Molecular van der Waals Fluids in Cavity Quantum Electrodynamics
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Transition from Lorentz to Fano Spectral Line Shapes in Nonrelativistic Quantum Electrodynamics
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Materials Science↗
Random access quantum information processors using multimode circuit quantum electrodynamics
Qubit connectivity is an important property of a quantum processor, with an ideal processor having random access—the ability of arbitrary qubit pairs to interact directly. This a challenge with superconducting circuits, as state-of-the-art architectures rely on only nearest-neighbor coupling. Here, we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-qubit memory, with a Josephson junction transmon circuit serving as the central processor. The quantum memory uses the eigenmodes of a linear array of coupled superconducting resonators. We selectively stimulate vacuum Rabi oscillations between the transmon and individual eigenmodes through parametric flux modulation of the transmon frequency. Utilizing these oscillations, we perform a universal set of quantum gates on 38 arbitrary pairs of modes and prepare multimode entangled states, all using only two control lines. We thus achieve hardware-efficient random access multi-qubit control in an architecture compatible with long-lived microwave cavity-based quantum memories.
97 MATHEMATICS AND COMPUTING↗
Engineering anisotropic electrodynamics at the graphene/CrSBr interface
Abstract Graphene is a privileged 2D platform for hosting confined light-matter excitations known as surface plasmon polaritons (SPPs), as it possesses low intrinsic losses and a high degree of optical confinement. However, the isotropic nature of graphene limits its ability to guide and focus SPPs, making it less suitable than anisotropic elliptical and hyperbolic materials for polaritonic lensing and canalization. Here, we present graphene/CrSBr as an engineered 2D interface that hosts highly anisotropic SPP propagation across mid-infrared and terahertz energies. Using scanning tunneling microscopy, scattering-type scanning near-field optical microscopy, and first-principles calculations, we demonstrate mutual doping in excess of 10 13 cm –2 holes/electrons between the interfacial layers of graphene/CrSBr. SPPs in graphene activated by charge transfer interact with charge-induced electronic anisotropy in the interfacial doped CrSBr, leading to preferential SPP propagation along the quasi-1D chains that compose each CrSBr layer. This multifaceted proximity effect both creates SPPs and endows them with anisotropic propagation lengths that differ by an order-of-magnitude between the in-plane crystallographic axes of CrSBr.
Science & Technology - Other Topics↗
Current-driven nonequilibrium electrodynamics in graphene revealed by nano-infrared imaging
Not Available
Dong, Y. (ORCID:000000025996642X)↗
On-demand directional microwave photon emission using waveguide quantum electrodynamics
Routing quantum information between non-local computational nodes is a foundation for extensible networks of quantum processors. Quantum information transfer between arbitrary nodes is generally mediated either by photons that propagate between them or by resonantly coupling nearby nodes. The utility is determined by the type of emitter, propagation channel and receiver. Conventional approaches involving propagating microwave photons have limited fidelity due to photon loss and are often unidirectional, whereas architectures that use direct resonant coupling are bidirectional in principle but can generally accommodate only a few local nodes. Here we demonstrate high-fidelity, on-demand, directional, microwave photon emission. We do this using an artificial molecule comprising two superconducting qubits strongly coupled to a bidirectional waveguide, effectively creating a chiral microwave waveguide. Quantum interference between the photon emission pathways from the molecule generates single photons that selectively propagate in a chosen direction. This circuit will also be capable of photon absorption, making it suitable for building interconnects within extensible quantum networks.
42 ENGINEERING↗
Low energy electrodynamics of CrI 3 layered ferromagnet
We report on the optical properties from terahertz (THz) to Near-Infrared (NIR) of the layered magnetic compound CrI 3 at various temperatures, both in the paramagnetic and ferromagnetic phase. In the NIR spectral range, we observe an insulating electronic gap around 1.1 eV which strongly hardens with decreasing temperature. The blue shift observed represents a record in insulating materials and it is a fingerprint of a strong electron-phonon interaction. Moreover, a further gap hardening is observed below the Curie temperature, indicating the establishment of an effective interaction between electrons and magnetic degrees of freedom in the ferromagnetic phase. Similar interactions are confirmed by the disappearance of some phonon modes in the same phase, as expected from a spin-lattice interaction theory. Therefore, the optical properties of CrI 3 reveal a complex interaction among electronic, phononic and magnetic degrees of freedom, opening many possibilities for its use in 2-Dimensional heterostructures.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Non-linear non-local molecular electrodynamics with nano-optical fields
The interaction of optical fields sculpted on the nano-scale with matter may not be described by the dipole approximation since the fields may vary appreciably across the molecular length scale. Rather than incrementally adding higher multipoles, it is advantageous and more physically transparent to describe the optical process using non-local response functions that intrinsically include all multi-poles. In this work, we present a semi-classical approach for calculating non-local response functions based on the minimal coupling Hamiltonian. The first, second, and third order response functions are expressed in terms of correlation functions of the charge and the current densities. Finally, this approach is based on the gauge invariant current rather than the polarization, and on the vector potential rather than the electric and magnetic fields.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Physics-constrained 3D convolutional neural networks for electrodynamics
We present a physics-constrained neural network (PCNN) approach to solving Maxwell’s equations for the electromagnetic fields of intense relativistic charged particle beams. We create a 3D convolutional PCNN to map time-varying current and charge densities J(r, t) and ρ(r, t) to vector and scalar potentials A(r, t) and φ(r, t) from which we generate electromagnetic fields according to Maxwell’s equations: B = ∇ × A and E = −∇φ − ∂A/∂t. Our PCNNs satisfy hard constraints, such as ∇ · B = 0, by construction. Soft constraints push A and φ toward satisfying the Lorenz gauge.
97 MATHEMATICS AND COMPUTING↗
Universal linear and nonlinear electrodynamics of a Dirac fluid
Significance Electrons in pristine solids behave as a hydrodynamic fluid in a certain range of temperatures and frequencies. We show that the response of such a fluid to an electromagnetic field is different from what is predicted by the usual kinetic theory. Certain aspects of this response are universal, for example, a direct relation between the linear and second-order nonlinear optical conductivities. Discovery of this relation enriches our understanding of the light–matter interaction in diverse electron systems and new materials such as graphene.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
On the propagation of electrodynamic waves along a wire by A. Sommerfeld
This is a translation of a classic paper of Arnold Sommerfeld published in 1899. It reflected the first rigorous theory of waves traveling on a resistive wire of finite radius. General solutions inside and outside the wire are written in terms of Bessel functions, and the boundary condition at the surface is well approximated by a transcendental equation. A detailed analysis of the equation demonstrates that surface waves are supported, which decay exponentially with the radial distance from the wire. The propagation velocity, less than c, and the longitudinal damping rate are related to the material properties of the wire. An historical overview of related work, on surface waves and open waveguides, is given by the translator.
97 MATHEMATICS AND COMPUTING↗
Electrodynamics of binary neutron star mergers
We consider electromagnetic interaction and precursor emission of merging neutron stars. Orbital motion of the magnetized neutron star may revive pair production within the common magnetosphere years before the merger, igniting pulsar-like magnetospheric dynamics. We identify two basic scenarios: (i) only one star is magnetized (1M-DNS scenario) and (ii) both stars are magnetized (2M-DNS scenario). Inductively created electric fields can have component along the total magnetic field (gaps) and/or the electric field may exceed the value of the local magnetic field. The key to the detection is orbital modulation of the emission. If only one star is magnetized (1M-DNS scenario) the emission is likely to be produced along the direction of the magnetic field at the location of the secondary; then, if the magnetic axis is misaligned with the orbital spin, this direction is modulated on the orbital period. For the 2M-DNS scenario, the structure of the common magnetosphere of the non-rotating neutron stars is complicated, with gaps, but no E > B regions; there is strong orbital variations for the case of misaligned magnetic moments. For the same parameters of neutron stars the 2M-DNS scenario has intrinsically higher potential than the 1M-DNS one. The overall powers are not very high, ≤10 45 erg s -1 ; the best chance to detect electromagnetic precursors to the merging neutron stars is if the interaction of their magnetospheres leads to the production of pulsar-like coherent radio emission modulated at the orbital period, with luminosity of up to ~1 Jankys at the time of the merger.
79 ASTRONOMY AND ASTROPHYSICS↗
Quasiclassical modeling of cavity quantum electrodynamics
Not Available
Li, Tao E. (ORCID:0000000303615687)↗
Mixed quantum-classical electrodynamics: Understanding spontaneous decay and zero-point energy
The dynamics of an electronic two-level system coupled to an electromagnetic field are simulated explicitly for one- and three-dimensional systems through semiclassical propagation of the Maxwell-Liouville equations. Here, we consider three flavors of mixed quantum-classical dynamics: (i) the classical path approximation (CPA), (ii) Ehrenfest dynamics, and (iii) symmetrical quasiclassical (SQC) dynamics. Our findings are as follows: (i) The CPA fails to recover a consistent description of spontaneous emission, (ii) a consistent “spontaneous” emission can be obtained from Ehrenfest dynamics, provided that one starts in an electronic superposition state, and (iii) spontaneous emission is always obtained using SQC dynamics. Using the SQC and Ehrenfest frameworks, we further calculate the dynamics following an incoming pulse, but here we find very different responses: SQC and Ehrenfest dynamics deviate sometimes strongly in the calculated rate of decay of the transient excited state. Nevertheless, our work confirms the earlier observations by Miller [J. Chem. Phys. 69, 2188 (1978)] that Ehrenfest dynamics can effectively describe some aspects of spontaneous emission and highlights interesting possibilities for studying light-matter interactions with semiclassical mechanics.
74 ATOMIC AND MOLECULAR PHYSICS↗
Anomalous electrodynamics and quantum geometry in the Dirac-Harper model for a graphene bilayer
In this work, graphene bilayers with layer antisymmetric strains are studied using the Dirac-Harper model for a pair of single layer Dirac Hamiltonians coupled by a one-dimensional moiré-periodic interlayer tunneling amplitude. This model hosts low energy, nearly dispersionless bands near charge neutrality that support anomalous polarizations of its charge multipole distributions. These are analyzed introducing a generalized Berry curvature that encodes the field-induced dynamics of multipole fields allowed in a chiral medium with time reversal symmetry. The formulation identifies a reciprocity relation between responses to layer-symmetric and layer-antisymmetric in-plane electric fields and reveals momentum-space quantum oscillations produced by a spatial pattern of band inversions on the moiré scale.
36 MATERIALS SCIENCE↗