An international team of researchers has discovered that quantum systems can appear memoryless from one viewpoint while retaining memory from another. The finding, based on Schrödinger and Heisenberg pictures, reveals hidden memory effects in quantum dynamics. This could impact the design of quantum technologies.
Scientists from the University of Turku in Finland, the University of Milan in Italy, and Nicolaus Copernicus University in Toruń in Poland have uncovered that quantum systems can seem to remember and forget their past simultaneously, depending on the observation method. Their study, published in PRX Quantum, shows that memory in quantum processes manifests differently when viewed through evolving quantum states or measurable observables, as first detailed by researchers including Federico Settimo, Andrea Smirne, Kimmo Luoma, Bassano Vacchini, Jyrki Piilo, and Dariusz Chruściński. Materials for the research were provided by the University of Turku. Federico Settimo, a doctoral researcher at the University of Turku and the study's first author, explained: 'Our work shows that memory is not a single concept but can manifest in different ways depending on how the evolution of a system is described.' This challenges classical notions where memoryless systems depend solely on current states, highlighting quantum mechanics' unique information storage. The team found memory effects visible in one framework but hidden in the other, suggesting quantum memory is more complex than previously thought. Professor Jyrki Piilo of theoretical physics at the University of Turku noted: 'Our findings open up new research avenues into the dynamics of quantum systems. Moreover, our work has implications beyond its foundational significance for quantum technologies, where the external environment induces noise and memory effects.' These insights could help develop strategies to mitigate noise or exploit environmental effects in quantum devices, reshaping foundational quantum concepts.