Aktuellste Preprints
Observing the quantum Mpemba effect in quantum simulations
arXiv:2401.04270
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The non-equilibrium physics of many-body quantum systems harbors various unconventional phenomena. In this study, we experimentally investigate one of the most puzzling of these phenomena— the quantum Mpemba effect, where a tilted ferromagnet restores its symmetry more rapidly when it is farther from the symmetric state compared to when it is closer. We present the first experimental evidence of the occurrence of this effect in a trapped-ion quantum simulator. The symmetry breaking and restoration are monitored through entanglement asymmetry, probed via randomized measurements, and post-processed using the classical shadows technique. Our findings are further substantiated by measuring the Frobenius distance between the experimental state and the stationary thermal symmetric theoretical state, offering direct evidence of subsystem thermalization.
Motional state analysis of a trapped ion by ultra-narrowband composite pulses
arXiv:2402.10041
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In this work, we present a method for measuring the motional state of a two-level system coupled to
a harmonic oscillator. Our technique uses ultra-narrowband composite pulses on the blue sideband
transition to scan through the populations of the different motional states. Our approach does
not assume any previous knowledge of the motional state distribution and is easily implemented.
It is applicable both inside and outside of the Lamb-Dicke regime. For higher phonon numbers
especially, the composite pulse sequence can be used as a filter for measuring phonon number
ranges. We demonstrate this measurement technique using a single trapped ion and show good
detection results with the numerically evaluated pulse sequence.
Floquet Flux Attachment in Cold Atomic Systems
arXiv:2401.08754
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Flux attachment provides a powerful conceptual framework for understanding certain forms of topological order, including most notably the fractional quantum Hall effect. Despite its ubiquitous use as a theoretical tool, directly realizing flux attachment in a microscopic setting remains an open challenge. Here, we propose a simple approach to realizing flux attachment in a periodically-driven (Floquet) system of either spins or hard-core bosons. We demonstrate that such a system naturally realizes correlated hopping interactions and provides a sharp connection between such interactions and flux attachment. Starting with a simple, nearest-neighbor, free boson model, we find evidence -- from both a coupled wire analysis and large-scale density matrix renormalization group simulations -- that Floquet flux attachment stabilizes the bosonic integer quantum Hall state at 1/4 filling (on a square lattice), and the Halperin-221 fractional quantum Hall state at 1/6 filling (on a honeycomb lattice). At 1/2 filling on the square lattice, time-reversal symmetry is instead spontaneously broken and bosonic integer quantum Hall states with opposite Hall conductances are degenerate. Finally, we propose an optical-lattice-based implementation of our model on a square lattice and discuss prospects for adiabatic preparation as well as effects of Floquet heating.
Hamilton-Jacobi-Bellman equations for Rydberg-blockade processes
arXiv:2402.12956
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We discuss time-optimal control problems for two setups involving globally driven Rydberg atoms in the blockade limit by deriving the associated Hamilton-Jacobi-Bellman equations. From these equations, we extract the globally optimal trajectories and the corresponding controls for several target processes of the atomic system, using a generalized method of characteristics. We apply this method to retrieve known results for CZ and C-phase gates, and to find new optimal pulses for all elementary processes involved in the universal quantum computation scheme introduced in [Physical Review Letters 131, 170601 (2023)].
State Expansion of a Levitated Nanoparticle in a Dark Harmonic Potential
arXiv:2312.13111
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