Quantum mechanics is rich with paradoxes and contradictions. It describes a microscopic world in which particles exist in a superposition of states—being in multiple places and configurations all at once, defined mathematically by what physicists call a “wavefunction.” But this runs counter to our everyday experience of objects that are either here or there, never both at the same time.

Typically, physicists manage this conflict by arguing that, when a quantum system comes into contact with a measuring device or an experimental observer, the system’s wavefunction “collapses” into a single, definite state. Now, with support from the Foundational Questions Institute, FQxI, an international team of physicists has shown that a family of unconventional solutions to this measurement problem—called “quantum collapse models”—has far-reaching implications for the nature of time and for clock precision.

They published their results suggesting a new way to distinguish these rival models from standard quantum theory, in Physical Review Research, in November 2025.

A new unified theory connects two fundamental domains of modern quantum physics: It joins two opposite views of how a single exotic particle behaves in a many-body system, namely as a mobile or static impurity among a large number of fermions, a so-called Fermi sea.

This new theoretical framework was developed at the Institute for Theoretical Physics of Heidelberg University. It describes the emergence of what is known as quasiparticles and furnishes a connection between two different quantum states that, according to the Heidelberg researchers, will have far-reaching implications for current quantum matter experiments.

A team from UNIGE shows that it is possible to determine the state of a quantum system from indirect measurements when it is coupled to its environment.

What is the state of a quantum system? Answering this question is essential for exploiting quantum properties and developing new technologies. In practice, this characterization generally relies on direct measurements, which require extremely well-controlled systems, as their sensitivity to external disturbances can distort the results. This constraint limits their applicability to specific experimental contexts.

A team from the University of Geneva (UNIGE) presents an alternative approach, tailored to open quantum systems, in which the interaction with the environment is turned into an advantage rather than an obstacle. Published in Physical Review Letters —with the “Editor’s Suggestion” label—this work brings quantum technologies a step closer to real-world conditions.

Electrons are usually described as particles, but in a rare quantum material, that picture completely breaks down

Quantum materials can behave in surprising ways when many tiny spins act together, producing effects that don’t exist in single particles.

Collective behavior is an unusual phenomenon in condensed-matter physics. When quantum spins interact together as a system, they produce unique effects not seen in individual particles. Understanding how quantum spins interact to produce this behavior is central to modern condensed-matter physics.

Among these phenomena, the Kondo effect—the interaction between localized spins and conduction electrons—plays a central role in many quantum phenomena.

Yet in real materials, the presence of additional charges and orbital degrees of freedom make it difficult to isolate the essential quantum mechanism behind the Kondo effect. In these materials, electrons don’t just have spin, they also move around and can occupy different orbitals. When all these extra behaviors mix together, it becomes hard to focus only on the spin interactions responsible for the Kondo effect.