**Measurement.** Science is rooted in measurement: it is from measurements, as unified by theory, that understanding is born. Our comprehension of the universe is therefore bounded by our ability to observe and shaped by human creativity. Scientific progress is driven by the identification of new physical systems and measurement techniques, leading to new conceptual understanding. Our experiments use systems of ultracold neutral atoms, quantum gases, that make quantum physics manifest in the laboratory. Many properties of these systems can be understood in the intellectual context of many-body physics which describes systems from the commonplace such as crystals, fluids, and semiconductors, to the extreme such as superconductors, quantum Hall systems, and neutron stars. Many-body physics asks how the properties of individual components — atoms, electrons, nucleons — give rise to the observed macroscopic phenomena.

Ultracold atoms are a very different sort of system than conventional materials, composed of a few hundred to a few hundred million atoms, with densities ranging from 10^{12} cm^{-3} to 10^{15} cm^{-3}, and at temperatures from below 1 nK to a couple uK. These atomic systems are unique in the simplicity of their underlying Hamiltonian along with a singular capacity for controlling and engineering their quantum degrees of freedom.

Our experiments — inspired by the on-going theory efforts of our collaborators world-wide — take place on three distinct apparatuses: RbK, focusing on artificial gauge fields for atomic Bose and Fermi gases; RbChip, creating spin-dependent forces without light; and RbLi, designing long range interactions mediated by particle exchange.

Weakly measuring many-body systems and allowing for feedback in real time can simultaneously create and measure new phenomena in quantum systems. We theoretically study the dynamics of a continuously measured two-component Bose-Einstein condensate (BEC) potentially containing a domain wall and…

Physical systems with non-trivial topological order find direct applications in metrology (Klitzing et al 1980 Phys. Rev. Lett. 45 494–7) and promise future applications in quantum computing (Freedman 2001 Found. Comput. Math. 1 183–204; Kitaev 2003 Ann. Phys. 303 2–30).…

The multiscale entanglement renormalization ansatz (MERA) postulates the existence of quantum circuits that renormalize entanglement in real space at different length scales. Chern insulators, however, cannot have scale-invariant discrete MERA circuits with a finite bond dimension. In this Letter, we…

There have been significant recent advances in realizing band structures with geometrical and topological features in experiments on cold atomic gases. This review summarizes these developments, beginning with a summary of the key concepts of geometry and topology for Bloch…

Gauge fields are ubiquitous in nature. In the context of quantum electrodynamics, you may be most familiar with the photon, which represents the gauge field mediating electromagnetic forces. But there are also gluons, which mediate strong forces, and the W…

Ian was one of eight faculty members in the University of Maryland’s College of Computer, Mathematical, and Natural Sciences are included on Clarivate Analytics’ 2018 list of Highly Cited Researchers, a compilation of influential names in science. https://cmns.umd.edu/news-events/features/4277

We trap individual 1D Bose gases and obtain the associated equation of state by combining calibrated confining potentials with in situ density profiles. Our observations agree well with the exact Yang–Yang 1D thermodynamic solutions under the local density approximation. We find that…

We describe a technique to emulate the dynamics of two-level PT-symmetric spin Hamiltonians, replete with gain and loss, using the unitary dynamics of a larger quantum system. The two-level system in question is embedded in a subspace of a four-level…

Topological order is often quantified in terms of Chern numbers, each of which classifies a topological singularity. Here, inspired by concepts from high-energy physics, we use quantum simulation based on the spin degrees of freedom of atomic Bose-Einstein condensates to…

We describe a novel technique for creating an artificial magnetic field for ultracold atoms using a periodically pulsed pair of counter propagating Raman lasers that drive transitions between a pair of internal atomic spin states: a multi-frequency coupling term. In…