arXiv subjects

C. A. Mikolas

Publications and source records attributed to C. A. Mikolas.

6 recordsLinked to original sources

arXiv2026

High-frequency nonlinear conductivity of a Wigner crystal

Electrons trapped above the surface of superfluid helium are a disorder-free platform for investigating the formation and dynamics of low-dimensional Wigner crystals. A characteristic nonlinear transport feature of this electronic solid suspended above the helium surface is the Bragg-Cherenkov effect, in which the mobility of the smoothly moving crystal is limited by the coherent emission of helium surface waves (ripplons). The effect has been understood in the conventional Cherenkov setting in which the crystal moves at a constant speed. Here we report on transport measurements of electrons on helium confined in a microchannel geometry to investigate the non-equilibrium response of the Wigner solid when it is subjected to a high-frequency driving field. Surprisingly, the experiments reveal a strongly nonlinear transport response of the confined Wigner solid at frequencies nearly an order of magnitude larger than the ripplon frequencies contributing to the conventional Bragg-Cherenkov effect. We relate this observation to the coupling of the Wigner solid to ripplons with higher-order Bragg vectors, which gives rise to a dynamical friction that provides a mechanism for the observed high-frequency pinning.

cond-mat.mes-hall↗

arXiv2025

Plasmon Mode Engineering with Electrons on Helium

An ensemble of electrons trapped above superfluid helium offers a paradigm system for investigating and controlling collective charge dynamics in low-dimensional electronic matter. Of particular interest is the ability to spatially control and engineer surface plasmons for integration with hybrid quantum systems and circuit quantum electrodynamic device architectures. Here we present experiments using an electron-on-helium microchannel device that hosts microwave-frequency plasmons, generated via local microwave excitation in an electrostatically defined central channel. By precisely varying the electron density, we demonstrate tunability of plasmon mode frequencies over several GHz. Additionally, we find that the power dependence of these modes can be used to investigate both homogeneous and inhomogeneous sources of spectral broadening. These results demonstrate the versatility of electrons on helium for probing collective excitations in low-dimensional Coulomb liquids and solids, and demonstrate a path for integrating engineered plasmons in electrons on helium with hybrid circuit quantum electrodynamic systems.

cond-mat.mes-hall↗

arXiv2024

Free-space coupling and characterization of transverse bulk phonon modes in lithium niobate in a quantum acoustic device

Transverse bulk phonons in a multimode integrated quantum acoustic device are excited and characterized via their free-space coupling to a three-dimensional (3D) microwave cavity. These bulk acoustic modes are defined by the geometry of the Y-cut lithium niobate substrate in which they reside and couple to the cavity electric field via a large dipole antenna, with an interaction strength on the order of the cavity line-width. Using finite element modeling (FEM) we determine that the bulk phonons excited by the cavity field have a transverse polarization with a shear velocity matching previously reported values. We demonstrate how the coupling between these transverse acoustic modes and the electric field of the 3D cavity depends on the relative orientation of the device dipole, with a coupling persisting to room temperature. Our study demonstrates the versatility of 3D microwave cavities for mediating contact-less coupling to quantum, and classical, piezoacoustic devices.

quant-ph↗

arXiv2023

Phononic bath engineering of a superconducting qubit

Phonons, the ubiquitous quanta of vibrational energy, play a vital role in the performance of quantum technologies. Conversely, unintended coupling to phonons degrades qubit performance and can lead to correlated errors in superconducting qubit systems. Regardless of whether phonons play an enabling or deleterious role, they do not typically admit control over their spectral properties, nor the possibility of engineering their dissipation to be used as a resource. Here we show that coupling a superconducting qubit to a bath of piezoelectric surface acoustic wave phonons enables a novel platform for investigating open quantum systems. By shaping the loss spectrum of the qubit via the bath of lossy surface phonons, we demonstrate preparation and dynamical stabilization of superposition states through the combined effects of drive and dissipation. These experiments highlight the versatility of engineered phononic dissipation and advance the understanding of mechanical losses in superconducting qubit systems.

quant-ph↗

arXiv2023

Quantum acoustic Fano interference of surface phonons

Quantum acoustic systems, which integrate surface or bulk phonons with superconducting qubits, offer a unique opportunity to investigate phononic $interference$ and $scattering$ processes in the quantum regime. In particular the interaction between a superconducting qubit and a phononic oscillator allows the qubit to sense the oscillator's excitation spectrum and underlying interference effects. Here we present measurements revealing Fano interference of a resonantly trapped piezoelectric surface acoustic wave (SAW) mode with a broad continuum of surface phonons in a system consisting of a SAW resonator coupled to a superconducting qubit. The experiments highlight the existence of additional weakly coupled mechanical modes and their influence on the qubit-phonon interaction and underscore the importance of phononic interference in quantum acoustic architectures that have been proposed for quantum information processing applications.

quant-ph↗

arXiv2022

Helium surface fluctuations investigated with superconducting coplanar waveguide resonator

Recent experiments on the coupling of the in-plane motional state of electrons floating on the surface of liquid helium to a microwave resonator have revealed the importance of helium surface fluctuations to the coherence of this motion. Here we investigate these surface fluctuations by studying the resonance properties of a superconducting coplanar waveguide (CPW) resonator filled with superfluid helium, where a significant fraction of the resonator's electromagnetic mode volume is coupled to the surface dynamics of the liquid. We present preliminary results on real-time CPW resonator frequency shifts driven by helium fluctuations, which are quantified via their power spectral density and compared with measurements using a commercial accelerometer. We find that a considerable contribution to the CPW resonator noise originates from the mechanical vibrations of the helium surface generated by the pulse tube (PT) cryocooler on the cryostat on which the experiments were performed.

quant-ph↗