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Quantum technologies

Dieter Meschede's research group
Home Group members Manolo Rivera Lam
Group members
MSc. Manolo Rivera Lam
Position: PhD student
Field of research: Few-atom quantum systems
Office room: 224
E-mail: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it.
Office: +49 228 73-3128


  • G. Ness, M. R. Lam, W. Alt, D. Meschede, Y. Sagi and A. Alberti
    Observing quantum-speed-limit crossover with matter wave interferometry, arXiv:2104.05638 [quant-ph], (2021)arXivBibTeXPDF

    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 (MT) and the Margolus–Levitin (ML) 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 MT limit constrains the evolution at all times, and a second where a crossover to the ML 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.

  • M. R. Lam, N. Peter, T. Groh, W. Alt, C. Robens, D. Meschede, A. Negretti, S. Montangero, T. Calarco and A. Alberti
    Demonstration of quantum brachistochrones between distant states of an atom, Phys. Rev. X (Featured in Physics) 11, 011035 (2021)arXivBibTeXPDF

    Transforming an initial quantum state into a target state through the fastest possible route—a quantum brachistochrone—is a fundamental challenge for many technologies based on quantum mechanics. Here, we demonstrate fast coherent transport of an atomic wave packet over a distance of 15 times its size—a paradigmatic case of quantum processes where the target state cannot be reached through a local transformation. Our measurements of the transport fidelity reveal the existence of a minimum duration—a quantum speed limit—for the coherent splitting and recombination of matter waves. We obtain physical insight into this limit by relying on a geometric interpretation of quantum state dynamics. These results shed light upon a fundamental limit of quantum state dynamics and are expected to find relevant applications in quantum sensing and quantum computing.

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