Remote capacitive sensing in two-dimension quantum-dot arrays

We investigate gate-defined quantum dots in silicon on insulator nanowire field-effect transistors fabricated using a foundry-compatible fully-depleted silicon-on-insulator (FD-SOI) process. A series of split gates wrapped over the silicon nanowire naturally produces a $2\times n$ bilinear array of quantum dots along a single nanowire. We begin by studying the capacitive coupling of quantum dots within such a 2$\times$2 array, and then show how such couplings can be extended across two parallel silicon nanowires coupled together by shared, electrically isolated, 'floating' electrodes. With one quantum dot operating as a single-electron-box sensor, the floating gate serves to enhance the charge sensitivity range, enabling it to detect charge state transitions in a separate silicon nanowire. By comparing measurements from multiple devices we illustrate the impact of the floating gate by quantifying both the charge sensitivity decay as a function of dot-sensor separation and configuration within the dual-nanowire structure.Comment: 9 pages, 3 figures, 35 cites and supplementar

Single-electron control in a foundry-fabricated two-dimensional qubit array

Silicon spin qubits have achieved high-fidelity one- and two-qubit gates, above error correction thresholds, promising an industrial route to fault-tolerant quantum computation. A significant next step for the development of scalable multi-qubit processors is the operation of foundry-fabricated, extendable two-dimensional (2D) arrays. In gallium arsenide, 2D quantum-dot arrays recently allowed coherent spin operations and quantum simulations. In silicon, 2D arrays have been limited to transport measurements in the many-electron regime. Here, we operate a foundry-fabricated silicon 2x2 array in the few-electron regime, achieving single-electron occupation in each of the four gate-defined quantum dots, as well as reconfigurable single, double, and triple dots with tunable tunnel couplings. Pulsed-gate and gate-reflectometry techniques permit single-electron manipulation and single-shot charge readout, while the two-dimensionality allows the spatial exchange of electron pairs. The compact form factor of such arrays, whose foundry fabrication can be extended to larger 2xN arrays, along with the recent demonstration of coherent spin control and readout, paves the way for dense qubit arrays for quantum computation and simulation.Comment: 9 pages (including supplementary information and 5 figures

Pauli Blockade in a Few-Hole PMOS Double Quantum Dot limited by Spin-Orbit Interaction

We report on hole compact double quantum dots fabricated using conventional CMOS technology. We provide evidence of Pauli spin blockade in the few hole regime which is relevant to spin qubit implementations. A current dip is observed around zero magnetic field, in agreement with the expected behavior for the case of strong spin-orbit. We deduce an intradot spin relaxation rate $\approx$120\,kHz for the first holes, an important step towards a robust hole spin-orbit qubit

Switching quantum transport in a three donors silicon fin-field effect transistor

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Reflectometry of charge transitions in a silicon quadruple dot

Gate-controlled silicon quantum devices are currently moving from academic proof-of-principle studies to industrial fabrication, while increasing their complexity from single- or double-dot devices to larger arrays. We perform gate-based high-frequency reflectometry measurements on a 2x2 array of silicon quantum dots fabricated entirely using 300 mm foundry processes. Utilizing the capacitive couplings within the dot array, it is sufficient to connect only one gate electrode to one reflectometry resonator and still establish single-electron occupation in each of the four dots and detect single-electron movements with high bandwidth. A global top-gate electrode adjusts the overall tunneling times, while linear combinations of side-gate voltages yield detailed charge stability diagrams. We support our findings with $\mathbf{k}\cdot\mathbf{p}$ modeling and electrostatic simulations based on a constant interaction model, and experimentally demonstrate single-shot detection of interdot charge transitions with unity signal-to-noise ratios at bandwidths exceeding 30 kHz. Our techniques may find use in the scaling of few-dot spin-qubit devices to large-scale quantum processors.Comment: 10 pages including appendices and 7 figure