Extracting inter-dot tunnel couplings between few donor quantum dots in silicon

Abstract

The long term scaling prospects for solid-state quantum computing architectures relies heavily on the ability to simply and reliably measure and control the coherent electron interaction strength, known as the tunnel coupling, $t_c$. Here, we describe a method to extract the $t_c$ between two quantum dots (QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few donor triple QD tunnel coupled to a nearby single-electron transistor (SET) in silicon. The device was patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct measurement of the tunnel coupling for a given inter-dot distance. We extract $t_{\mathrm{c}}=5.5\pm 1.8\mathrm{GHz}$ and $t_{\mathrm{c}}=2.2\pm 1.3\mathrm{GHz}$ between each of the nearest-neighbour QDs which are separated by 14.5 nm and 14.0 nm, respectively. The technique allows for an accurate measurement of $t_c$ for nanoscale devices even when it is smaller than the electron temperature and is an ideal characterisation tool for multi-dot systems with a charge sensor.

arXiv comment6 pages, 4 figures

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• Coupling MOS Quantum Dot and Phosphorus Donor Qubit Systems