  Even as today's most prominent spin-based qubit technologies are maturing in
terms of capability and sophistication, there is growing interest in exploring
alternate material platforms that may provide advantages, such as enhanced
qubit control, longer coherence times, and improved extensibility. Recent
advances in heterostructure material growth have opened new possibilities for
employing hole spins in semiconductors for qubit applications. Undoped,
strained Ge/SiGe quantum wells are promising candidate hosts for hole
spin-based qubits due to their low disorder, large intrinsic spin-orbit
coupling strength, and absence of valley states. Here, we use a simple
one-layer gated device structure to demonstrate both a single quantum dot as
well as coupling between two adjacent quantum dots. The hole effective mass in
these undoped structures, $m$* ~ 0.08 $m$$_0$, is significantly lower than for
electrons in Si/SiGe, pointing to the possibility of enhanced tunnel couplings
in quantum dots and favorable qubit-qubit interactions in an
industry-compatible semiconductor platform.
