A quantum dot is a tiny structure, only a few tens of nanometres across, that traps individual electrons inside a semiconductor. The confinement is so tight that the electron’s energy levels become discrete, much like those of an atom. For this reason, quantum dots are sometimes described as artificial atoms, with the important advantage that engineers can design and position them on a chip.
In a silicon spin qubit processor, quantum dots are the physical home of the qubit. Voltages applied to nanoscale gate electrodes shape the electrostatic landscape, drawing a single electron into the dot and holding it there. The spin of that confined electron encodes the quantum information, while neighbouring dots can be tuned to interact and create entanglement.
Because quantum dots can be formed using the same gate structures found in conventional transistors, they can be manufactured with established CMOS processes. This is central to Quantum Motion’s approach. Building qubits from quantum dots on industry-standard silicon wafers means the density and manufacturing maturity of the semiconductor industry can be applied directly to the challenge of scaling quantum processors.