arXiv subjects

Talise Oh

Publications and source records attributed to Talise Oh.

4 recordsLinked to original sources

arXiv2026

Depth-Resolved Lattice Distortions in a Silicon-Germanium Qubit Host

Semiconductor qubits, promising for quantum computation, inherit properties from their host lattice. Quantum dot spins, occupying the local lowest energy states in the conduction band, necessarily couple to structural disorder and interfaces. While silicon-based systems promise low noise alongside industrially compatible manufacturing, the growth of SiGe---a leading platform---unavoidably introduces lattice dislocations, inhomogeneous strain, and crosshatch patterns, expected to cause fluctuations between devices, qubit failure, and subsequently higher operational overhead. Through X-ray nano-structural mapping of an Intel Si/SiGe chip, we reveal, with 30$~$nm lateral and 200$~$nm functional depth resolution, how extended lattice defects introduced during growth propagate through the heterostructure, creating permanently distorted lattice planes and strain. We correlate these at the $\approx1~\mu$m scale of a quantum dot device and calculate the impact on qubit energy spectra. We observe crosshatch fine structure and find that substrate miscut and growth correlate with the final crosshatch pattern.

cond-mat.mes-hall↗

arXiv2025

Valley Splitting Correlations Across a Silicon Quantum Well Containing Germanium

Quantum dots in SiGe/Si/SiGe heterostructures host coherent electron spin qubits, which are promising for future quantum computers. The silicon quantum well hosts near-degenerate electron valley states, creating a low-lying excited state that is known to reduce spin qubit readout and control fidelity. The valley energy splitting is dominated by the microscopic disorder in the SiGe alloy and at the Si/SiGe interfaces, and while Si devices are compatible with large-scale semiconductor manufacturing, achieving a uniformly large valley splitting energy across a many-qubit device spanning mesoscopic distances is an outstanding challenge. In this work we study valley splitting variations in a 1D quantum dot array, formed in a Si$_{0.972}$Ge$_{0.028}$ quantum well, manufactured by Intel. We observe correlations in valley splitting, at both sub-100nm (single gate) and >1$\mu$m (device) lengthscales, that are consistent with alloy disorder-dominated theory and simulation. Our results develop the mesoscopic understanding of Si/SiGe heterostructures necessary for scalable device design.

cond-mat.mes-hall↗

arXiv2023

Reducing strain fluctuations in quantum dot devices by gate-layer stacking

Nanofabricated metal gate electrodes are commonly used to confine and control electrons in electrostatically defined quantum dots. However, these same gates impart strain-induced potential fluctuations that can potentially impair device functionality. Here we investigate strain fluctuations in Si/SiGe heterostructures, caused by (i) lattice mismatch, (ii) materials-dependent thermal contraction, and (iii) depositional stress in the metal gates. By simulating gate geometries, ranging from simple to realistically complicated, we identify two opposing effects in overlapping gate structures: (a) gate-driven behavior arising from isolated gates vs (b) oxide-driven behavior arising from the thin oxides separating the gates in an overlapping geometry. These limiting behaviors induce strains of opposite sign, pointing towards the possibility of suppressing strain fluctuations through careful design. Here, we demonstrate nearly total suppression of short-range strain fluctuation through device optimization. These results suggest that strain fluctuations should not pose an insurmountable challenge to qubit uniformity, provided that oxide and overlapping gate thicknesses can be tuned.

cond-mat.mes-hall↗

arXiv2023

Probing Lepton Flavor Violation at Circular Electron-Positron Colliders

Lepton flavor violation is one of the cleanest probes of physics beyond the standard model. In this work, we explore the sensitivity of the process $e^+ e^- \to \tau \mu$ to new physics above the TeV scale at the proposed circular electron-positron colliders FCC-ee and CEPC. We compute the $e^+ e^- \to \tau \mu$ cross-section in the Standard Model Effective Field Theory and assess the relevant backgrounds. We compare our sensitivity projections to existing and expected constraints from tau decays and $Z$ decays and find that the future electron-positron colliders provide competitive probes of new physics. We highlight the complementarity of searches for resonant $e^+ e^- \to Z \to \tau \mu$ production on the $Z$ pole and searches for non-resonant $e^+ e^- \to \tau \mu$ at higher center-of-mass energies.

hep-ph↗