Spectroscopy and Coherent Control of Two-Level System Defect Ensembles Using a Broadband 3D Waveguide

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Hauptverfasser: Wang, Qianxu, Salcedo-Gallo, Juan S., Bedkihal, Salil, Xia, Tian, Olszewski, Maciej W., Fatemi, Valla, Fitzpatrick, Mattias
Format: Preprint
Veröffentlicht: 2025
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author Wang, Qianxu
Salcedo-Gallo, Juan S.
Bedkihal, Salil
Xia, Tian
Olszewski, Maciej W.
Fatemi, Valla
Fitzpatrick, Mattias
author_facet Wang, Qianxu
Salcedo-Gallo, Juan S.
Bedkihal, Salil
Xia, Tian
Olszewski, Maciej W.
Fatemi, Valla
Fitzpatrick, Mattias
contents Defects in solid-state materials play a central role in determining coherence, stability, and performance in quantum technologies. Although narrowband techniques can probe specific resonances with high precision, a broadband spectroscopic approach captures the full spectrum of defect properties and dynamics. Two-level system (TLS) defects in amorphous dielectrics are a particularly important example because they are major sources of decoherence and energy loss in superconducting quantum devices. However, accessing and characterizing their collective dynamics remains far more challenging than probing individual TLS defects. Building on our previously developed Broadband Cryogenic Transient Dielectric Spectroscopy (BCTDS) technique, we study the coherent control and time-resolved dynamics of TLS defect ensembles over a wide frequency range of 3-5 GHz without requiring full device fabrication, revealing quantum interference effects, memory-dependent dynamics, and dressed-state evolution within the TLS defect bath. The spectral response reveals distinct V-shaped structures corresponding to the bare eigenmode frequencies. Using these features, we extract a TLS defect spectral density of 84 GHz^-1 for a silicon sample, across a 4.1-4.6 GHz span. Furthermore, we systematically investigate amplitude- and phase-controlled interference fringes for multiple temperatures and inter-pulse delays, providing direct evidence of coherent dynamics and control. A driven minimal spin model with dipole-dipole interactions that qualitatively capture the observed behavior is presented. Our results establish BCTDS as a versatile platform for broadband defect spectroscopy, offering new capabilities for diagnosing and mitigating sources of decoherence, engineering many-body dynamics, and exploring non-equilibrium phenomena in disordered quantum systems.
format Preprint
id arxiv_https___arxiv_org_abs_2512_05934
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spectroscopy and Coherent Control of Two-Level System Defect Ensembles Using a Broadband 3D Waveguide
Wang, Qianxu
Salcedo-Gallo, Juan S.
Bedkihal, Salil
Xia, Tian
Olszewski, Maciej W.
Fatemi, Valla
Fitzpatrick, Mattias
Quantum Physics
Defects in solid-state materials play a central role in determining coherence, stability, and performance in quantum technologies. Although narrowband techniques can probe specific resonances with high precision, a broadband spectroscopic approach captures the full spectrum of defect properties and dynamics. Two-level system (TLS) defects in amorphous dielectrics are a particularly important example because they are major sources of decoherence and energy loss in superconducting quantum devices. However, accessing and characterizing their collective dynamics remains far more challenging than probing individual TLS defects. Building on our previously developed Broadband Cryogenic Transient Dielectric Spectroscopy (BCTDS) technique, we study the coherent control and time-resolved dynamics of TLS defect ensembles over a wide frequency range of 3-5 GHz without requiring full device fabrication, revealing quantum interference effects, memory-dependent dynamics, and dressed-state evolution within the TLS defect bath. The spectral response reveals distinct V-shaped structures corresponding to the bare eigenmode frequencies. Using these features, we extract a TLS defect spectral density of 84 GHz^-1 for a silicon sample, across a 4.1-4.6 GHz span. Furthermore, we systematically investigate amplitude- and phase-controlled interference fringes for multiple temperatures and inter-pulse delays, providing direct evidence of coherent dynamics and control. A driven minimal spin model with dipole-dipole interactions that qualitatively capture the observed behavior is presented. Our results establish BCTDS as a versatile platform for broadband defect spectroscopy, offering new capabilities for diagnosing and mitigating sources of decoherence, engineering many-body dynamics, and exploring non-equilibrium phenomena in disordered quantum systems.
title Spectroscopy and Coherent Control of Two-Level System Defect Ensembles Using a Broadband 3D Waveguide
topic Quantum Physics
url https://arxiv.org/abs/2512.05934