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Your search keyword '"Werner, Albert H."' showing total 6 results
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6 results on '"Werner, Albert H."'

1. Exponential tail estimates for quantum lattice dynamics

Author

Cedzich, Christopher, Joye, Alain, Werner, Albert H., and Werner, Reinhard F.

Subjects
Quantum Physics, Mathematical Physics
Abstract

We consider the quantum dynamics of a particle on a lattice for large times. Assuming translation invariance, and either discrete or continuous time parameter, the distribution of the ballistically scaled position $Q(t)/t$ converges weakly to a distribution that is compactly supported in velocity space, essentially the distribution of group velocity in the initial state. We show that the total probability of velocities strictly outside the support of the asymptotic measure goes to zero exponentially with $t$, and we provide a simple method to estimate the exponential rate uniformly in the initial state. Near the boundary of the allowed region the rate function goes to zero like the power 3/2 of the distance to the boundary. The method is illustrated in several examples., Comment: 20 pages, 6 figures

Published
2024

2. Efficient and robust estimation of many-qubit Hamiltonians

Author

Stilck França, Daniel (author), Markovich, L. (author), Dobrovitski, V.V. (author), Werner, Albert H. (author), Borregaard, J. (author), Stilck França, Daniel (author), Markovich, L. (author), Dobrovitski, V.V. (author), Werner, Albert H. (author), and Borregaard, J. (author)

Abstract

Characterizing the interactions and dynamics of quantum mechanical systems is an essential task in developing quantum technologies. We propose an efficient protocol based on the estimation of the time-derivatives of few qubit observables using polynomial interpolation for characterizing the underlying Hamiltonian dynamics and Markovian noise of a multi-qubit device. For finite range dynamics, our protocol exponentially relaxes the necessary time-resolution of the measurements and quadratically reduces the overall sample complexity compared to previous approaches. Furthermore, we show that our protocol can characterize the dynamics of systems with algebraically decaying interactions. The implementation of the protocol requires only the preparation of product states and single-qubit measurements. Furthermore, we improve a shadow tomography method for quantum channels that is of independent interest and discuss the robustness of the protocol to various errors. This protocol can be used to parallelize the learning of the Hamiltonian, rendering it applicable for the characterization of both current and future quantum devices., QID/Borregaard Group, QID/Dobrovitski Group, QN/Borregaard groep

Published
2024
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3. Efficient and robust estimation of many-qubit Hamiltonians

Author

Stilck França, Daniel, Markovich, Liubov A., Dobrovitski, V. V., Werner, Albert H., Borregaard, Johannes, Stilck França, Daniel, Markovich, Liubov A., Dobrovitski, V. V., Werner, Albert H., and Borregaard, Johannes

Abstract

Characterizing the interactions and dynamics of quantum mechanical systems is an essential task in developing quantum technologies. We propose an efficient protocol based on the estimation of the time-derivatives of few qubit observables using polynomial interpolation for characterizing the underlying Hamiltonian dynamics and Markovian noise of a multi-qubit device. For finite range dynamics, our protocol exponentially relaxes the necessary time-resolution of the measurements and quadratically reduces the overall sample complexity compared to previous approaches. Furthermore, we show that our protocol can characterize the dynamics of systems with algebraically decaying interactions. The implementation of the protocol requires only the preparation of product states and single-qubit measurements. Furthermore, we improve a shadow tomography method for quantum channels that is of independent interest and discuss the robustness of the protocol to various errors. This protocol can be used to parallelize the learning of the Hamiltonian, rendering it applicable for the characterization of both current and future quantum devices. © 2024, The Author(s).

Published
2024

4. Going beyond gadgets: the importance of scalability for analogue quantum simulators.

Author

Harley, Dylan, Datta, Ishaun, Klausen, Frederik Ravn, Bluhm, Andreas, França, Daniel Stilck, Werner, Albert H., and Christandl, Matthias

Subjects
COMPLEXITY (Philosophy), SCALABILITY, IMPLEMENTS, utensils, etc., PHYSICS, HARDWARE
Abstract

Quantum hardware has the potential to efficiently solve computationally difficult problems in physics and chemistry to reap enormous practical rewards. Analogue quantum simulation accomplishes this by using the dynamics of a controlled many-body system to mimic those of another system; such a method is feasible on near-term devices. We show that previous theoretical approaches to analogue quantum simulation suffer from fundamental barriers which prohibit scalable experimental implementation. By introducing a new mathematical framework and going beyond the usual toolbox of Hamiltonian complexity theory with an additional resource of engineered dissipation, we show that these barriers can be overcome. This provides a powerful new perspective for the rigorous study of analogue quantum simulators. Analogue quantum simulation has looser experimental requirements than its digital counterpart, but rigorous theoretical results on the capabilities of realisable experiments are scarce. Here, the authors fill this gap by proposing an alternative mathematical framework, and showing how to overcome barriers to scalable implementations using additional resources such as engineered dissipation. [ABSTRACT FROM AUTHOR]

Published
2024
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