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Fluctuations in Light-Matter Interactions: Emerging Quantum and Thermal Regimes

Mauro Antezza

Published Sep 24, 2026• 0 citations
OpenAlex

Abstract

Quantum and thermal electromagnetic fluctuations give rise to macroscopic phenomena such as Casimir–Lifshitz forces and radiative heat transfer. In this colloquium, I will introduce the common theoretical framework underlying these effects and discuss how they can be shaped and controlled through geometry, material properties, and nonequilibrium conditions. I will first discuss the giant Casimir torque arising between rotated metallic gratings, where a geometric transition at zero relative angle produces an anomalous torque enhancement and points toward the realization of a contactless quantum-vacuum torsional spring. I will then present a Kapitza-like mechanism for near-field radiative heat transfer, showing how rapid modulation of the vacuum gap or of the material response can alter the time-averaged thermal dynamics, shift stationary temperatures, and can stabilize or destabilize thermal steady states. Together, these examples illustrate emerging strategies for controlling mechanical forces and heat transport through shaping light–matter interactions.

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Quantum and thermal electromagnetic fluctuations give rise to macroscopic phenomena such as Casimir–Lifshitz forces and radiative heat transfer. In this colloquium, I will introduce the common theoretical framework underlying these effects and discuss how they can be shaped and controlled through geometry, material properties, and nonequilibrium conditions. I will first discuss the giant Casimir torque arising between rotated metallic gratings, where a geometric transition at zero relative angle produces an anomalous torque enhancement and points toward the realization of a contactless quantum-vacuum torsional spring. I will then present a Kapitza-like mechanism for near-field radiative heat transfer, showing how rapid modulation of the vacuum gap or of the material response can alter the time-averaged thermal dynamics, shift stationary temperatures, and can stabilize or destabilize thermal steady states. Together, these examples illustrate emerging strategies for controlling mechanical forces and heat transport through shaping light–matter interactions.
We will discuss the behavior of one or more elementary quantum system (atom, molecules, quantum dot, …) interacting with a stationary, simple and rich electromagnetic environment out of thermal equilibrium: The electromagnetic field is produced by a simple configuration of macroscopic objects held at thermal equilibrium at different temperatures. We will show how the internal atomic dynamics can be deeply affected by the non equilibrium configuration leading to unexpected phenomena like a spontaneous inversion of population, new cooling mechanisms obtained by heating the system, and the possibility to create and protect entanglement in a stationary and robust way. Finally, we will discuss how this system may directly allow the realization of atomic quantum thermal machines, with high efficiency and a genuine quantum behavior.
Coupling between quantum emitters and modes of light is foundational to studies of quantum systems. Coherent interactions between matter and light have greatly advanced the development of quantum technologies. When an ensemble of atoms interacts with light that is confined within a cavity---a resonator for photons---light also mediates atom-atom interactions, leading to collective phenomena that cannot be extrapolated from microscopic behaviors. Understanding how interactions among quantum particles lead to macroscopic phenomena, such as phase transitions and breaking of symmetries, remains a challenge in modern physics. In this dissertation, I present results addressing this challenge in the context of mesoscopic arrays of optical-tweezer-trapped atoms interfaced with a high-finesse optical cavity. In particular, the physics we investigate arises from the collective scattering of light. Utilizing the ability to place atoms with nanometer-scale precision, we engineer superradiant and subradiant states, where control over interference of the emission from multiple atoms leads to collectively enhanced or suppressed amounts of scattered light. Building on this work, we investigate the emergence of optomechanical self-organization, mediated by superradiance in the cavity electromagnetic field. By coupling atoms to the same cavity mode, the atoms exert forces on one another through the exchange of photons, leading them to autonomously order themselves spatially. We characterize mesoscopic fluctuations and their effect on symmetry-breaking dynamics associated with self-organization. Finally, we extend this framework to theoretically investigate how the phase of the atom-cavity coupling can be altered to generate higher symmetries. Our analysis reveals first-order phase transitions and instabilities induced by non-reciprocal forces. Altogether, this work establishes a path towards realizing mesoscopic systems of complex phases of matter in cavity quantum electrodynamics with unprecedented programmability.
We describe a contactless heat engine in which quantum and thermal electromagnetic fluctuations act as the working medium. The setup consists of two concentric cylinders held at different temperatures. The inner cylinder stably levitates within the outer one due to repulsive nonequilibrium Casimir forces. The chirality of the setup is broken by using nonreciprocal dielectric materials, akin to application of a magnetic field along the common cylinder axis. Using Rytov fluctuational electrodynamics, we show that heat transfer and torque can be expressed in terms of an angular-momentum-resolved heat flux density, Φn(ω)Φ_n(ω)Φn​(ω): each exchanged photon carries energy ℏω\hbar ωℏω and angular momentum ℏn\hbar nℏn. In reciprocal media contributions from modes nnn and −n-n−n cancel and there is no net torque; nonreciprocity breaks this symmetry and powers rotation of the inner cylinder. Even in the absence of contact, electromagnetic fluctuations produce a frictional torque opposing rotation that we compute. This enables computation of characteristic steady state rotations, and estimation of the engine efficiency (which remains bounded by the Carnot limit). The cylindrical setup provides a natural realization of fluctuation-induced angular-momentum transfer and a possible route toward nanoscale contactless engines.
Coupling tailored electromagnetic fluctuations to materials provides a resource for controlling correlated quantum matter. By structuring the frequency, spatial, and modal distribution of fluctuations through a new generation of cavity quantum materials, vacuum and thermal spectra can shift phase boundaries and stabilize or suppress orders. This review organizes the field around a fluctuation-focused perspective, surveying a practical design toolbox and recent milestones, and outlining theory-experiment challenges in realistic, multimode, beyond-long-wavelength regimes. We highlight photonic observables and map opportunities for equilibrium and driven control across superconducting, magnetic, moire, and topological platforms.
We propose to use a rotating corrugated material plate in order to stir, through the Casimir-Polder interaction, quantized vortices in an harmonically trapped Bose-Einstein condensate. The emergence of such vortices within the condensate cannot be explained with a computation of the Casimir-Polder potential based on the pairwise summation approach or on the proximity force approximation. It thus appears as a genuine signature of non-trivial geometry effects on the electromagnetic vacuum fluctuations, which fully exploits the superfluid nature of the sample. In order to discuss quantitatively the generation of Casimir-driven vortices, we derive an exact non-perturbative theory of the Casimir-Polder potential felt by the atoms in front of the grating. Our numerical results for a Rb condensate close to a Si grating show that the resulting quantum vacuum torque is strong enough to provide a contactless transfer of angular momentum to the condensate and generate quantized vortices under realistic experimental conditions at separation distances around 3 μm.