Spring 2022

Abstract: Models of light-matter interaction with natural atoms typically invoke the dipole approximation, wherein atoms are treated as point-like objects compared with the wavelength of their resonant driving fields. In this talk, we present a demonstration of “giant artificial atoms” realized with superconducting qubits in a waveguide QED architecture. The superconducting qubits couple to the waveguide at multiple, well-separated locations. In this configuration, the dipole approximation no longer holds, and the giant atom may quantum mechanically self-interfere.

Abstract: Semidefinite Programming (SDP) is a class of convex optimization programs with vast applications in control theory, quantum information, combinatorial optimization, machine learning and operational research. In this talk, I will discuss how SDP can be used to address two major challenges in quantum computing research: near-term quantum advantage and device certification.

Abstract: In solid materials, electrons are usually described by the non-relativistic Schrodinger equationsince electron velocity is much slower than the speed of light. However, the relativisticDirac/Weyl equation can emerge as a low-energy effective theory for electrons in certainmaterials. These systems are dubbed “Dirac/Weyl materials” and provide a tunable platformto test quantum relativistic phenomena in table-top experiments. Owing to the linear-inmomentum form, a variety of physical fields, e.g.

Abstract: Squeezing of phonons due to the nonlinear coupling to electrons is a way to enhance superconductivity. In this talk I will present a model of quadratic electron-phonon interaction in the presence of phonon pumping and an additional external squeezing. I will show that the interference between the two driving sources can lead to a stronger electron-electron attraction. This allows for the enhancement of superconductivity, which is shown to be maximal on the boundary with the dynamic lattice instabilities caused by driving.

Abstract: Split detection is a standard experimental scheme for measuring positional displacements. In a typical setup, a laser beam is reflected from the object being probed and then sent to a photodetector that is split into left (L) and right (R) halves: the normalized difference signal (R-L)/(R+L) is then proportional to the object’s horizontal displacement. The maximum precision achievable using this method is limited by the inverse of the beam width.

Dissertation Committee Chair: Professor Maissam Barkeshli
Committee:     
Professor Sankar Das Sarma          
Professor Jay Deep Sau
Professor Michael Gullans
Professor Mohammad Hafezi

Real-time control software and hardware is essential for operating modern quantum systems. In particular, the software plays a crucial role in bridging the gap between applications and real-time operations on the quantum system. Unfortunately, real-time control software is an often underexposed area, and many well-known software engineering techniques have not propagated to this field. As a result, control software is often hardware-specific at the cost of flexibility and portability.

Abstract: In this talk, I will focus on topological order and error correction on fractal geometries.  Firstly, I will present a no-go theorem that Z_N topological order cannot survive on any fractal embedded in two spatial dimensions and then show that for fractal lattice models embedded in 3D or higher spatial dimensions, Z_N topological order survives if the boundaries on the holes condense only loop or membrane excitations.  Next, I will discuss fault-tolerant logical gates in the Z_2 version of these fractal models, which we name as fractal surface codes, using their connection to glob

Abstract: I will discuss entanglement quantities in two-dimensional topologically-ordered phases that can potentially capture correlations beyond what bipartite entanglement entropy can. Specifically, I will present the calculations of the reflected entropy and entanglement negativity for topological ground states when we consider two spatial sub regions. I will also discuss applications of these ideas to one-dimensional quantum lattice many-body systems.
Location: ATL 4402

Abstract: Can a material be made of light? Can quantum mechanics help us measure time? These are two questions in quantum science that I directly address using the tools of atomic physics and quantum optics. We first explore the requirements to make a quantum Hall material made of light. We trap photons inside of a curved-mirror non-planar optical resonator to confine the transverse motion of photons and imbue them with an effective mass and an effective magnetic field for photons.