Physics Department Colloquium

Quantum Logic Control of a Single Molecular Ion

An amazing level of quantum control is routinely reached in modern experiments with atoms, but similar control over molecules has been an elusive goal. We recently proposed a method based on quantum logic spectroscopy [1] to address this problem for a wide class of molecular ions [2]. We have now realized the basic elements of this proposal. In our demonstration, we trap a calcium ion together with a calcium hydride ion (CaH+) that is a convenient stand-in for more general molecular ions.

New results from the NOvA neutrino oscillation experiment

Neutrino oscillations provide the first hints at physics beyond the standard model of particle physics. Current and future neutrino experiments aim to further refine our understanding of neutrino mixing and reveal the remaining unknowns in the process. Precision measurements in long-baseline accelerator experiments could help answer profound questions about the origin and evolution of our universe, including the assymetry of matter over antimatter.

Engineering Trapped-Ion Systems for Large Scale Quantum Simulation

Laser cooled trapped ions offer unprecedented control over both internal and external degrees of freedom at the single-particle level. They are considered among the foremost candidates for realizing quantum simulation and computation platforms that can outperform classical computers at specific tasks. In this talk I will show how linear arrays of trapped 171Yb+ ions can be used as a versatile platform for studying quantum dynamics of strongly correlated many-body quantum systems.

Measurement of the fine-structure constant as a test of the Standard Model

Measurements of the fine-structure constant alpha require methods from several subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: alpha = 1/137.035999046(27) at 2.0 x 10^-10 accuracy.

Quantum nanophotonics: engineering atom-photon interactions on a chip

The ability to engineer controllable atom-photon interactions is at the heart of quantum optics and quantum information processing. In this talk, I will introduce a nanophotonic platform for engineering strong atom-photon interactions on a semiconductor chip. I will first discuss an experimental demonstration of a spin-photon quantum transistor [1], a fundamental building block for quantum repeaters and quantum networks. The device allows a single spin trapped inside a semiconductor quantum dot to switch a single photon, and vice versa, a single photon to flip the spin.

Ultracold Molecules: From Quantum Chemistry to Quantum Computing

Abstract: Cooling atomic gases to quantum degeneracy opened the new field of quantum simulation. Here the precise tools of atomic physics can be used to study exotic models from condensed matter or nuclear physics with unique tunability and control. Ultracold molecules bring many new possibilities to quantum simulation. I will review the physics of ultracold molecules, including our recent production of stable, ultracold triplet molecules and what they can add to quantum simulation.

Understanding and Predicting Turbulent Transport in Tokamak Plasmas

In magnetically confined fusion plasmas like tokamaks, transport of heat and particles is dominated by turbulence. Turbulent transport models can be validated using experimental data, using a rigorous methodology and direct comparisons with turbulence measurements.  While the transport models capture details of the turbulence very well, and can be used to predict steady-state temperature profiles for ITER and SPARC and other future tokamaks, there remain several outstanding questions.

Magic Angle Graphene: a New Platform for Strongly Correlated Physics

The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, based on graphene moiré superlattices. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system.

New opportunities in dark matter at accelerators

The program to search for dark matter in the past couple of decades has mostly focused on the WIMP (weakly interacting massive particle) at the GeV - TeV scale. It has made impressive strides in sensitivity but has yet to unearth the particle nature of dark matter. Recently there have been many new initiatives to broaden the search for dark matter, many of them smaller scale experiments.