1,720,978 research outputs found
Floquet engineering of Lie algebraic quantum systems
No full textWe propose a "Floquet engineering" formalism to systematically design a periodic driving protocol in order to stroboscopically realize the desired system starting from a given static Hamiltonian. The formalism is applicable to interacting and noninteracting quantum systems which have an underlying closed Lie algebraic structure. Unlike previous attempts at Floquet engineering, our method produces the desired Floquet Hamiltonian at any driving frequency and is not restricted to the fast or slow driving regimes. The approach is based on Wei-Norman ansatz, which was originally proposed to construct a time-evolution operator for any arbitrary driving. Here, we apply this ansatz to the micromotion dynamics, defined within one period of the driving, and engineer the functional form and operators of the driving protocol by fixing the gauge of the micromotion. To illustrate our idea, we use a two-band system or the systems consisting of two sublattices as a testbed. Particularly, we focus on engineering the cross-stitched lattice model that has been a paradigmatic flat-band model.11Nsciescopu
Canonically consistent quantum master equation
Get PDFWe put forth a new class of quantum master equations that correctly reproduce
the asymptotic state of an open quantum system beyond the infinitesimally weak
system-bath coupling limit. Our method is based on incorporating the knowledge
of the reduced steady state into its dynamics. The correction not only steers
the reduced system towards a correct steady state but also improves the
accuracy of the dynamics, thereby refining the archetypal Born-Markov
weak-coupling second-order master equations. In case of equilibrium, since a
closed form for the steady state exists in terms of a mean force Gibbs state,
we utilize this form to correct the Redfield quantum master equation. Using an
exactly solvable harmonic oscillator system we benchmark our approach with the
exact solution showing that our method also helps correcting the long-standing
issue of positivity violation, albeit without complete positivity. Our method
of a canonically consistent quantum master equation, opens a new perspective in
the theory of open quantum systems leading to a reduced density matrix accurate
beyond the commonly used Redfield and Lindblad equations, while retaining the
same conceptual and numerical complexity
Stochastic thermodynamics of inertial-like Stuart-Landau dimer
No full text© 2021 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische GesellschaftStuart-Landau limit-cycle oscillators are a paradigm in the study of coherent and incoherent limit cycles. In this work, we generalize the standard Stuart-Landau dimer model to include effects due to an inertia-like term and noise and study its dynamics and stochastic thermodynamics. In the absence of noise (zero-temperature limit), the dynamics show the emergence of a new bistable phase where coherent and incoherent limit cycles coexist. At finite temperatures, we develop a stochastic thermodynamic framework based on the dynamics of a charged particle in a magnetic field to identify physically meaningful heat and work. The stochastic system no longer exhibits the bistable phase but the thermodynamic observables, such as work, exhibit bistability in the temporally metastable regime. We demonstrate that the inertial-like Stuart-Landau dimer operates like a machine, reliably outputting the most work when the oscillators coherently synchronize and unreliable with minimum work output when the oscillators are incoherent. Overall, our results show the importance of coherent synchronization within the working substance in the operation of a thermal machine.11Nsciescopu
Edge mode bifurcations of two-dimensional topological lasers
No full text© 2020 Optical Society of America. Topological lasers are of growing interest as a way to achieve disorder-robust single-mode lasing using arrays of coupled resonators. We study lasing in a two-dimensional coupled resonator lattice exhibiting transitions between trivial and topological phases, which allows us to systematically characterize the lasing modes throughout a topological phase. We show that, unlike conventional topological robustness that requires a sufficiently large bulk band gap, bifurcations in topological edge mode lasing can occur even when the band gap is maximized.We show that linear mode bifurcations from single-mode to multi-mode lasing can occur deep within the topological phase, sensitive to both the pump shape and lattice geometry. We suggest ways to suppress these bifurcations and preserve single-edge mode lasing11sci
Quantum measurements of sums
Get PDF© 2020 American Physical Society. A method is proposed that allows one to infer the sum of the values of an observable taken during contacts with a pointer state. Hereby, the state of the pointer is updated while contacted with the system and remains unchanged between contacts while the system evolves in time. After a prescribed number of such contacts, the position of the pointer is determined by means of a projective measurement. The outcome is specified in terms of a probability distribution function for unitary and Markovian dissipative dynamics and compared with the results of the same number of generalized Gaussian measurements of the considered observable. As a particular example, a qubit is considered with an observable contacting to the pointer that does not commute with the system Hamiltonian11Nsciescopu
Magnetic field induced symmetry breaking in nonequilibrium quantum networks
Get PDFThis research was supported by the Institute for Basic Science in Korea (IBS-R024-Y2), DM acknowledges the Spanish Ministry and the Agencia Espanola de Investigacion (AEI) for financial support under grant FIS2017-84256-P (FEDER funds), and JC acknowledges support from NSF Grant 1800301 and 1836913.We study the effect of an applied magnetic field on the nonequilibrium transport properties of a
general cubic quantum network described by a tight-binding Hamiltonian with specially designed
couplings to the leads that preserve open-system symmetries. We demonstrate that the symmetry
of open systems can be manipulated by the direction of the magnetic field. Starting with all the
symmetries preserved in absence of a field, the anisotropic and isotropic fields systematically break
the symmetries, influencing all nonequilibrium properties. For simple cubic systems, we are able
to identify the steady states that comprise of pure states, bath-dependent states (nonequilibrium
steady states), and also nonphysical states. As an application, we show numerically for large cubic
networks that the symmetry breaking can control nonequilibrium currents and that different
environmental interactions can lead to novel features which can be engineered in artificial
super-lattices and cold atoms.Institute for Basic Science in Korea
IBS-R024-Y2Spanish Government
FIS2017-84256-PAgencia Espanola de Investigacion (AEI)
FIS2017-84256-PNational Science Foundation (NSF)
1800301
183691
Quantifying Information Extraction using Generalized Quantum Measurements
Get PDFObservational entropy is interpreted as the uncertainty an observer making
measurements associates with a system. So far, properties that make such an
interpretation possible rely on the assumption of ideal projective
measurements. We show that the same properties hold even when considering
generalized measurements. Thus, the interpretation still holds: Observational
entropy is a well-defined quantifier determining how influential a given series
of measurements is in information extraction. This generalized framework allows
for the study of the performance of indirect measurement schemes, which are
those using a probe. Using this framework, we first analyze the limitations of
a finite-dimensional probe. Then we study several scenarios of the von Neumann
measurement scheme, in which the probe is a classical particle characterized by
its position. Finally, we discuss observational entropy as a tool for quantum
state inference. Further developed, this framework could find applications in
quantum information processing. For example, it could help in determining the
best read-out procedures from quantum memories and to provide adaptive
measurement strategies alternative to quantum state tomography.Comment: 19+10 pages, 6 figures. v3: name change, changed template to Quantum
journal template, and other minor modifications. v4: significantly improved
presentation and organization, appendix added. v5: changed to PRA styl
Quantum transient heat transport in the hyperparametric oscillator
No full text© 2021 American Physical Society.We explore nonequilibrium quantum heat transport in nonlinear bosonic systems in the presence of a non-Kerr-type interaction governed by hyperparametric oscillation due to two-photon hopping between the two cavities. We estimate the thermodynamic response analytically by constructing the su(2) algebra of the nonlinear Hamiltonian and predict that the system exhibits a negative excitation mode. Consequently, this specific form of interaction enables the cooling of the system by inducing a ground-state transition when the number of particles increases, even though the interaction strength is small. We demonstrate a transition of the heat current numerically in the presence of symmetric coupling between the system and the bath and show long relaxation times in the cooling phase. We compare with the Kerr-type Bose-Hubbard form of interaction induced via cross-phase modulation, which does not exhibit any such transition. We further compute the nonequilibrium heat current in the presence of two baths at different temperatures and observe that the cooling effect for the non-Kerr-type interaction persists. Our findings may help in the manipulation of quantum states using the system's interactions to induce cooling.11Nsciescopu
Degenerated Liouvillians and steady-state reduced density matrices EMBARGO HASTA 07/07/2022
No full textJ.T. acknowledges support by the Institute for Basic Science in Republic of Korea (No. IBS-R024-Y2). D.M. acknowledges the Spanish Ministry and the Agencia Espanola de Investigacion (AEI) for financial support under Grant No. FIS2017-84256-P (FEDER funds). We would like to thank Sai Vinjanampathy for discussions and constructive comments on our manuscript.
DocumentSymmetries in an open quantum system lead to degenerated Liouvillians that physically imply the existence of multiple steady states. In
such cases, obtaining the initial condition independent steady states is highly nontrivial since any linear combination of the true asymptotic
states, which may not necessarily be a density matrix, is also a valid asymptote for the Liouvillian. Thus, in this work, we consider different
approaches to obtain the true steady states of a degenerated Liouvillian. In the ideal scenario, when the open system symmetry operators
are known, we show how these can be used to obtain the invariant subspaces of the Liouvillian and hence the steady states. We then discuss
two other approaches that do not require any knowledge of the symmetry operators. These could be powerful numerical tools to deal with
quantum many-body complex open systems. The first approach that is based on Gram–Schmidt orthonormalization of density matrices
allows us to obtain all the steady states, whereas the second one based on large deviations allows us to obtain the non-degenerated maximum
and minimum current carrying states. We discuss the symmetry-decomposition and the orthonormalization methods with the help of an
open para-benzene ring and examine interesting scenarios such as the dynamical restoration of Hamiltonian symmetries in the long-time
limit and apply the method to study the eigenspacing statistics of the nonequilibrium steady state.Institute for Basic Science in Republic of Korea
IBS-R024-Y2Spanish GovernmentAgencia Española de Investigacion (AEI)
FIS2017-84256-
Temperature-Induced Catch-Slip to Slip Bond Transit in Plasmodium falciparum-Infected Erythrocytes
No full text© 2019 Biophysical SocietyPlasmodium falciparum malaria-infected red blood cells (IRBCs), or erythrocytes, avoid splenic clearance by adhering to host endothelium. Upregulation of endothelial receptors intercellular adhesion molecule-1 (ICAM-1) and cluster of differentiation 36 (CD36) are associated with severe disease pathology. Most in vitro studies of IRBCs interacting with these molecules were conducted at room temperature. However, as IRBCs are exposed to temperature variations between 37°C (body temperature) and 41°C (febrile temperature) in the host, it is important to understand IRBC-receptor interactions at these physiologically relevant temperatures. Here, we probe IRBC interactions against ICAM-1 and CD36 at 37 and 41°C. Single bond force-clamp spectroscopy is used to determine the bond dissociation rates and hence, unravel the nature of the IRBC-receptor interaction. The association rates are also extracted from a multiple bond flow assay using a cellular stochastic model. Surprisingly, IRBC-ICAM-1 bond transits from a catch-slip bond at 37°C toward a slip bond at 41°C. Moreover, binding affinities of both IRBC-ICAM-1 and IRBC-CD36 decrease as the temperature rises from 37 to 41°C. This study highlights the significance of examining receptor-ligand interactions at physiologically relevant temperatures and reveals biophysical insight into the temperature dependence of P. falciparum malaria cytoadherent bond
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