Contact
Email: xiangyu.cao [at] phys.ens.fr
Office: E254, 24 rue Lhomond, Paris
(I am also a regular visitor of LPTMS)
Research news
My papers can be found on Google Scholar.
[August 2025] With Benoît Ferté (PhD student at ENS) and Davide Farci (Master student from Florence) we posted a preprint about decoherent histories and quantum Darwinism. TL;DR: A measurement apparatus is a macroscopic object, but every macroscopic object is not a measurement apparatus!
http://arxiv.org/abs/2508.16482
[July 2025] I posted a short note on the quantum dynamical entropy of Connes, Narnhofer and Thirring (CNT). This work is part of my ongoing effort of « decoding » the mathematical literature on quantum dynamical entropies. Here, I show that a simplified version of the CNT entropy can be defined in the setup of monitored quantum dynamics. Furthermore, I find an exact formula for the entropy rate that applies to the continuous monitoring of a « coarse-grained » observable in many-body systems. Using this formula I conjecture that the entropy rate satisfies a Planckian bound in a thermal state, reminiscent of the Planckian bound on chaos or on viscosity.
https://arxiv.org/abs/2507.20914
[October 2024] With Ayush De, Umberto Borla, and Snir Gazit at the Racah Institute of Physics (Hebrew University of Jerusalem), we put forward a new Quantum Monte Carlo algorithm that samples paths of operator growth. The method allowed to check the hypothesis formulated in this work to unprecedented precision. The paper now published in PRB.
https://arxiv.org/abs/2401.06215 [PRB]
[March 2024] The two companion papers (with Benoît Ferté) on Quantum Darwinism-encoding transitions are published in Physical Review Letters and Physical Review A, respectively.
Seminar videos with new results: [Les Houches] [EPFL (Bernoulli center)]
https://arxiv.org/abs/2305.03694 [PRL]
https://arxiv.org/abs/2312.04284 [PRA]
[August 2023] Our paper on « deep Hilbert space » with Zihao Qi (Caltech) and Thomas Scaffidi (Toronto, UC Irvine) is published in PRB and selected as an Editors’ Suggestion!