Atomistic compositional details and their importance for spin qubits in isotope-purified silicon-germanium quantum wells

• URL: http://arxiv.org/abs/2405.19974v1
• Date: Thu, 30 May 2024 11:57:18 GMT
• Title: Atomistic compositional details and their importance for spin qubits in isotope-purified silicon-germanium quantum wells
• Abstract summary: Isotope composition depth profiles in a SiGe28$Si/SiGe heterostructure are analyzed. Spin-echo dephasing times and valley energy splittings have been observed for single spin qubits in this quantum well (QW) heterostructure.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Understanding crystal characteristics down to the atomistic level increasingly emerges as a crucial insight for creating solid state platforms for qubits with reproducible and homogeneous properties. Here, isotope composition depth profiles in a SiGe/$^{28}$Si/SiGe heterostructure are analyzed with atom probe tomography (APT) and time-of-flight secondary-ion mass spectrometry. Spin-echo dephasing times $T_2^{echo}=128 \mu s$ and valley energy splittings around $200 \mu eV$ have been observed for single spin qubits in this quantum well (QW) heterostructure, pointing towards the suppression of qubit decoherence through hyperfine interaction or via scattering between valley states. The concentration of nuclear spin-carrying $^{29}$Si is 50 ppm in the $^{28}$Si QW. APT allows to uncover that both the top SiGe/$^{28}$Si and the bottom $^{28}$Si/SiGe interfaces of the QW are shaped by epitaxial growth front segregation signatures on a few monolayer scale. A subsequent thermal treatment broadens the top interface by about two monolayers, while the width of the bottom interface remains unchanged. Using a tight-binding model including SiGe alloy disorder, these experimental results suggest that the combination of the slightly thermally broadened top interface and of a minimal Ge concentration of $0.3 \%$ in the QW, resulting from segregation, is instrumental for the observed large valley splitting. Minimal Ge additions $< 1 \%$, which get more likely in thin QWs, will hence support high valley splitting without compromising coherence times. At the same time, taking thermal treatments during device processing as well as the occurrence of crystal growth characteristics into account seems important for the design of reproducible qubit properties.

Related papers

• Strongly anisotropic non-Kramers electron spin as a quantum coherence probe of angular fluctuations [0.0]
  Strongly anisotropic non-Kramers rare-earth ions combine giant longitudinal g-factors with a vanishing transverse component imposed by time-reversal impurities.<n>We show that this sensitivity carries a dual identity: it is simultaneously an overlooked decoherence channel and the basis for a spin-coherence-based angular probe.
  arXiv  Detail & Related papers  (2026-09-03T15:24:36Z)
• Tailoring pure valley-Zeeman spin-orbit coupling in WSe$_2$-encapsulated monolayer graphene [42.39722022913058]
  Engineering proximity effects in twisted van der Waals heterostructures offers a powerful platform for designing electronic properties.<n>We report pure valley-Zeeman spin-orbit coupling in monolayer graphene, achieved by encapsulation between two parallel twisted WSe$$ monolayers.<n>We also demonstrate the ability to completely quench the proximity spin-orbit coupling by tuning the encapsulated geometry.
  arXiv  Detail & Related papers  (2026-06-02T07:43:48Z)
• Co-optimization of spin coherence and valley splitting in Si/SiGe heterostructures [1.1549572298362782]
  We use density functional theory to optimize the valley splitting and spin dephasing time in realistic Si/SiGe heterostructures.<n> sharper Si/SiGe interfaces in general result in larger valley splittings and longer spin dephasing times.
  arXiv  Detail & Related papers  (2026-05-29T14:20:52Z)
• Towards second-long electron spin coherence of a telecom quantum emitter in naturally abundant CeO$_2$ [0.0]
  Erbium doped cerium oxide (CeO$$) is an attractive candidate due to the ultralow concentration of nuclear spins in the host matrix.<n>We show that at dilute doping concentration (of the order of 10 ppb) and sub-Kelvin temperatures, operation near clock transitions enables coherence times to approach the second timescale.
  arXiv  Detail & Related papers  (2026-05-08T06:36:32Z)
• Quantum Hall Effect at 0.002T [46.680073344221626]
  We demonstrate a significant reduction in external inhomogeneity using a double-layer graphene architecture separated by an ultra-thin hexagonal boron nitride layer.<n>Shubnikov de-Haas oscillations emerge at magnetic fields below 1 mT, while integer quantum Hall features are observed at 0.002T.<n>These results demonstrate the platform's suitability for investigating strongly correlated electronic phases in graphene-based heterostructures.
  arXiv  Detail & Related papers  (2026-01-22T14:40:33Z)
• Revisiting the Broken Symmetry Phase of Solid Hydrogen: A Neural Network Variational Monte Carlo Study [42.40832340604796]
  We show that even the broken symmetry phase observed around 130GPa requires revisiting due to its intricate coupling of electronic and nuclear degrees of freedom.<n>Our calculations reveal an unreported ground-state structure candidate for the broken symmetry phase with $Cmcm$ space group symmetry.<n>These results shed new light on the phase diagram of high-pressure hydrogen and call for further experimental verifications.
  arXiv  Detail & Related papers  (2025-12-19T15:36:27Z)
• High temperature superradiant phase transition in novel quantum structures with complex network interface [44.99833362998488]
  We propose a novel quantum material concept, which enables super- and/or ultrastrong interaction of two-level systems with the photonic field in a complex network.<n>We characterize the statistical properties of networks by the first, $langlekrangle$, and second normalized, $zetaequivlanglek2rangle/langlekrangle$, moments for node degree distribution.
  arXiv  Detail & Related papers  (2025-07-22T07:56:45Z)
• Phase Transitions in Open Dicke Model: a degenerate perturbation theory approach [0.0]
  We study the steady-state behavior of the open Dicke model, which describes the collective interaction of $N$ spin-$1/2$ particles with a lossy, quantized cavity mode.<n>While the standard model conserves total spin, Kirton and Keeling citePhysRevLett.118.123602 demonstrated that even infinitesimal homogeneous local dephasing destroys this phase transition.<n>Our results bridge the quantum Rabi model and Dicke physics, elucidate the roles of dephasing and decay in collective quantum effects, and apply broadly to open quantum systems with degenerate steady
  arXiv  Detail & Related papers  (2025-05-19T04:33:30Z)
• Valley Splitting Correlations Across a Silicon Quantum Well [0.0]
  We study valley splitting variations in a 1D quantum dot array manufactured by Intel. Our results develop the mesoscopic understanding of Si/SiGe heterostructures necessary for scalable device design.
  arXiv  Detail & Related papers  (2025-04-16T19:41:11Z)
• (111) Si spin qubits constructed on L point of band structure [0.0]
  Si spin qubits have state-of-the-art miniaturization, integration, and variation-reduction-technologies. New measures are proposed to address issues of relaxation and decoherence time, stabilization of valley-splitting control, and reduction of variation caused by the roughness of the interface. It is hoped that prototype silicon spin qubits constructed on (111) Si crystals will be developed and that the proposed device structure will help implement quantum computers based on Si devices.
  arXiv  Detail & Related papers  (2025-01-23T10:46:35Z)
• Bottom-up Fabrication of 2D Rydberg Exciton Arrays in Cuprous Oxide [34.82692226532414]
  Cuprous oxide ($textCu_2textO$) has emerged as a promising medium for scalable quantum technology. This study demonstrates the bottom-up fabrication of site-selective arrays of $textCu_2textO$ microparticles.
  arXiv  Detail & Related papers  (2024-08-07T16:28:59Z)
• Ancilla quantum measurements on interacting chains: Sensitivity of entanglement dynamics to the type and concentration of detectors [46.76612530830571]
  We consider a quantum many-body lattice system that is coupled to ancillary degrees of freedom (detectors'') We explore the dynamics of density and of entanglement entropy in the chain, for various values of $rho_a$ and $M$.
  arXiv  Detail & Related papers  (2023-11-21T21:41:11Z)
• Microwave-based quantum control and coherence protection of tin-vacancy spin qubits in a strain-tuned diamond membrane heterostructure [54.501132156894435]
  Tin-vacancy center (SnV) in diamond is a promising spin-photon interface with desirable optical and spin properties at 1.7 K. We introduce a new platform that overcomes these challenges - SnV centers in uniformly strained thin diamond membranes. The presence of crystal strain suppresses temperature dependent dephasing processes, leading to a considerable improvement of the coherence time up to 223 $mu$s at 4 K.
  arXiv  Detail & Related papers  (2023-07-21T21:40:21Z)
• Nuclear Spin-Depleted, Isotopically Enriched 70Ge/28Si70Ge Quantum Wells [0.0]
  This work demonstrates the epitaxial growth of $text73$Ge-depleted isotopically enriched $text70$Ge/SiGe quantum wells. The measured average distance between nuclear spins reaches 3-4 nm in $text70$Ge/$text28$Si$text70$Ge, which is an order of magnitude larger than in natural Ge/SiGe heterostructures.
  arXiv  Detail & Related papers  (2023-06-06T22:53:30Z)
• Valleytronic full configuration-interaction approach: An application to the excitation spectra of Si double-dot qubits [0.0]
  We study the influence of strong electron-electron interactions and Wigner-molecule (WM) formation on the spectra of Si qubits. We present results for both the $E_rm ST E_V$ and $E_rm ST E_V$ cases.
  arXiv  Detail & Related papers  (2022-08-11T03:55:52Z)
• A first-principles calculation of electron-phonon interactions for the $\ ext{C}_2\ ext{C}_\ ext{N}$ and $\ ext{V}_\ ext{N}\ ext{N}_\ ext{B}$ defects in hexagonal boron nitride [52.77024349608834]
  Quantum emitters in two-dimensional hexagonal boron nitride (h-BN) have generated significant interest. Recent observations of Fourier transform (FT) limited photons emitted from h-BN flakes at room temperature.
  arXiv  Detail & Related papers  (2022-07-28T23:31:38Z)
• Full counting statistics of interacting lattice gases after an expansion: The role of the condensate depletion in the many-body coherence [55.41644538483948]
  We study the full counting statistics (FCS) of quantum gases in samples of thousands of interacting bosons. FCS reveals the many-body coherence from which we characterize iconic states of interacting lattice bosons.
  arXiv  Detail & Related papers  (2022-07-28T13:21:57Z)
• Prolonged orbital relaxation by locally modified phonon density of states for SiV$^-$ center in nanodiamonds [45.82374977939355]
  Coherent quantum systems are a key resource for emerging quantum technology. A novel method is presented to prolong the orbital relaxation with a locally modified phonon density of states.
  arXiv  Detail & Related papers  (2021-07-30T14:14:26Z)
• Enhanced coherence of all-nitride superconducting qubits epitaxially grown on silicon substrate [2.3180219011095327]
  We develop superconducting qubits based on NbN/AlN/NbN epitaxial Josephson junctions on silicon substrates. The all-nitride qubits have great advantages such as chemical stability against oxidation.
  arXiv  Detail & Related papers  (2021-03-13T13:03:17Z)
• Mesoscopic quantum superposition states of weakly-coupled matter-wave solitons [58.720142291102135]
  We establish quantum features of an atomic soliton Josephson junction (SJJ) device. We show that the SJJ-model in quantum domain exhibits unusual features due to its effective nonlinear strength proportional to the square of total particle number. We have shown that the obtained quantum state is more resistant to few particle losses from the condensates if tiny components of entangled Fock states are present.
  arXiv  Detail & Related papers  (2020-11-26T09:26:19Z)
• Deterministic Single Ion Implantation with 99.87% Confidence for Scalable Donor-Qubit Arrays in Silicon [44.62475518267084]
  Group-V-donor spins are attractive qubits for large-scale quantum computer devices. Group-V-donor spins implanted in an isotopically purified $28$Si crystal make them attractive qubits. We demonstrate the implantation of single low-energy (14 keV) P$+$ ions with an unprecedented $99.87pm0.02$% confidence.
  arXiv  Detail & Related papers  (2020-09-07T05:23:07Z)
• Gapless quantum spin liquid and global phase diagram of the spin-1/2 $J_1$-$J_2$ square antiferromagnetic Heisenberg model [1.2728971015881008]
  We show that the intermediate nonmagnetic phase is a gapless quantum spin liquid (QSL), whose spin-spin and dimer-dimer correlations both decay with a power law behavior. We make the first detailed comparison between the results of PEPS and the well-established density matrix renormalization group (DMRG) method through one-to-one direct benchmark for small system sizes.
  arXiv  Detail & Related papers  (2020-09-03T17:39:06Z)
• Spectral and spatial isolation of single WSe$_2$ quantum emitters using hexagonal boron nitride wrinkles [1.037769583357224]
  We create spatially and spectrally isolated quantum emitters from WSe$$ monolayers with few or no sources of emission. We show that a bilayer of hexagonal boron nitride (hBN) and WSe$$ placed on a nano substrate can be used to create and shape wrinkles that communicate local strain to the WSe$$$. We compare quantum emitters created directly on top of substrate features with quantum emitters forming along wrinkles and find that the spectra of the latter consist of mainly a single peak and a low background fluorescence.
  arXiv  Detail & Related papers  (2020-05-14T14:31:38Z)
• Anisotropy-mediated reentrant localization [62.997667081978825]
  We consider a 2d dipolar system, $d=2$, with the generalized dipole-dipole interaction $sim r-a$, and the power $a$ controlled experimentally in trapped-ion or Rydberg-atom systems. We show that the spatially homogeneous tilt $beta$ of the dipoles giving rise to the anisotropic dipole exchange leads to the non-trivial reentrant localization beyond the locator expansion.
  arXiv  Detail & Related papers  (2020-01-31T19:00:01Z)

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.