When Incoherence Creates Coherence: Quantum Coherence in a Hot, Strongly Coupled Environment
Pat Kambhampati
Professor
Department of Chemistry
McGill University
September 15, 2026
10:30 a.m.
In-person:C2-361
Abstract: Quantum coherence in a system is conventionally understood as something that must be protected from its environment via decoupling of the two. Modern quantum technologies therefore go to extraordinary lengths to suppress environmental interactions: superconducting qubits are cooled to millikelvin temperatures, atoms and ions are isolated in vacuum, and optical cavities create carefully controlled electromagnetic environments. The physical intuition is compelling: thermal fluctuations randomize quantum phase, system–bath coupling produces dephasing, and incoherence destroys coherence. Chemistry, however, lives in almost exactly the opposite regime. Molecules and materials are embedded in strongly interacting, structurally dynamic, thermally populated environments. This raises a provocative question: can the very interactions expected to produce incoherence instead become the mechanism by which coherence emerges?
We explore this question in soft lead-halide perovskite quantum materials using ultrafast multidimensional coherent spectroscopy, transient absorption, and time-resolved photoluminescence. Here, strong electron–phonon coupling causes photoexcitation to reorganize the fluctuating lattice and generate a dynamic polaronic field. Our experiments indicate that this field does more than perturb or dephase the electronic system: it can organize otherwise disordered dipoles into collective, phase-correlated quantum states and protect the resulting coherence. I will connect this emerging picture to Dicke physics, superradiance, superabsorption, and decoherence-protected subspaces. Rather than treating the bath solely as an adversary to be eliminated, these results suggest a different paradigm for quantum materials: under strong coupling, the source of incoherence can itself become the organizing field from which coherence emerges.