Measurements of capacitive coupling within a quadruple quantum dot array

Abstract

We present measurements of the capacitive coupling energy and the inter-dot capacitances in a linear quadruple quantum dot array in undoped Si/SiGe. With the device tuned to a regime of strong ($>$1 GHz) intra-double dot tunnel coupling, as is typical for double dot qubits, we measure a capacitive coupling energy of $20.9\pm 0.3$ GHz. In this regime, we demonstrate a fitting procedure to extract all the parameters in the 4D Hamiltonian for two capacitively coupled charge qubits from a 2D slice through the quadruple dot charge stability diagram. We also investigate the tunability of the capacitive coupling energy, using inter-dot barrier gate voltages to tune the inter- and intra-double dot capacitances, and change the capacitive coupling energy of the double dots over a range of 15-32 GHz. We provide a model for the capacitive coupling energy based on the electrostatics of a network of charge nodes joined by capacitors, which shows how the coupling energy should depend on inter-double dot and intra-double dot capacitances in the network, and find that the expected trends agree well with the measurements of coupling energy.

6 pages + supplementary information, 4 figures

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• Programmable two-qubit gates in capacitively coupled flopping-mode spin qubits
• Crosstalk analysis for simultaneously driven two-qubit gates in spin qubit arrays
• Single-shot readout of multiple donor electron spins with a gate-based sensor
• Anisotropy with respect to the applied magnetic field of spin qubit decoherence times
• Probing two-qubit capacitive interactions beyond bilinear regime using dual Hamiltonian parameter estimations
• QDarts: A Quantum Dot Array Transition Simulator for finding charge transitions in the presence of finite tunnel couplings, non-constant charging energies and sensor dots
• Resonator-mediated quantum gate between distant charge qubits
• Sign-switching of superexchange mediated by few electrons under non-uniform magnetic field
• Two-qubit sweet spots for capacitively coupled exchange-only spin qubits
• Universal control of superexchange in linear triple quantum dots with an empty mediator
• Exploring Entanglement Spectrum and Phase Diagram in multi-electron Quantum Dot Chains