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Tim J. Wilson

Publications and source records attributed to Tim J. Wilson.

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Rapid Charge Stability Diagram Generation from Device-level Modeling of Semiconductor Quantum Dots

Self-consistent Schr\"odinger-Poisson calculations are a powerful tool for predicting the behavior of layered semiconductor quantum dot devices. However, characterization of charge stability diagrams through fully simulated gate-voltage sweeps is computationally expensive. Combining a Multi-Domain Multi-Model (MDMM) approach with an automated tuning routine, we identify gate voltages associated with selected charge configurations. This small set of self-consistent simulations can be augmented with Full Configuration Interaction (FCI) energy calculations to extract charging energies, lever arms, and interdot Coulomb interactions to directly parameterize a Hubbard model for rapid charge stability diagram generation. For an Intel Tunnel Falls Si/SiGe device, we demonstrate the Hubbard model's ability to reproduce charge stability diagrams at a fraction of the computational cost in comparison to voltage bias sweeps. We further compare the simulated diagrams to experimental data and demonstrate qualitative agreement. Our result represents a step towards predictive digital twin models for semiconductor quantum dot devices. Finally, we apply this workflow towards lever arm engineering in a second device, demonstrating that the method extends to multiple architectures.

cond-mat.mes-hall

Real-Time FPGA-Based Multi-Parameter Feedback Stabilization of a Silicon Double Quantum Dot

Long term operation of semiconductor spin qubits requires active stabilization of quantum dot potentials against low-frequency charge noise. Previous work demonstrated a gradient-descent feedback (GDFB) approach on a silicon double quantum dot utilizing transport current measurements. We extend such a GDFB approach in a silicon double quantum dot device with high-bandwidth rf-reflectometry readout by utilizing a field-programmable gate array, the OPX by Quantum Machines, for digital signal processing. The OPX enables continuous multi-parameter gradient calculation and quick gate voltage updates, significantly increasing the effective feedback bandwidth compared to previous work. By operating with 8 steps per feedback cycle and an integration time of 25.6 $\mu$s, this high speed stabilization scheme achieves a -6 dB noise suppression up to a bandwidth of 5 kHz. This effectively suppresses low frequency 1/f noise, maintaining device stability over longer time periods, and potentially enables real-time control in large-scale quantum dot arrays.

cond-mat.mes-hall

Fast and Sensitive Readout of a Semiconductor Quantum Dot Using an In-Situ Microwave Resonator with Enhanced Gate Lever Arm

We report an experimental study of a Si/SiGe double quantum dot (DQD) directly coupled to a niobium superconducting coplanar stripline (CPS) microwave resonator. This hybrid architecture enables high-bandwidth dispersive readout suitable for real-time feedback and error-correction protocols. Fast and sensitive readout is achieved primarily by optimizing the DQD gate lever arm, guided by MaSQE quantum dot simulations, which enhances the dispersive signal without requiring high-impedance resonators. We demonstrate a signal-to-noise ratio (SNR) of unity with an integration time of 34.54 nanoseconds, corresponding to a system bandwidth of 14.48 MHz and a charge sensitivity of 0.000186 e per square root hertz. Analysis of the voltage power spectral density (PSD) of the in-phase (I) and quadrature (Q) baseband signals characterizes the system's readout noise, with the PSD's dependence on integration time providing insight into distinct physical regimes.

cond-mat.mes-hall