Kavli Affiliate: Menno Veldhorst
| First 5 Authors: Daniel Jirovec, Pablo Cova Fariña, Stefano Reale, Stefan D. Oosterhout, Xin Zhang
| Summary:
Coupled spins in semiconductor quantum dots are a versatile platform for
quantum computing and simulations of complex many-body phenomena. However, on
the path of scale-up, cross-talk from densely packed electrodes poses a severe
challenge. While cross-talk onto the dot potentials is nowadays routinely
compensated for, cross-talk on the exchange interaction is much more difficult
to tackle because it is not always directly measurable. Here we propose and
implement a way of characterizing and compensating cross-talk on adjacent
exchange interactions by following the singlet-triplet avoided crossing in Ge.
We show that we can easily identify the barrier-to-barrier cross-talk element
without knowledge of the particular exchange value in a 2×4 quantum dot array.
We uncover striking differences among these cross-talk elements which can be
linked to the geometry of the device and the barrier gate fan-out. We validate
the methodology by tuning up four-spin Heisenberg chains. The same methodology
should be applicable to longer chains of spins and to other semiconductor
platforms in which mixing of the singlet and the lowest-energy triplet is
present or can be engineered. Additionally, this procedure is well suited for
automated tuning routines as we obtain a stand-out feature that can be easily
tracked and directly returns the magnitude of the cross-talk.
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