Murray Holland

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)

Atomic, Molecular, and Optical Physics

kdcadmin — Thu, 09 Mar 2023 21:38:45 +0000

Atomic, Molecular, and Optical Physics kdcadmin Thu, 03/09/2023 - 2:38 pm

Atomic, molecular and optical physics research interests are on developing ways to dynamically manipulate, control and understand interacting atomic molecular and optical systems. The main goals are to use them as quantum simulators of solid state materials and high energy systems, as quantum information processors, and to engineer improved quantum devices and technologies such as ultra-precise atomic clocks and quantum sensors. Topics at the top of our research priorities are: orbital quantum magnetism, quantum metrology with many-body states, topological quantum matter and non-equilibrium open driven quantum systems.

CTQM Fellow(s)

Ana Maria Rey

Murray Holland

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

Dealing with Loss

kdcadmin — Wed, 05 Mar 2014 18:06:21 +0000

Dealing with Loss kdcadmin Wed, 03/05/2014 - 11:06 am

By continuously measuring ultracold KRb molecules in tubes (with weak lattices) created by intersecting laser beams, researchers suppress the loss of the molecules during experiments. The loss suppression is due to the quantum Zeno effect.

Image Credit

The Ultracold Molecule Collaboration and Brad Baxley,

There’s exciting news from JILA’s ultracold molecule collaboration. The Jin, Ye, Holland, and Rey groups have come up with new theory (verified by experiment) that explains the suppression of chemical reactions between potassium-rubidium (KRb) molecules in the KRb quantum simulator. The main reason the molecules do not collide and react is continuous measurement of molecule loss from the simulator. That it works this way is a consequence of the quantum Zeno effect, also known as the watched pot effect, as in the proverb “A watched pot never boils.”

In essence, if researchers investigate a quantum system by continuously measuring it, things stop changing altogether. The strange laws of quantum mechanics are responsible for this odd behavior. These laws dictate that the act of measurement itself forces the KRb molecules into a particular quantum state. And, if measurements occur continuously, the molecules will stay in that state because the measurements themselves are collectively preventing any change in the quantum states of the molecules. The idea that continuous measurements prevent a quantum system from evolving is the essence of the quantum Zeno effect, named for the Greek philosopher Zeno of Elea.

Thus, if you adjust a quantum simulator so that (according to the laws of classical physics) the molecules inside it get lost faster and faster because of colliding and reacting, then the laws of quantum mechanics will actually make the molecules react slower and slower until they eventually just sit there forever and never get lost. It’s almost as if two KRb molecules “know” from the continuous measurements not to hop into the same place in the simulator because they would react and disappear if they did. New theory by the Holland and Rey groups shows explicitly how this works. It not only verifies the quantum Zeno effect, but also demonstrates that older theories that attempted to explain this kind of quantum behavior incorrectly predicted loss to happen five times faster.

In practical terms, the previous and less accurate theories suggested that the number of KRb molecules in the simulator would be about one molecule per two lattice sites (which are energy wells created by intersecting laser beams). In practice, however, that calculation predicted too many molecules. Right now, the number of KRb molecules in the simulator is fewer, typically one per every 10 lattice sites. And, this just happens to match the amount of lattice filling predicted by the new theory. Clearly, increasing the lattice filling is going be a lot harder than researchers originally expected it to be.

Untangling this complicated quantum behavior required the brainpower and dedication of 13 JILA researchers. The theory team comprised graduate student Bihui Zhu, recently minted Ph.D. Michael Foss-Feig, research associates Johannes Schachenmayer and Michael Wall, senior research associate Kaden Hazzard as well as CU Professor of Physics Murray Holland and CU Associate Research Professor of Physics Ana Maria Rey. Holland and Rey are CTQM Fellows. The experimental team included research associates Bryce Gadway and Bo Yan, graduate students Steven Moses and Jacob Covey, and Fellows Debbie Jin and Jun Ye.

Principal Investigators

Ana Maria Rey

Murray Holland

Research Topics

atomic, molecular, and optical physics

Quantum Legoland

kdcadmin — Mon, 01 Jul 2013 16:45:46 +0000

Quantum Legoland kdcadmin Mon, 07/01/2013 - 10:45 am

Artist’s concept of the quantum building blocks of a laser.

Image Credit

The Holland group and Brad Baxley

The quantum world is not quite as mysterious as we thought it was. It turns out that there are highways into understanding this strange universe. And, graduate students Minghui Xu and David Tieri with Fellow Murray Holland have just discovered one such superhighway that has been around since the 1950s. Traveling along this superhighway has made it possible to understand the quantum behavior of hundreds of atoms inside every laser used in JILA, including the superradiant laser in the Thompson lab that works entirely differently from all the others.

The weirdest thing is that this is the same superhighway traveled by the SU(4) group theory used to explain quark physics. Quarks are elementary particles that make up hadrons; hadrons are things like the protons and neutrons that sit inside every atomic nucleus. The lowest energy quarks are known as up, down, strange, and charm. And, as it turns out, up, down, strange, and charm quarks are analogs of the four basic “Lego building blocks” that also describe the quantum behavior of atoms in a laser.

So why is it so hard to figure out what’s happening with hundreds of atoms inside a laser? The answer is easy. It’s the fault of quantum mechanics and its mind-boggling complexity. A mere three hundred atoms, each with two possible states, have as many different combinations of quantum states as there are atoms in the entire Universe.

Fortunately, CTQM Fellow Murray Holland and graduate students Minghui Xu and David Tieri have just found a pathway through this complexity. This pathway exists because of something called invariance. Invariance is responsible for the familiar laws of conservation of energy and conservation of momentum that govern the classical world we are more familiar with. The two laws state that if no external forces are acting on a system, (1) the amount of energy remains constant over time and (2) an object will continue moving at the same speed forever. The fact that energy remains constant is due to the invariance of choosing the origin of time. The fact that an object just keeps going at the same speed is due to the invariance of choosing the origin of space.

As it turns out, the Holland group has just discovered an intricate invariance that governs the quantum physics of lasers. As “luck” would have it, only a relatively small number of possible quantum states are compatible with a particular value of the invariant quantity once it’s determined by a laser system itself.

It’s as if a laser can “choose” to be made of only one color such as red, blue, green, yellow, black, grey, or clear Legos. But, once decided, the laser obeys a conservation law that means that the color of the Lego blocks won’t change in time. The constancy of the color represents the invariance. Once the invariance is in place, one can make any state of a laser from just four shapes of quantum Lego blocks, a square (up), a corner piece (down), a thin arch piece (strange) and a rectangle (charm).

Of course, like quarks, the laser analogs (Lego shapes) are actually quantum mechanical states. But, it’s possible to construct quite complicated things from four elementary building blocks.

“We’ve got four types of blocks, and, out of them, we can make everything, Holland explains. “When you realize this, there is a clear path to an unbelievable reduction in complexity.”

Holland and his students have just proved this assertion in a new Physical Review A paper. In the paper, they showed how “quark physics” mathematics could be used to solve the quantum master equations for both ordinary and superradiant lasers, feats once considered impossible.

The new theory opens the door to finding ways to build even more complicated structures out of the basic four quantum Legos. Plus, new building blocks, such as laser analogs of the much heavier top and bottom quarks, may be found.

“We already know there are some optical systems where the building blocks are slightly different,” Holland says. “The questions are: How far can we push this new idea? Can we use our new theory to understand other important systems in quantum optics and ultracold gases?”

Perhaps an important question for the rest of us to ponder is: Without invariances, would we even have the world we know?

Principal Investigators

Murray Holland

Research Topics

atomic, molecular, and optical physics