beams and quantum measurement theory.

CTQM Role

CTQM Fellow

Research Category

atomic, molecular, and optical physics

quantum information science

mholland@jila.colorado.edu

Phone

303-492-4172 (office)

Website

http://jila.colorado.edu/holland

Quantum Information Science

kdcadmin — Thu, 09 Mar 2023 21:44:35 +0000

Quantum Information Science kdcadmin Thu, 03/09/2023 - 2:44 pm

A fundamental assumption of quantum information science is that there are degrees of freedom in quantum matter with long-lived coherence suitable for realizing controllable quantum bits--the fundamental information units of quantum information and computation. The existence of such degrees of freedom and the irreducibly quantum features of their states reveals fundamental features of the underlying physics. Thus, quantum information provides a framework for investigating the control and measurement of quantum matter and provides new insights into its states and phases.

Work at the CTQM involving quantum information includes the theory needed to control and characterize trapped ion and atom systems, the use of these systems for ``digital'' and ``analog'' simulations of models of quantum matter beyond the ability of classical simulations, the study of fundamentally quantum correlations and their role in phases of quantum matter, and investigations of the requirements for and properties of emergent and engineered quantum subsystems.

CTQM Fellow(s)

The Quantum Identity Crisis

kdcadmin — Wed, 15 Oct 2014 17:28:27 +0000

The Quantum Identity Crisis kdcadmin Wed, 10/15/2014 - 11:28 am

The laws of quantum mechanics make it impossible to determine the exact time during the synchronization (merger) of two atomic clocks (top panel) into one (bottom panel). As the clocks get closer and closer together, quantum noise skyrockets because of the uncertainty of whether the clocks will merge or stay separate (middle panel).

Image Credit

The Holland group and Steve Burrows

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.

For instance, one kind of quantum phase transition takes place when a researcher uses lasers to force atoms from a Bose-Einstein condensate (BEC) inside a “crystal” of light, where the atoms solidify into a lattice pattern. Because the ground state arrangement of the atoms has totally changed from the indistinct blur of a BEC to a regular array inside the light crystal, the physical manifestation of the atoms is completely different.

We now know that quantum phase transitions also occur in dynamical systems, thanks to the Holland group. Dynamical systems are systems that can be a long way from equilibrium, like atomic clocks clocks that are always evolving in time, or superradiant lasers that have photons continuously moving in and out of them. Not surprisingly, all sorts of things happen in such dynamical systems when they change their quantum phase. The new understanding of dynamical quantum phase transitions was gained during the Holland group’s theoretical investigation of the quantum aspects of classical synchronization.

Classical synchronization theory explains why fireflies suddenly start emitting light simultaneously, crickets spontaneously sing in unison, metronomes or pendulum clocks synchronize their ticking (if they’re physically connected), or why audiences clap in unison after a minute or two. To study the effects of quantum synchronization as compared to ordinary, everyday synchronization, the Holland group looked at what would happen if two atomic clocks containing identical ensembles of atoms moved close enough to one another to merge into a single, larger atomic clock.

The group discovered that things got really interesting when the clocks moved very close together. Suddenly, it was as if every atom in both clocks was trying to decide, “Should I be in a separate clock or in one clock?” The quantum noise from this process went off scale! The clocks, which had been accurate, with nice sharp, narrow hands, became so noisy and fuzzy that it was impossible to determine the exact time. The clocks had moved into the region of “quantum criticality.” And in the quantum criticality region, the uncertainty inherent in the laws of quantum mechanics is in full play.

Interestingly, when the two clocks finally “decided” to become a single, larger clock, everything quickly settled back down. The hands on the new clock became narrow and sharp as soon as the quantum phase transition was complete. The new, stable quantum phase was a larger atomic clock containing a completely restructured—and synchronized— ensemble of atoms.

The researchers responsible for this new understanding of quantum synchronization during a dynamical phase transition include graduate students Minghui Xu and Dave Tieri, former graduate student Elizabeth Fine, as well as Associate Professor Adjoint of Physics James K. Thompson and Professor of Physics and CTQM Fellow Murray Holland.

Their work promises to impact research well beyond physics as quantum synchronization is thought to play important roles in brain activity as well as in photosynthetic light harvesting and energy transfer. Because it is also involved in the transition between superconductivity and Mott-insulating behavior in copper-containing metals, quantum synchronization may be an important factor in the design of advanced electronic devices.

Principal Investigators

Murray Holland

Research Topics

quantum information science

New Flavors of Quantum Magnetism

kdcadmin — Thu, 24 May 2012 17:18:45 +0000

New Flavors of Quantum Magnetism kdcadmin Thu, 05/24/2012 - 11:18 am

Artist's conception of a 3-dimensional optical lattice.

Image Credit

The Rey Group and Brad Baxley

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.

When people normally think about magnetism, they often think of the two most common magnetic flavors: spin up and spin down. And, when the spins of billions and billions of iron atoms all line up in one of these two directions, the result is the familiar bar magnet.

But things are never so simple and straightforward in the quantum world. It’s as if in addition to spin up and spin down in alkaline earth atoms, there were also eight more unique spin directions such as spin forwards, spin backwards, or spin diagonal. (Of course, in this case, the spin directions are just a convenient analogy for quantum spin states.)

The multi-flavored alkaline earth atoms have some real advantages in quantum simulation. Inside a simulator, a set number of alkaline-earth atoms with ten flavors can actually make the whole system get five times colder than the same number of atoms with only two flavors. This result was entirely unexpected.

Conventional wisdom said that a higher number of magnetic flavors in the atomic nuclei would cause the lowest-possible temperature of the system to be higher than that of a system with a lower number of magnetic flavors!

“I was so shocked when we first saw this, I spent a whole day trying to find the error in my calculation,” said Kaden Hazzard, an NRC (National Research Council) postdoc with the Rey group. But, Hazzard hadn’t made a mistake. The Rey group has proved conventional wisdom wrong — and opened the door to some novel experiments with the quantum simulator in the Ye lab.

Since the simulator is already kept at ultracold temperatures, the newly discovered relationship of cooling to an increased number of spin states means that it should theoretically be possible to cool highly controlled atoms down to nano-Kelvin temperatures. Such temperatures are needed to directly observe quantum magnetism in action.

“When you get alkaline earth atoms really cold, that’s when you can see the most interesting physics,” Hazzard said.

Because of the unique properties of alkaline earth atoms, scientists will soon be able to study what happens when different magnetic flavors interact and produce spin ordering. For instance, as a simulator gets colder, random flavors may take on their preferred spin direction at regular intervals inside a three-dimensional lattice, like the one shown in the figure.

This behavior will set the stage for the creation of antiferromagnets and spin liquids. In antiferromagnets, random magnetic flavors assume their preferred directions at utralow temperatures of below 1 nK. Spin liquids can occur when interactions or geometrical factors frustrate the antiferromagnetic order, causing it to “ melt.” In the resulting spin liquid, spins can fluctuate through different states even near a temperature of absolute zero.

Antiferromagnets and spin liquids have not yet been observed in the laboratory. But, the Rey group’s predictions give hope that they soon may be seen soon in simulators using alkaline earth atoms.

The work on the new flavors of quantum magnetism was done by Hazzard, CU Associate Research Professor of Physics Ana Maria Rey, CU Associate Professor of Physics Victor Gurarie and CU Professor of Physics Michael Hermele. Rey, Guarie, and Hermele are also CTQM Fellows. Research associates Salvatore Manmana and Gang Chen as well as colleague Adrian Feiguin of the University of Wyoming worked with Hazzard and Rey on foundational work for the new theory. The Rey group is continuing its investigations of quantum magnetism with colleagues in Germany and Austria.

Principal Investigators

Ana Maria Rey

Michael Hermele

Research Topics

quantum information science