JQI Seminar

Exploring the effects of geometry, topology, dimensionality, and interactions on ultracold atomic ensembles has proven to be a continually fruitful line of inquiry. One heretofore unexplored configuration for such ensembles is that of a bubble or shell, where trapped atoms are confined in the vicinity of a spherical or ellipsoidal surface.

Looking for some fresh bathroom tiles? Why don't you try regular 7-gons this time, it looks amazing! Only requirement: You'd need to live in hyperbolic space of constant negative curvature. To see how this would be like, let me take you onto a journey into hyperbolic space through recent breakthrough experiments in circuit quantum electrodynamics, where such tilings are realized with superconducting resonators and photons are tricked into believing that space is hyperbolic.

Quantum frequency conversion is the process by which the wavelength of a light field is converted to another wavelength while still fully maintaining its quantum state.  We describe our recent research that utilizes the nonlinear optical process of four-wave mixing to perform ultralow noise quantum frequency conversion with efficiencies approaching 100%.  We also show how this nonlinear process can be used to realize other novel quantum phenomena in the frequency domain including Hong-Ou-Mandel interference, near-deterministic single-photon generation, single-photon Ramsey interference, and

Exotic and counterintuitive phases of quantum matter have been recently discovered in degenerate quantum gases of highly magnetic atoms (Erbium and Dysprosium). The very fact such atoms possess a large magnetic moment means that their interactions at the many-body level and their quantum correlations acquire a unique long-range and anisotropic character. This property opens novel avenues of investigation beyond the contact-interaction paradigm.

Point defects in crystals are the solid state analog to trapped ions. Thus these “quantum defects” have gained popularity as qubit candidates for scalable quantum networks.  In this talk, I will introduce some of the basic quantum defect properties desirable for quantum network applications and give some illustrative examples of recent successes toward scalable quantum networks, highlighting my group’s work on single NV centers in diamond and shallow donors in ZnO.

We are on the verge of a technological revolution. Over the last couple of years the first computational devices have become commercially available that promise to exploit so-called quantum advantage. Even though the thermodynamic cost for processing classical information has been known since the 1960s, the thermodynamic description of quantum computers is still at its infancy. This is due to the fact that many notions of classical thermodynamics, such as work and heat, do not readily generalize to quantum systems in the presence of thermal and quantum noise.

A spatially oscillating pair potential drives a deconfinement transition of the Majorana bound states in the vortex cores of a Fu-Kane heterostructure (a 3D topological insulator on a superconducting substrate, in a perpendicular magnetic field). In the deconfined phase at zero chemical potential the Majorana fermions form a dispersionless Landau level, protected by chiral symmetry against broadening due to vortex scattering.

Memory devices are responsible for a significant fraction of the energy consumed in electronic systems- typically 25% in a laptop and 50% in a server station. Reducing the energy consumption of memories is an important goal. For the evolving field of artificial intelligence, the compatible devices must simulate a neuron. We are working on three different approaches towards these problems- one involving an organic metal centred azo complex, the other involving oxide based ferroelectric tunnel junctions and the last involving real live neuronal circuits. 
 

The talk presents theorems comparing continuum one-electron models of graphene with tight binding and other approximations. Joint work with Micael Weinstein, James Lee-Thorp and Jacob Shapiro.

 Fermionic atoms in optical lattices have served as a useful model system in which to study and emulate the physics of strongly correlated matter. Driven by the advances of high-resolution microscopy, the current research focus is on two-dimensional systems, in which several quantum phases—such as antiferromagnetic Mott insulators for repulsive interactions and charge-density waves for attractive interactions—have been observed.