  The small size and excellent integrability of silicon
metal-oxide-semiconductor (SiMOS) quantum dot spin qubits make them an
attractive system for mass-manufacturable, scaled-up quantum processors.
Furthermore, classical control electronics can be integrated on-chip,
in-between the qubits, if an architecture with sparse arrays of qubits is
chosen. In such an architecture qubits are either transported across the chip
via shuttling, or coupled via mediating quantum systems over
short-to-intermediate distances. This paper investigates the charge and spin
characteristics of an elongated quantum dot -- a so-called jellybean quantum
dot -- for the prospects of acting as a qubit-qubit coupler. Charge transport,
charge sensing and magneto-spectroscopy measurements are performed on a SiMOS
quantum dot device at mK temperature, and compared to Hartree-Fock
multi-electron simulations. At low electron occupancies where disorder effects
and strong electron-electron interaction dominate over the electrostatic
confinement potential, the data reveals the formation of three coupled dots,
akin to a tunable, artificial molecule. One dot is formed centrally under the
gate and two are formed at the edges. At high electron occupancies, these dots
merge into one large dot with well-defined spin states, verifying that
jellybean dots have the potential to be used as qubit couplers in future
quantum computing architectures.
