Building qubits with topoconductors
The topoconductor differs from standard superconductors in the way it hosts qubits. Like standard superconductors, the topoconductor provides a zero-resistance path for Cooper pairs of electrons. Unlike standard superconductors, the topoconductor allows an unpaired electron to exist. This is how the topoconductor sets its quantum state and how that state is measured. With an unpaired electron, the topoconductor has a charge (and different superposition states will have different charges). At the same time, there’s no way to trap that electron, as it’s everywhere in the topoconductor at the same time.
The single qubit building block is called a tetron. It has two superconducting topological wires that host four Majorana Zero Modes (MZM) at each end. The wires are linked by a thinner superconductor. Together with the wire, these four MZMs control and store the state of the qubit. The topological wire is coupled to a pair of quantum dots, which have a different charge depending on the state of the qubit.
This charge is what the microwave detectors measure. The process is extremely accurate, with an extremely low probability of error. However, the extremely low probability of error still isn’t low enough, and there needs to be better error correction for Microsoft to deliver a working quantum computer. This is why the device road map goes up to multi-tetron devices that provide only a handful of qubits. Despite this, Majorana 1-based devices will need only one-tenth of the error-correction hardware of comparable quantum computers.
