Michael Kästner
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View article: Long-range Kitaev chain in a thermal bath: analytic techniques for time-dependent systems and environments
Long-range Kitaev chain in a thermal bath: analytic techniques for time-dependent systems and environments Open
We construct and solve a “minimal model” with which nonequilibrium phenomena in many-body open quantum systems can be studied analytically under time-dependent parameter changes in the system and/or the bath. Coupling a suitable configurat…
View article: Long-range systems, (non)extensivity, and the rescaling of energies
Long-range systems, (non)extensivity, and the rescaling of energies Open
Systems with long-range interactions have seen a surge of interest in the past decades. In the wake of this surge, the use of a system size dependent rescaling, sometimes termed "Kac prescription," of the long-range pair potential has seen…
View article: Ancilla-free measurement of out-of-time-ordered correlation functions: General measurement protocol and Rydberg atom implementation
Ancilla-free measurement of out-of-time-ordered correlation functions: General measurement protocol and Rydberg atom implementation Open
We introduce a protocol that gives access to out-of-time-ordered correlation functions in many-body quantum systems. Unlike other such protocols, our proposal, which can be applied to arbitrary initial states, neither requires ancilla degr…
View article: Universal cooling dynamics toward a quantum critical point
Universal cooling dynamics toward a quantum critical point Open
We investigate the loss of adiabaticity when cooling a many-body quantum system from an initial thermal state toward a quantum critical point. The excitation density, which quantifies the degree of adiabaticity of the dynamics, is found to…
View article: Long-range Kitaev chain in a thermal bath: Analytic techniques for time-dependent systems and environments
Long-range Kitaev chain in a thermal bath: Analytic techniques for time-dependent systems and environments Open
We construct and solve a "minimal model" with which nonequilibrium phenomena in many-body open quantum systems can be studied analytically under time-dependent parameter changes in the system and/or the bath. Coupling a suitable configurat…
View article: Robust control of quantum systems by quantum systems
Robust control of quantum systems by quantum systems Open
Quantum systems can be controlled by other quantum systems in a reversible way, without any information leaking to the outside of the system-controller compound. Such coherent quantum control is deterministic, is less noisy than measuremen…
View article: Integrable active atom interferometry
Integrable active atom interferometry Open
Active interferometers are designed to enhance phase sensitivity beyond the standard quantum limit by generating entanglement inside the interferometer. An atomic version of such a device can be constructed by means of a spinor Bose–Einste…
View article: Bosonic representation of a Lipkin-Meshkov-Glick model with Markovian dissipation
Bosonic representation of a Lipkin-Meshkov-Glick model with Markovian dissipation Open
We study the dynamics of a Lipkin-Meshkov-Glick model in the presence of\nMarkovian dissipation, with a focus on late-time dynamics and the approach to\nthermal equilibrium. Making use of a vectorized bosonic representation of the\ncorresp…
View article: Ancilla-assisted probing of temporal quantum correlations of large spins
Ancilla-assisted probing of temporal quantum correlations of large spins Open
When measuring quantum spins at two or more different times, the later measurements are affected by measurement backaction occurring due to the earlier measurements. This makes the measurement of temporal quantum correlation functions chal…
View article: Thermalization of a Lipkin-Meshkov-Glick model coupled to a bosonic bath
Thermalization of a Lipkin-Meshkov-Glick model coupled to a bosonic bath Open
CITATION: Louw, J. C., Kriel, J. N & Kastner, M. 2019. Thermalization of a Lipkin-Meshkov-Glick model coupled to a bosonic bath. Physical Review A, 100(2):022115, doi:10.1103/PhysRevA.100.022115.
View article: Quantum kinetic perturbation theory for near-integrable spin chains with weak long-range interactions
Quantum kinetic perturbation theory for near-integrable spin chains with weak long-range interactions Open
For a transverse-field Ising chain with weak long-range interactions we develop a perturbative scheme, based on quantum kinetic equations, around the integrable nearest-neighbour model. We introduce, discuss, and benchmark several truncati…
View article: Classical Lieb-Robinson Bound for Estimating Equilibration Timescales of Isolated Quantum Systems
Classical Lieb-Robinson Bound for Estimating Equilibration Timescales of Isolated Quantum Systems Open
We study equilibration of an isolated quantum system by mapping it onto a network of classical oscillators in Hilbert space. By choosing a suitable basis for this mapping, the degree of locality of the quantum system reflects in the sparse…
View article: Quantum kinetic perturbation theory for near-integrable spin chains with\n weak long-range interactions
Quantum kinetic perturbation theory for near-integrable spin chains with\n weak long-range interactions Open
For a transverse-field Ising chain with weak long-range interactions we\ndevelop a perturbative scheme, based on quantum kinetic equations, around the\nintegrable nearest-neighbour model. We introduce, discuss, and benchmark\nseveral trunc…
View article: Lieb–Robinson bounds for open quantum systems with long-ranged interactions
Lieb–Robinson bounds for open quantum systems with long-ranged interactions Open
We state and prove four types of Lieb–Robinson bounds valid for many-body open quantum systems with power law decaying interactions undergoing out of equilibrium dynamics. We also provide an introductory and self-contained discussion of th…
View article: Dynamical Critical Scaling of Long-Range Interacting Quantum Magnets
Dynamical Critical Scaling of Long-Range Interacting Quantum Magnets Open
Slow quenches of the magnetic field across the paramagnetic-ferromagnetic phase transition of spin systems produce heat. In systems with short-range interactions the heat exhibits universal power-law scaling as a function of the quench rat…
View article: Quenches near criticality of the quantum Ising chain—power and limitations of the discrete truncated Wigner approximation
Quenches near criticality of the quantum Ising chain—power and limitations of the discrete truncated Wigner approximation Open
The semi-classical discrete truncated Wigner approximation (dTWA) has\nrecently been proposed as a simulation method for spin-$1/2$ systems. While it\nappears to provide a powerful approach which shows promising results in higher\ndimensio…
View article: Noninvasive measurement of dynamic correlation functions
Noninvasive measurement of dynamic correlation functions Open
CITATION: Uhrich, P., et al. 2017. Noninvasive measurement of dynamic correlation functions. Physical Review A, 96(2):022127, doi:10.1103/PhysRevA.96.022127.
View article: Universal equilibrium scaling functions at short times after a quench
Universal equilibrium scaling functions at short times after a quench Open
By analyzing spin-spin correlation functions at relatively short distances, we show that equilibrium near-critical properties can be extracted at short times after quenches into the vicinity of a quantum critical point. The time scales aft…
View article: Subexponential phase space and nonconcentrating distributions in a constrained spin model
Subexponential phase space and nonconcentrating distributions in a constrained spin model Open
Motivated by recent experiments with two-component Bose--Einstein condensates, we study fully-connected spin models subject to an additional constraint. The constraint is responsible for the Hilbert space dimension to scale only linearly w…
View article: Quantum effects in the cooperative scattering of light by atomic clouds
Quantum effects in the cooperative scattering of light by atomic clouds Open
Scattering of classical light by atomic clouds induces photon-mediated\neffective long-range interactions between the atoms and leads to cooperative\neffects even at low atomic densities. We introduce a novel simulation technique\nthat all…
View article: Prethermalization and persistent order in the absence of a thermal phase transition
Prethermalization and persistent order in the absence of a thermal phase transition Open
CITATION: Halimeh, J. C., et al. 2017. Prethermalization and persistent order in the absence of a thermal phase transition. Physical Review B, 95(2):1-7, doi:10.1103/PhysRevB.95.024302.
View article: Simulation of quantum spin dynamics by phase space sampling of Bogoliubov-Born-Green-Kirkwood-Yvon trajectories
Simulation of quantum spin dynamics by phase space sampling of Bogoliubov-Born-Green-Kirkwood-Yvon trajectories Open
A numerical method, suitable for the simulation of the time evolution of\nquantum spin models of arbitrary lattice dimension, is presented. The method\ncombines sampling of the Wigner function with evolution equations obtained from\nthe Bo…
View article: Entanglement-enhanced spreading of correlations
Entanglement-enhanced spreading of correlations Open
CITATION: Kastner, M. 2015. Entanglement-enhanced spreading of correlations. New Journal of Physics, 17:123024, doi:10.1088/1367-2630/17/12/123024.
View article: Interplay of soundcone and supersonic propagation in lattice models with power law interactions
Interplay of soundcone and supersonic propagation in lattice models with power law interactions Open
CITATION: Storch, D-M., Van den Worm, M. & Kastner, M. 2015. Interplay of soundcone and supersonic propagation in lattice models with power law interactions. New Journal of Physics, 17:063021, doi:10.1088/1367-2630/17/6/063021.