Electron cascade for distant spin readout

Cornelis J Van Diepen,Lieven M K Vandersypen,Christian Reichl,Tzu-Kan Hsiao,Uditendu Mukhopadhyay,Werner Wegscheider

doi:10.1038/s41467-020-20388-6

Cornelis J Van Diepen, Lieven M K Vandersypen + Show 4 more

Open Access

https://doi.org/10.1038/s41467-020-20388-6

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Abstract

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes. A cascade can transmit information along a quantum dot array over a distance that extends by far the effect of the direct Coulomb repulsion. We demonstrate that a cascade of electrons can be combined with Pauli spin blockade to read out distant spins and show results with potential for high fidelity using a remote charge sensor in a quadruple quantum dot device. We implement and analyse several operating modes for cascades and analyse their scaling behaviour. We also discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. The high connectivity of such arrays greatly improves the capabilities of quantum dot systems for quantum computation and simulation.

Highlights

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation
A cascade can be implemented in various quantum dot array layouts
The quantum dots are filled in a chequerboard manner, compatible with the proposal in ref. 4, and the sensor is placed at the periphery of the two-dimensional array, with sufficient space for reservoirs

Summary

Introduction

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. We discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. 1234567890():,; Fault-tolerant quantum computation benefits from high connectivity, and requires fast and high-fidelity readout[1]. Qubit connectivity and density are severely limited when charge sensors need to be placed near all quantum dots in the qubit array. Readout based on shuttling[13] requires paths of empty dots to avoid that qubits are lost into the reservoirs, and the long-distance movement of electrons breaks qubit connectivity. We show that charge information can be transferred along a quantum dot array with a cascade, in which the spin-dependent movement of one electron induces the subsequent movement of other electrons. A cascade has been used to build classical logic with molecules in scanning-tunnelling microscopes[20] and with excess electrons in cellular automata based on Al islands[21,22]

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