Quantum 2025 – wissenschaftliches Programm
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TUE: Tuesday Contributed Sessions
TUE 10: Foundational / Mathematical Aspects – Rigorous Results
TUE 10.8: Vortrag
Dienstag, 9. September 2025, 16:00–16:15, ZHG103
Quantum Incompatibility in Parallel vs Antiparallel Spins — Ram K Patra1, •Kunika Agarwal1, Biswajit Paul2, Snehasish R Chowdhury1, Sahil G Naik1, and Manik Banik1 — 1Department of Physics of Complex Systems, S. N. Bose National Center for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India — 2Department of Mathematics, Balagarh Bijoy Krishna Mahavidyalaya, Balagarh, Hooghly-712501, West Bengal, India
We investigate the joint measurability of incompatible quantum observables on ensembles of parallel and antiparallel spin pairs. In parallel configuration, two systems are identically prepared, whereas in antiparallel configuration each system is paired with its spin-flipped counterpart. We demonstrate that the antiparallel configuration enables exact simultaneous prediction of three mutually orthogonal spin components*an advantage unattainable in the parallel case. As we show, this enhanced measurement compatibility in antiparallel configuration is better explained within the framework of generalized probabilistic theories, which allow a broader class of composite structures while preserving quantum descriptions at the subsystem level. Furthermore, this approach extends the study of measurement incompatibility to more general configurations beyond just the parallel and antiparallel cases, providing deeper insights into the boundary between physical and unphysical quantum state evolutions. To this end, we discuss how the enhanced measurement compatibility in antiparallel configuration can be observed on a finite ensemble of qubit states, paving the way for an experimental demonstration of this advantage.
Keywords: Quantum Incompatibility; Elegant Joint Measurement; Parallel-Antiparallel spins; Quantum State Estimation