The group of quantum and nonlinear optics at the Joint Laboratory of Optics deals long-term with twin beams that became an important tool for quantum optics as they exhibit quantum correlations and entanglement. A. Aspect, J. Clauser, and A. Zeilinger were awarded 2022 Nobel prize for physics for experiments with entangled photons. Quantum correlations cause that the results of measurements of properties of paired photons are not independent but bound together at a distance with invisible ties unparalleled in classical physics. This is why we call the paired photons nonclassical light.

The Laser Speckle Laboratory in the Joint Laboratory of Optics has developed a non-invasive method for monitoring plants' responses to induced stress. Speckle is a phenomenon in which the matt (optically rough) surface of an object is illuminated by a coherent laser beam and the reflected light field shows a typical speckled pattern caused by interference of light reflected off different points of the object. The pattern of the reflected light field (speckle field) is sensitive to the object movements and deformations and thus allows the changes that the surface of the object undergoes to be precisely tracked. The speckle effect also arises when the laser beam passes through a translucent object.

The LHC accelerator at CERN does not collide just protons, but also heavy nuclei, e.g. lead. In such collisions, conditions close to those as shortly after the Bing Bang can be simulated. In an early Universe the matter was in the state of a hot quark-gluon plasma and the top quark, the heaviest of all quarks, constitutes a new unique probe to study this form of matter. Owing to its large mass, it is born in processes leading to the quark-gluon plasma, rather than in the medium itself. Comparing processes known from proton-proton collisions to those with heavy ions, it is possible to study their production mechanism and use them as a probe testing the development of dense strongly interacting matter.

All physical systems can be roughly divided onto two types. Namely, conservative or Hermitian systems, where the whole system energy is preserved, and non-conservative or non-Hermitian systems, where the energy can irreversibly flow between the system and its surrounding environment.