University of Cambridge > > Semiconductor Physics Group Seminars > Probing the limits of gate-based charge sensing

Probing the limits of gate-based charge sensing

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If you have a question about this talk, please contact Teri Bartlett.

Quantum computation requires a qubit-specific measurement capability to readout the final state of individual qubits. In the promising solid-state approaches based on superconducting and semiconducting nano-devices experiments are increasing in complexity and it becomes important to simplify the circuit layout and decrease the number of components. One of the components of solid-state quantum computers are the qubit readout electrometers. They are made redundant by the introduction of in-situ gate sensors based on a resonant readout. This technique couples the gate to a resonant circuit and probes the qubit’s radio-frequency polarisability. Here, we investigate the ultimate performance of such resonant readout schemes and the noise sources that limit their operation.

We find a charge sensitivity of 37 ue/\sqrt{Hz}, the best value reported for this technique, using the example of a gate-sensor strongly coupled to a double quantum dot at the corner states of a silicon nanowire transistor.

We model the charge and phase noise by solving the dynamical master equation of the fast-driven electronic transitions and determine the limits of charge and phase sensitivity of resonant readout. We find comparable performance to standard charge sensors and our model predicts limits of order ne/\sqrt{Hz} and urad/\sqrt{Hz}. We discuss the experimental factors limiting gate detection and highlight ways to optimise its sensitivity. In total, resonant gate-based detection has advantages over external electrometers not only in terms of reduced number of circuit elements, but also in terms of absolute charge sensitivity.

This talk is part of the Semiconductor Physics Group Seminars series.

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