The Quantum - Classical Boundary: understanding, concepts, and language

Project Summary

Quantum theory explains the behaviour of atoms and molecules, yet the everyday world appears classical: objects have definite shapes, trajectories, locations, and behaviour. This project asks how quantum effects can persist at large scales (through zero-point motion, tunnelling, entanglement, superconductivity, and other “macroscopic quantum” phenomena) and how classical behaviour emerges in limits such as large mass or large numbers of particles.

The project will  bring together physics, chemistry, philosophy, history of science, and translation studies to compare concrete case studies across disciplines and to clarify what scientists and non-scientists mean when they use words like “object”, “classical”, “wave”, or “particle”. Alongside lectures, seminars, and workshops, the project leads will produce short, accessible digital resources (recordings, brief explainer videos, and a living glossary) to broaden reach beyond Durham and support teaching and public understanding. The longer-term goal is to build sustained interdisciplinary capacity at Durham. 

Ambition:

The core project question
When does a quantum description yield the “objects” of the macroscopic world, and what does it take (conceptually, mathematically, historically, and linguistically) for that transition to be understood and communicated without distortion?

Motivation
Across physics, chemistry and (selectively) biology, we encounter systems that are macroscopic in some sense yet show unmistakably quantum signatures: zero‑point motion and tunnelling in heavy-particle dynamics; collective quantum phases in materials (e.g. superconductivity); entanglement and decoherence in open systems; and the emergence (or breakdown) of classical approximations in molecular and materials modelling. At the same time, discussion of these phenomena is routinely mediated by everyday language that can mislead, creating barriers to interdisciplinary work and to responsible public understanding.

Objectives

1. to build a shared, case‑study‑driven picture of macroscopic quantum behaviour with emphasis on massive degrees of freedom (large mass / large N) and their quantum signatures (zero‑point motion, tunnelling), while treating entanglement as an important common thread that increasingly appears in new probes and technologies.
2. to clarify questions that connect disciplines: how large‑N/large‑mass limits are modelled and tested; how effective classical descriptions emerge in open quantum systems; what counts as an “object”, “structure”, or “classical behaviour” in different scientific practices; and how language choices shape understanding and misunderstanding.
3. to produce tangible outputs: a portfolio of benchmark case studies, a glossary/translation guide, and a short agenda identifying tractable open problems suitable for follow‑on funding.

Term:

Epiphany 2028

Activities and Events:

Will be added in due course