They combined single-spin qubit called a Loss-DiVincenzo qubit and a singlet-triplet qubit.

The Loss-DiVincenzo qubit has very high control fidelity—meaning that it is in a clear state, making it ideal for calculations, and has a long decoherence time. It will stay in a given state for a relatively long time before losing its signal to the environment. Unfortunately, the downside to these qubits is that they cannot be quickly initialized into a state or read out.

The singlet-triplet qubit is quickly initialized and read out, but it quickly becomes decoherent. They combined the two types with a type of quantum gate known as a controlled phase gate, which allowed spin states to be entangled between the qubits in a time fast enough to maintain the coherence, allowing the state of the single-spin qubit to be read out by the fast singlet-triplet qubit measurement.