149 pubs · 1,708 cites · h-index 19
We present an approach to compute time-optimal control of a quantum system which combines quantum brachistochrone and Lax pair techniques and enables efficient investigation of large-scale quantum systems. We illustrate our method by finding the quantum speed limit for a single-particle excitation in a nearest-neighbor-coupled qubit lattice with switchable couplings and fixed sum of their squares. We obtain the solution for a finite system with up to 10 000 qubits and for the effectively infinite lattice closed into ring. As another application of our method, we derive the quantum speed limit for a lattice with time-independent couplings.
Recently, it was predicted that nonreciprocal magneto-electric effect in antiferromagnetic multilayered metamaterials occurs in two distinct versions. One is the conventional axion response, while another one is dual axion response captured by electrodynamics with magnetic charge. Here we investigate a model condensed matter system of spins coupled through antiferromagnetic exchange interaction and derive its effective electromagnetic properties. We predict that this system gives rise to the emergent dual axion field, support our conclusion by numerical simulations and put forward candidate materials.
Demonstration of photonic topological insulators improves directionality of far-field emission, suggesting enhanced control over emitted electromagnetic waves.
Certain topological systems with time-varying Hamiltonian enable quantized and disorder-robust transport of excitations. Here, we introduce the modification of the celebrated Thouless pump when the on-site energies remain fixed, while the nearest and next-nearest-neighbor couplings vary in time. We demonstrate quantized transport of excitations and propose an experimental implementation using an array of evanescently coupled optical waveguides.
Model shows how long-range interactions affect topological phases, suggesting new control methods.
Analytical model reveals increased magnetoelectric polarizability in Tellegen meta-atoms, suggesting advanced optical applications.
Proposed haloscope detects dark matter axions with improved sensitivity, suggesting breakthroughs in dark matter research.
The electromagnetic response of isotropic chiral matter, as described by Carroll–Field–Jackiw electrodynamics, arises in distinct physical contexts ranging from condensed matter systems to Lorentz-violating extensions of high-energy physics. Here, we derive exact expressions for the circularly polarized electromagnetic fields that contribute independently to Cherenkov radiation in isotropic chiral matter. Each spectral energy distribution is gauge-invariant and positive, yielding radiation that emerges at a characteristic angle, akin to the standard case. Furthermore, we identify specific frequency ranges that permit zero, one, or two Cherenkov cones for a given setup. Remarkably, one sector of the model allows for the existence of threshold-free Cherenkov radiation arising from slowly-moving charges.
Effective axion fields emerge in condensed matter and photonic systems with broken parity and time-reversal symmetries resulting in nonreciprocal optical phenomena. Here, we predict a distinct type of electromagnetic response which has the same symmetry properties as an axion one, manifests itself only at the boundaries of the material and features the same coupling to incident plane waves. However, the response to the external sources introduced inside is profoundly different, allowing one to distinguish the predicted dual axion field experimentally. We prove that the behavior of such materials is captured by electrodynamics with magnetic charge, put forward a specific metamaterial realizing this physics and suggest possible experiments to observe it. We anticipate that this response is general and occurs in a variety of photonic and condensed matter structures. Effective axion fields emerge in a variety of condensed matter and photonic structures. Here, the authors predict a distinct dual axion response arising in metamaterials and, potentially, some condensed matter systems and captured by electrodynamics with magnetic charge.
Recent technological advances have allowed the fabrication of large arrays of coupled qubits, serving as prototypes for quantum processors. However, the optimal control of such systems remains notoriously challenging, limiting the potential of large-scale quantum systems. Here, we investigate a model problem of quantum state transfer in a large nearest-neighbor-coupled qubit array. We derive an optimal control strategy that simultaneously achieves maximal fidelity and minimal transfer time, reaching the quantum speed limit in a lattice with time-varying couplings.
Spatial structuring of materials at subwavelength scales underlies the concept of metamaterials possessing exotic properties beyond those of the constituent media. Temporal modulation of material parameters enables further functionalities. Here, we show that high-frequency oscillations of spatially uniform magnetization generate an effective dynamic axion field embedding the amplitude and phase of magnetization oscillations. This allows one to map ultrafast magnetization dynamics using a probe signal with much lower frequency.
We consider a medium exhibiting nonreciprocal magneto-electric effect known as Tellegen response captured by the equations of axion electrodynamics. Here, we investigate the implications of the complex-valued Tellegen response, discuss the conditions for its emergence and possible material realizations outlining a route to its experimental identification from the Stokes parameters of the reflected light.
The Tellegen response is a special type of nonreciprocal magnetoelectric coupling which has long remained elusive in photonics and is extremely weak in condensed matter. It is widely accepted that the Tellegen coefficient is restricted by χ²<εμ, where ε and μ are the permittivity and permeability of the material. Here, we demonstrate that this restriction is lifted in the medium with several close resonances, which provides a theoretical foundation for a giant Tellegen response and enhanced nonreciprocal phenomena.
Evanescently coupled waveguide arrays provide a tabletop platform to realize a variety of Hamiltonians, where physical waveguides correspond to the individual sites of a tight-binding lattice. Nontrivial spatial structure of the waveguide modes enriches this picture and uncovers further possibilities. Here, we demonstrate that the effective coupling between p -like modes of adjacent photonic waveguides changes its sign depending on their relative orientation vanishing for proper alignment at a so-called invisibility angle . Using femtosecond laser-written waveguides, we demonstrate this experimentally for p -mode dimers and graphene-like photonic lattices exhibiting quasi-flat bands at this angle. We observe diffraction-free propagation of corner and bulk states, providing robust experimental evidence of a two-dimensional Aharonov–Bohm-like caging in an optically switchable system.
The quantum brachistochrone method has recently emerged as a technique that allows one to implement the desired unitary evolution operator in a physical system within a minimal time. Here, we apply this approach to the problem of time-optimal quantum state transfer in an array of three qubits with time-varying nearest-neighbor couplings and analytically derive the fastest protocol.
We consider a multilayered metamaterial composed of anisotropic layers with in-plane anisotropy axes periodically rotated with respect to each other. Due to the breaking of inversion symmetry, the structure develops an effective chirality. We derive the effective chirality tensor of the metamaterial describing both normal and oblique incidence scenarios. We also identify the arrangement of the layers maximizing chiral response for the fixed lattice period, wavelength, and anisotropy of the layers.
Nonlinear effects and non-Hermitian phenomena unveil additional intricate facets in topological matter physics. They can naturally intertwine to enable advanced functionalities in topolectrical circuits and photonic structures. Here, we illustrate the subtle interplay between nonlinearity and non-Hermiticity by examining the characteristics of small wave perturbations on the background of the self-induced topological edge state in the nonlinear Su–Schrieffer–Heeger model. We demonstrate that their underlying physics is captured by the non-Hermitian effective Hamiltonian, which features nonreciprocal coupling terms and entails unconventional time-dependent field localization.
Effective axion fields in condensed matter and photonics are manifested as P- and T-odd contributions to the electromagnetic response. Here, we show that the phenomena previously attributed to the effective axion fields have two distinct physical origins. One of them corresponds to the standard axion electrodynamics, while another provides its dual-symmetric version having the same symmetry and featuring similar but distinguishable optical properties. We present an example system described by the dual-symmetric modification of axion electrodynamics, derive the key predictions and pinpoint experimentally observable distinctions between the two versions of axion-type response.
Non-linear effects and non-Hermitian phenomena unveil additional intricate facets in topological matter physics. They can naturally intertwine to enable advanced functionalities in topoelectrical circuits and photonic structures. Here, we illustrate the subtle interplay between nonlinearity and non-Hermiticity by examining the characteristics of small wave perturbations on the background of the self-induced topological edge state in the nonlinear Su-Schrieffer-Heeger model. We demonstrate that their underlying physics is captured by the non-Hermitian effective Hamiltonian, which features nonreciprocal coupling terms and entails unconventional time-dependent field localization.
Spatial structuring of materials at subwavelength scales underlies the concept of metamaterials possessing exotic properties beyond those of the constituent media. Temporal modulation of material parameters enables further functionalities. Here, we show that high-frequency oscillations of spatially uniform magnetization generate an effective dynamic axion field embedding the amplitude and phase of magnetization oscillations. This allows one to map ultrafast magnetization dynamics using a probe signal with much lower frequency.