Design and Optimization of Spin Dynamics in Ge Quantum Dots: g-Factor Modulation, Dephasing Sweet Spots, and Phonon-Induced Relaxation

• URL: http://arxiv.org/abs/2509.10731v2
• Date: Tue, 16 Sep 2025 13:32:43 GMT
• Title: Design and Optimization of Spin Dynamics in Ge Quantum Dots: g-Factor Modulation, Dephasing Sweet Spots, and Phonon-Induced Relaxation
• Authors: Ngoc Duong, Daryoosh Vashaee,
• Abstract summary: We present a three-dimensional study of gate-defined quantum dot hole spin qubits in strained Si$_0.2$Ge$_0.8$/Ge heterostructures.<n>We quantify the impact of device size and gate bias on wavefunction localization, electric-field-induced g-factor modulation, and identify "sweet spots" in vertical electric field where g-factor sensitivity to charge noise is minimized.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Accurate modeling of spin dynamics in hole-based quantum dot qubits demands high-fidelity simulations that capture realistic device geometries, material interfaces, and self-consistent electrostatics. Here, we present a comprehensive three-dimensional study of gate-defined quantum dot hole spin qubits in strained Si$_{0.2}$Ge$_{0.8}$/Ge heterostructures. In contrast to prior work relying on idealized confinement or decoupled Poisson-Schr\"odinger treatments, our approach combines self-consistent electrostatics with a four-band Luttinger-Kohn Hamiltonian to resolve spin-orbit interactions, wavefunction asymmetries, and g-tensor anisotropies in realistic device structures. We quantify the impact of device size and gate bias on wavefunction localization, electric-field-induced g-factor modulation, and identify "sweet spots" in vertical electric field where g-factor sensitivity to charge noise is minimized, enhancing spin dephasing times. Spin relaxation due to phonon coupling is also modeled, revealing size-dependent T1 behavior consistent with strong Rashba-type spin-orbit coupling and a magnetic-field scaling near $B^{-8}$. This work establishes a predictive modeling framework for optimizing spin coherence in planar Ge quantum dots and provides quantitative design guidance for scalable, electrically controlled hole spin qubits in group-IV semiconductors.

Related papers

• Exploring the mechanisms of transverse relaxation of copper(II)-phthalocyanine spin qubits [9.695800379962364]
  Molecular spin qubits are promising candidates for quantum technologies, but their performance is limited by decoherence arising from diverse mechanisms.<n>Here we present a systematic experimental and theoretical framework for analyzing the mechanisms of transverse relaxation in copper(II) phthalocyanine (CuPc) diluted into diamagnetic phthalocyanine hosts.<n>Our work identifies favorable values of the electron spin density for quantum applications, and provides a transferable methodology for predicting ensemble coherence times.
  arXiv  Detail & Related papers  (2025-11-05T05:32:56Z)
• Phonon-Coupled Hole-Spin Qubits in High-Purity Germanium: Design and Modeling of a Scalable Architecture [0.0]
  We present a design and modeling of a scalable quantum processor architecture utilizing hole-spin qubits defined in gate-controlled germanium (Ge) quantum dots.<n>The architecture exploits the strong, electrically tunable spin-orbit interactions intrinsic to hole states in Ge, integrated with high-quality phononic crystal cavities (PnCCs) to enable fully electrical qubit control and phonon-mediated coupling.
  arXiv  Detail & Related papers  (2025-04-16T16:14:30Z)
• Effect of disorder and strain on the operation of planar Ge hole spin qubits [0.34630926944621643]
  Germanium quantum dots in strained $textGe/textSi_1-xtextGe_x$ heterostructures exhibit fast and coherent hole qubit control in experiments.<n>We numerically address the effects of random alloy disorder and gate-induced strain on the operation of planar Ge hole spin qubits.
  arXiv  Detail & Related papers  (2025-02-10T19:00:03Z)
• Electron-Electron Interactions in Device Simulation via Non-equilibrium Green's Functions and the GW Approximation [71.63026504030766]
  electron-electron (e-e) interactions must be explicitly incorporated in quantum transport simulation.<n>This study is the first one reporting large-scale atomistic quantum transport simulations of nano-devices under non-equilibrium conditions.
  arXiv  Detail & Related papers  (2024-12-17T15:05:33Z)
• Slow semiclassical dynamics of a two-dimensional Hubbard model in disorder-free potentials [77.34726150561087]
  We show that introduction of harmonic and spin-dependent linear potentials sufficiently validates fTWA for longer times. In particular, we focus on a finite two-dimensional system and show that at intermediate linear potential strength, the addition of a harmonic potential and spin dependence of the tilt, results in subdiffusive dynamics.
  arXiv  Detail & Related papers  (2022-10-03T16:51:25Z)
• Spin Current Density Functional Theory of the Quantum Spin-Hall Phase [59.50307752165016]
  We apply the spin current density functional theory to the quantum spin-Hall phase. We show that the explicit account of spin currents in the electron-electron potential of the SCDFT is key to the appearance of a Dirac cone.
  arXiv  Detail & Related papers  (2022-08-29T20:46:26Z)
• Probing dynamics of a two-dimensional dipolar spin ensemble using single qubit sensor [62.997667081978825]
  We experimentally investigate individual spin dynamics in a two-dimensional ensemble of electron spins on the surface of a diamond crystal. We show that this anomalously slow relaxation rate is due to the presence of strong dynamical disorder. Our work paves the way towards microscopic study and control of quantum thermalization in strongly interacting disordered spin ensembles.
  arXiv  Detail & Related papers  (2022-07-21T18:00:17Z)
• Gate-based spin readout of hole quantum dots with site-dependent $g-$factors [101.23523361398418]
  We experimentally investigate a hole double quantum dot in silicon by carrying out spin readout with gate-based reflectometry. We show that characteristic features in the reflected phase signal arising from magneto-spectroscopy convey information on site-dependent $g-$factors in the two dots.
  arXiv  Detail & Related papers  (2022-06-27T09:07:20Z)
• Ab initio Ultrafast Spin Dynamics in Solids [0.7874708385247353]
  We present a first-principles real-time density-matrix approach based on Lindblad dynamics to simulate ultrafast spin dynamics for general solid-state systems. We find that the electron-electron scattering is negligible at room temperature but becomes dominant at low temperatures for spin relaxation in n-type GaAs.
  arXiv  Detail & Related papers  (2020-12-16T02:49:47Z)
• Simulated coherent electron shuttling in silicon quantum dots [0.0]
  Gate-defined silicon quantum dots are numerically simulated. Coherent spin transport is simulated by including spin-orbit and valley terms in an effective Hamiltonian. Results pertain to proposals for large-scale spin qubit processors in isotopically purified silicon.
  arXiv  Detail & Related papers  (2020-03-18T02:36:40Z)
• Entanglement generation via power-of-SWAP operations between dynamic electron-spin qubits [62.997667081978825]
  Surface acoustic waves (SAWs) can create moving quantum dots in piezoelectric materials. We show how electron-spin qubits located on dynamic quantum dots can be entangled.
  arXiv  Detail & Related papers  (2020-01-15T19:00:01Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.