Spring 2023

Rhombohedral graphenes host van Hove singularities near the band edge which have been found to host magnetism and superconductivity.  These systems have no no moire superlattice, and a ballistic mean free path far exceeding device dimensions, allowing precise measurements of the interplay of different symmetry breaking orders, including a cascade of half- and quarter metals with broken spin and/or valley symmetry as well as both spin-singlet and spin-triplet superconducting states.  I will provide an overview of the physics of these systems, focusing on some r

Abstract: Interaction between individual photons forms the foundation of gate-based optical quantum computing among other quantum-enabled technologies. Quantum emitter-mediated photon interactions are fundamentally constrained by stringent operation conditions and the available photon wavelength and bandwidth, posing difficulty in upscaling and practical applications.

In an isolated quantum many-body system undergoing unitary evolution, the entropy of a subsystem (smaller than half the system size) thermalizes if at long times, it is to leading order equal to the thermodynamic entropy of the subsystem at the same energy. We prove entropy thermalization for a nearly integrable Sachdev-Ye-Kitaev model initialized in a pure product state. The model is obtained by adding random all-to-all 4-body interactions as a perturbation to a random free-fermion model.

Understanding the Hubbard model is crucial for investigating various quantum many-body states and its fermionic and bosonic versions have been largely realized separately. Recently, transition metal dichalcogenides heterobilayers have emerged as a promising platform for simulating the rich physics of the Hubbard model. In this work, we explore the interplay between fermionic and bosonic populations, using a WS2/WSe2 heterobilayer device that hosts this hybrid particle density.

Abstract: Fabry-Perot based refractometry is a powerful technique for pressure assessments that, due to the recent redefinition of the SI system, offers a new route to realizing the SI unit of pressure, the Pascal. In the talk, I will provide a short introduction to pressure metrology and attempt to explain the basics of Fabry-Perot based refractometry and how it can be used to realize the Pascal.

Can the current generation quantum computers solve science problems that conventional computers cannot? The jury is still out on this, but key to achieving this goal is the ability to perform robust quantum computation on near-term hardware.

Hamiltonian simulation is one of the most promising applications of quantum computing. Recent experimental results suggest that continuous-time analog quantum simulation would be advantageous over gate-based digital quantum simulation in the Noisy Intermediate-Size Quantum (NISQ) machine era. However, programming such analog quantum simulators is much more challenging due to the lack of a unified interface between hardware and software, and the only few known examples are all hardware-specific.

Over the past 6 years, a series of works have shown unconditional separations between the computational power of constant depth quantum and classical circuits. This talk will begin with a review of these circuit classes and separations. Then we'll discuss some tips and tricks -- essentially circuit identities -- which are useful when constructing constant depth quantum circuits with superclassical computational power.

Quantum query complexity is a fundamental model in quantum computation, which captures known quantum algorithms such as Grover's search algorithm, and also enables rigorous comparison between classical and quantum models of computation. The polynomial method has become one of the main paradigms for proving lower bounds on quantum query complexity.

A spontaneous symmetry-breaking order is conventionally described by a tensor-product wave-function of some few-body clusters. We discuss a type of symmetry-breaking orders, dubbed entanglement-enabled symmetry-breaking orders, which cannot be realized by any tensor-product state. Given a symmetry breaking pattern, we propose a criterion to diagnose if the symmetry-breaking order is entanglement-enabled, by examining the compatibility between the symmetries and the tensor-product description.