Quantum Foundations
Our group investigates a wide array of these foundational topics using table-top photonic experiments. Our research spans topics from quantum thermodynamics to the development of new techniques to generate and characterize complex entangled states.
A central theme of our work involves challenging classical intuitions, such as the assumption that events must occur in a well-defined sequence: quantum mechanics allows events to occur in superposition in a so-called “indefinite causal order.” This work not only probes the limits of quantum correlations but also offers potential advantages for quantum information processing.
As quantum systems grow in complexity, extracting information from them efficiently becomes a monumental challenge that also touches on foundational concepts such as the information content of a single quantum state and quantum measurements. We study different aspects of this topic, developing practical protocols for quantum state certification and implementing novel quantum measurements to extract information without collapsing the quantum state.
Selected Publications
Time-Delocalized Local Measurements in an Indefinite Causal Order.
Y. Valibouse, M. Cladera-Rosselló, M. Antesberger, P. Lima, P. Walther, L. A Rozema, arXiv:2604.11878 (2026).
Testing single-photon entanglement using self-referential measurements
D. Kun, T. Strömberg, B. Dakic, P. Walther, L. A. Rozema, Optica 13, 745-751 (2026).
Toward an Experimental Device-Independent Verification of Indefinite Causal Order
C. M.D. Richter, M. Antesberger, H. Cao, P. Walther, L. A. Rozema, PRX Quantum 7, 010354 (2026).
Experimental quantum state certification by actively sampling photonic entangeld states
M. Antesberger, M. M. E. Schmid, H. Cao, B. Dakic, L. A. Rozema, P. Walther, Science Advances 12, 7 (2026).
Experimental aspects of indefinite caussal order in quantum mechanics
L. A. Rozema, T. Strömberg, H. Cao, B.- H. Liu, P. Walther, Nature Review Physics 6, 483 (2024).
Enhanced Photonic Maxwell's Demon with Correlated Baths
G. L. Zanin, M. Antesberger, M. J. Jaquet, P. H. Souto Ribeiro, L. A. Rozema, P. Walther, Quantum 6, 810 (2022).
Experimental few-copy multipartite entanglement detection
V. Saggio, A. Dimić, C. Greganti, L. A. Rozema, P. Walther, B. Dakić, Nature Physics 15, 935–940 (2019).
Experimental Superposition of Orders of Quantum Gates
L.M. Procopio et al.,Nature Communications 6, 7913 (2015)
