Introduction: Experimental and Theoretical Status of Decoherence

Philippe Blanchard, Erich Joos, Domenico Giulini +2 more

Philippe Blanchard

Matthew J. Brandsema

With the introduction of the quantum radar concept, there has been a great number of discoveries theoretically about its implementation and the possible benefits for use in remote sensing. As of this date, there has been little experimental realization to bolster the theoretical claims. This paper will provide a brief survey of the current status of a quantum radar implementation based on the more relevant research. It will be shown that all of the pieces are currently in place to provide simple, proof-of-concept type of quantum radar experiments.

A. A. Tomaz, Rafael Souza Mattos, Mario Barbatti

Left on its own, a quantum state evolves deterministically under the Schrödinger equation, forming superpositions. Upon measurement, however, a stochastic process governed by the Born rule collapses it to a single outcome. This dual evolution of quantum states – the core of the Measurement Problem – has puzzled physicists and philosophers for nearly a century. Yet, amid the cacophony of competing interpretations, the problem today is not as impenetrable as it once seemed. This paper reviews the current status of the Measurement Problem, distinguishing between what is well understood and what remains unresolved. We examine key theoretical approaches, including decoherence, many-worlds interpretation, objective collapse theories, hidden-variable theories, dualistic approaches, deterministic models, and epistemic interpretations. To make these discussions accessible to a broader audience, we also reference curated online resources that provide high-quality introductions to central concepts.

Round Table, Hervé Zwirn C

Gwyn Williams

Following a brief introduction to spin-glass systems, the current status of experimental evidence on the occurrence of a phase transition is reviewed. Recent analyses of dynamical properties of spin glasses are discussed in terms of several model predictions, including the conclusion of a divergent relaxation time τ at a finite temperature, although with large, non-mean-field indices z and v. The role of regular terms (leading to corrections to scaling) in the nonlinear response are reviewed, stressing their influence on the evaluation of the susceptibility and order-parameter exponents γ′ and β′.