An international team of scientists has taken a closer look at how memory works in quantum systems and uncovered a surprising result. Their research shows that a quantum process can seem completely memoryless when viewed one way, yet still retain memory when examined from another angle. This unexpected finding opens the door to new lines of research in quantum science and technology.
In classical physics, the idea of memory is straightforward. A system is considered memoryless if its future behavior depends only on its current state. If past states continue to influence what happens next, the system is said to have memory.
Quantum physics is far less clear-cut. Quantum systems can store and transfer information in ways that have no classical counterpart, and measurements themselves play a key role in how these systems evolve. Because of this, defining memory in quantum mechanics has remained a challenge.
In a study published in PRX Quantum, researchers from the University of Turku in Finland, the University of Milan in Italy, and Nicolaus Copernicus University in ToruĊ in Poland revisited the concept of memory in quantum systems to better understand its meaning.
"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," says first author, Doctoral Researcher Federico Settimo from the University of Turku.
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