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See detailVariational principle for optimal quantum controls in quantum metrology
Yang, Jing UL; Pang, Shengshi; Chen, Zekai et al

in Physical Review Letters (2022)

We develop a variational principle to determine the quantum controls and initial state that optimizes the quantum Fisher information, the quantity characterizing the precision in quantum metrology. When ... [more ▼]

We develop a variational principle to determine the quantum controls and initial state that optimizes the quantum Fisher information, the quantity characterizing the precision in quantum metrology. When the set of available controls is limited, the exact optimal initial state and the optimal controls are, in general, dependent on the probe time, a feature missing in the unrestricted case. Yet, for time-independent Hamiltonians with restricted controls, the problem can be approximately reduced to the unconstrained case via Floquet engineering. In particular, we find for magnetometry with a time-independent spin chain containing three-body interactions, even when the controls are restricted to one- and two-body interaction, that the Heisenberg scaling can still be approximately achieved. Our results open the door to investigate quantum metrology under a limited set of available controls, of relevance to many-body quantum metrology in realistic scenarios. [less ▲]

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See detailProbing Quantum Speed Limits with Ultracold Gases
Del Campo Echevarria, Adolfo UL

in Physical Review Letters (2021)

Quantum speed limits (QSLs) rule the minimum time for a quantum state to evolve into a distinguishable state in an arbitrary physical process. These fundamental results constrain a notion of distance ... [more ▼]

Quantum speed limits (QSLs) rule the minimum time for a quantum state to evolve into a distinguishable state in an arbitrary physical process. These fundamental results constrain a notion of distance traveled by the quantum state, known as the Bures angle, in terms of the speed of evolution set by nonadiabatic energy fluctuations. I theoretically propose how to measure QSLs in an ultracold quantum gas confined in a timedependent harmonic trap. In this highly-dimensional system of continuous variables, quantum tomography is prohibited. Yet, QSLs can be probed whenever the dynamics is self-similar by measuring as a function of time the cloud size of the ultracold gas. This makes it possible to determine the Bures angle and energy fluctuations, as I discuss for various ultracold atomic systems. [less ▲]

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See detailMagneto-optical activity in nonmagnetic hyperbolic nanoparticles
Kuttruff, Joel; Gabbani, Alessio; Petrucci, Gaia et al

in Physical Review Letters (2021), 127

Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity ... [more ▼]

Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity in non-magnetic hyperbolic nanoparticles. We demonstrate that the magneto-optical response is driven by fundamental electric and magnetic dipole modes induced by the hyperbolic dispersion. Magnetic circular dichroism experiments confirm the theoretical predictions and reveal tunable magneto-optical activity across the visible and near infrared spectral range. [less ▲]

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See detailDissipation-Time Uncertainty Relation
Falasco, Gianmaria UL; Esposito, Massimiliano UL

in Physical Review Letters (2020), 125(12), 120604

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See detailToward Understanding Complex Spin Textures in Nanoparticles by Magnetic Neutron Scattering
G. Vivas, Laura; Yanes, Rocio; Berkov, Dmitry et al

in Physical Review Letters (2020), 125

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See detailArchetypal Soft-Mode-Driven Antipolar Transition in Francisite Cu3Bi(SeO3)(2)O2Cl
Milesi-Brault, Cosme; Toulouse, Constance UL; Constable, Evan et al

in PHYSICAL REVIEW LETTERS (2020), 124(9), 097603-6

Model materials are precious test cases for elementary theories and provide building blocks for the understanding of more complex cases. Here, we describe the lattice dynamics of the structural phase ... [more ▼]

Model materials are precious test cases for elementary theories and provide building blocks for the understanding of more complex cases. Here, we describe the lattice dynamics of the structural phase transition in francisite Cu3Bi(SeO3)(2)O2Cl at 115 K and show that it provides a rare archetype of a transition driven by a soft antipolar phonon mode. In the high-symmetry phase at high temperatures, the soft mode is found at (0,0,0.5) at the Brillouin zone boundary and is measured by inelastic x-ray scattering and thermal diffuse scattering. In the low-symmetry phase, this soft-mode is folded back onto the center of the Brillouin zone as a result of the doubling of the unit cell, and appears as a fully symmetric mode that can be tracked by Raman spectroscopy. On both sides of the transition, the mode energy squared follows a linear behavior over a large temperature range. First-principles calculations reveal that, surprisingly, the flat phonon band calculated for the high-symmetry phase seems incompatible with the displacive character found experimentally. We discuss this unusual behavior in the context of an ideal Kittel model of an antiferroelectric transition. [less ▲]

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See detailArchetypal Soft-Mode-Driven Antipolar Transition in Francisite Cu3BiðSeO3Þ2O2Cl
Milesi-Brault, Cosme; Toulouse, Constance UL; Constable, Evan et al

in Physical Review Letters (2020)

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See detailEfficiency Fluctuations of Stochastic Machines Undergoing a Phase Transition
Vroylandt, Hadrien; Esposito, Massimiliano UL; Verley, Gatien

in Physical Review Letters (2020), 124(25), 250603

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See detailWork Statistics across a Quantum Phase Transition
Fei, Zhaoyu; Freitas, Nahuel; Cavina, Vasco UL et al

in Physical Review Letters (2020), 124(17), 170603

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See detailEntropy Production in Open Systems: The Predominant Role of Intraenvironment Correlations
Ptaszyński, Krzysztof; Esposito, Massimiliano UL

in PHYSICAL REVIEW LETTERS (2019)

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See detailGiant Electrophononic Response in PbTiO3 by Strain Engineering
Torres, Pol; Iñiguez, Jorge UL; Rurali, Riccardo

in PHYSICAL REVIEW LETTERS (2019), 123(18),

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See detailMono-to-multilayer transition in growing bacterial colonies
You, Zhihong; Pearce, Daniel J. G.; Sengupta, Anupam UL et al

in Physical Review Letters (2019), 123(17-25),

The transition from monolayers to multilayered structures in bacterial colonies is a fundamental step in biofilm development. Observed across different morphotypes and species, this transition is ... [more ▼]

The transition from monolayers to multilayered structures in bacterial colonies is a fundamental step in biofilm development. Observed across different morphotypes and species, this transition is triggered within freely growing bacterial microcolonies comprising a few hundred cells. Using a combination of numerical simulations and analytical modeling, here we demonstrate that this transition originates from the competition between growth-induced in-plane active stresses and vertical restoring forces, due to the cell-substrate interactions. Using a simple chainlike colony of laterally confined cells, we show that the transition sets when individual cells become unstable to rotations; thus it is localized and mechanically deterministic. Asynchronous cell division renders the process stochastic, so that all the critical parameters that control the onset of the transition are continuously distributed random variables. Here we demonstrate that the occurrence of the first division in the colony can be approximated as a Poisson process in the limit of large cell numbers. This allows us to approximately calculate the probability distribution function of the position and time associated with the first extrusion. The rate of such a Poisson process can be identified as the order parameter of the transition, thus highlighting its mixed deterministic-stochastic nature. [less ▲]

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See detailMechanical Resonances of Mobile Impurities in a One-Dimensional Quantum Fluid
Schmidt, Thomas UL; Dolcetto, Giacomo; Pedder, Christopher et al

in Physical Review Letters (2019), 123

We study a one-dimensional interacting quantum liquid hosting a pair of mobile impurities causing backscattering. We determine the effective retarded interaction between the two impurities mediated by the ... [more ▼]

We study a one-dimensional interacting quantum liquid hosting a pair of mobile impurities causing backscattering. We determine the effective retarded interaction between the two impurities mediated by the liquid. We show that for strong backscattering this interaction gives rise to resonances and antiresonances in the finite-frequency mobility of the impurity pair. At the antiresonances, the two impurities remain at rest even when driven by a (small) external force. At the resonances, their synchronous motion follows the external drive in phase and reaches maximum amplitude. Using a perturbative renormalization group analysis in quantum tunneling across the impurities, we study the range of validity of our model. We predict that these mechanical antiresonances are observable in experiments on ultracold atom gases confined to one dimension. [less ▲]

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See detailElectric-Field Control of Magnetization, Jahn-Teller Distortion, and Orbital Ordering in Ferroelectric Ferromagnets
Chen, Lan; Xu, Changsong; Tian, Haoye UL et al

in PHYSICAL REVIEW LETTERS (2019), 122(24),

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See detailFerroelectricity with Asymmetric Hysteresis in Metallic LiOsO3 Ultrathin Films
Lu, Jinlian; Chen, Gong; Luo, Wei et al

in PHYSICAL REVIEW LETTERS (2019), 122(22),

Detailed reference viewed: 42 (1 UL)