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arXiv · 2104.05638

Observing crossover between quantum speed limits

Gal Ness·Manolo R. Lam·Wolfgang Alt·Dieter Meschede·Yoav Sagi·Andrea Alberti
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Abstract

Quantum mechanics sets fundamental limits on how fast quantum states can be transformed in time. Two well-known quantum speed limits are the Mandelstam-Tamm and the Margolus-Levitin bounds, which relate the maximum speed of evolution to the system's energy uncertainty and mean energy, respectively. Here, we test concurrently both limits in a multi-level system by following the motion of a single atom in an optical trap using fast matter wave interferometry. Our data reveal two different regimes: one where the Mandelstam-Tamm limit constrains the evolution at all times, and a second where a crossover to the Margolus-Levitin limit is manifested at longer times. We take a geometric approach to quantify the deviation from the speed limit, measuring how much the matter wave's quantum evolution deviates from the geodesic path in the Hilbert space of the multi-level system. Our results, establishing quantum speed limits beyond the simple two-level system, are important to understand the ultimate performance of quantum computing devices and related advanced quantum technologies.

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Gal Ness, Manolo R. Lam, Wolfgang Alt, Dieter Meschede, Yoav Sagi, Andrea Alberti. 2021-10-19. Observing crossover between quantum speed limits. https://doi.org/10.1126/sciadv.abj9119

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