Talks

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.

In this talk, we analyze detector operators that measure energy to the power ∆-2 at null infinity in Einstein gravity. These operators transform as conformal primaries on the celestial sphere and provide a natural basis for describing energy-flux observables in scattering processes. Using the collinear factorization of scattering amplitudes, we derive the universal leading structure of the operator product expansion (OPE). A key consequence of our analysis is the precise identification of the ∆=2 detector, the number operator. Exploiting the fact that soft charges generate symmetries of the S-matrix, we demonstrate that the number of particles is entirely determined by the product of two supertranslation currents. This work establishes a direct link between detector observables and the soft sector of celestial holography. Analogous conclusions hold for Yang–Mills theory.