Talks

I will talk about the 1D quantum breakdown model in boson and spin systems, which has an exponential U(1) symmetry with charge decaying exponentially in space. We show that the ground state of the model exhibits a phase transition from a symmetric paramagnetic phase to a quantum breakdown condensate phase that spontaneously breaks the exponential U(1) symmetry. Unconventionally, the condensate phase does not have gapless Goldstone modes, making the spontaneous symmetry breaking stable at zero temperature in 1D. The condensate phase also has an exponentially large ground state degeneracy, which resembles a quantum glass but requires no disorder. This challenges the existing classification schemes of quantum phases of matter.

Gravitational waves (GW) offer a unique window into primordial density perturbations that may differ significantly from the adiabatic fluctuations observed in the CMB and large-scale structure. This raises an exciting prospect of seeing fluctuations of a completely new field from inflation in the anisotropy patterns of GW maps. However, CMB constraints impose an apparent tradeoff between distinctive anisotropy and sizable isotropic signal of such a GW background. I will show that rotating axion-like fields can naturally circumvent this limitation, producing both a strong GW background and large anisotropies within it. I will present the key characteristics of this signal and explore its detection prospects with future GW experiments.

Primordial non-Gaussianities (PNGs) are imprints in the density field caused by particle interactions during the inflationary epoch. A subclass of these signatures ("cosmological colliders") encode information about the interactions and properties of any additional particle fields present during inflation. I introduce a novel method for producing cosmological simulations with arbitrary collider signals, and present signatures from over thirty collider models in the deeply non-linear regime of the density field. I show how weak lensing surveys can offer competitive constraints that are complementary to other probes of PNGs in the late Universe. This simulation framework expands the probes of nonlinear structure (beyond lensing) that are usable in constraining primordial particle physics, which in turn expands the space of testable models and enhances the precision with which we constrain them.

Preparation of thermal and ground states of many-body systems is a central challenge for quantum processors, needed e.g. as the starting point for many quantum physics experiments or for quantum chemistry applications. In this talk, I will discuss recent work on efficient state preparation using engineered system-bath physics. First, I will overview results from the Google experiment [Science 383 6689 2024], where a version of the dissipative algorithm was used to prepare low-energy states of quantum magnetic systems. I will then explain how to modify the algorithm to accurately prepare thermal and ground states [arXiv:2506.21318 & PRX Quantum 6, 010361 2025]: the resulting algorithm is suitable for near-term quantum devices, and exhibits partial robustness to noise owing to the dissipative nature. We demonstrate its efficiency numerically for ground states of 1d chain and ladder systems, and thermal states of the 2D quantum Ising model, providing perturbative arguments for its more general validity.