As the fundamental flaw of today’s quantum computers, improving qubit stability remains the focus of much research in this field. One such stability attempt involves so-called topological quantum computing with the use of anyons, which are two-dimensional quasiparticles. Such an approach has been claimed by Microsoft in a recent paper in Nature. This comes a few years after an earlier claim by Microsoft for much the same feat, which was found to be based on faulty science and hence retracted.

The claimed creation of anyons here involves Majorana fermions, which differ from the much more typical Dirac fermions. These Majorana fermions are bound with other such fermions as a Majorana zero mode (MZM), forming anyons that are intertwined (braided) to form what are in effect logic gates. In the Nature paper the Microsoft researchers demonstrate a superconducting indium-arsenide (InAs) nanowire-based device featuring a read-out circuit  (quantum dot interferometer) with the capacitance of one of the quantum dots said to vary in a way that suggests that the nanowire device-under-test demonstrates the presence of MZMs at either end of the wire.

Microsoft has a dedicated website to their quantum computing efforts, though it remains essential to stress that this is not a confirmation until their research is replicated by independent researchers. If confirmed, MZMs could provide a way to create more reliable quantum computing circuitry that does not have to lean so heavily on error correction to get any usable output. Other, competing efforts here include such things as hybrid mechanical qubits and antimony-based qubits that should be more stable owing to their eight spin configurations.

One of the problems with quantum bits, or “qubits”, is that they tend to be rather fragile, with a high sensitivity to external influences. Much of this is due to the atoms used for qubits having two distinct spin states of up or down, along with the superposition. Any disturbing of the qubit’s state can cause it to flip between either spin, erasing the original state. Now antimony is suggested as a better qubit atom by researchers at the University of New South Wales in Australia due to it having effectively eight spin states, as also detailed in the university press release along with a very tortured ‘cats have nine lives’ analogy.

For the experiment, also published in Nature Physics, the researchers doped a silicon semiconductor with a single antimony atom, proving that such an antimony qubit device can be manufactured, with the process scalable to arrays of such qubits. For the constructed device, the spin state is controlled via a transistor constructed on top of the trapped atom. As a next step a device with closely spaced antimony atoms will be produced, which should enable these to cooperate as qubits and perform calculations.

By having the qubit go through many more states to fully flip, these qubits can potentially be much more stable than contemporary qubits. That said, there’s still a lot more research and development to be done before a quantum processor based this technology can go toe-to-toe with a Commodore 64 to show off the Quantum Processor Advantage. Very likely we’ll be seeing more of IBM’s hybrid classical-quantum systems before that.