Stuff that is really really really small behaves in weird and cool ways. We can sort of tell how it works, but it's really hard to do anything with it because it is so small. These smart people found a new way of working with really small stuff that could maybe one day be used to build a new type of computers.
It's an implementation of a single qubit, tested through several transformations (one of two critical parts of a quantum computer) using a quantum dot. A useful qubit can be placed into a superposition state, say with a probability, on measurement, of being found up or down. A quantum dot is an area of a semiconductor that acts like an atom, but doesn't have a nucleus. The paper focuses on a novel implementation where the electron of interest is in a higher shell than other implementations, and quantifies the performance, finding higher shell electrons perform better than lower ones.
Finally they claim they may be able to implement coherent entanglement (the other critical ingredient for quantum computing) but it is only mentioned as a foot note, with a nod to another paper which analyzed quantum dot electron spin qubits under entanglement, but not with the higher shells.
