December 8, 2022

Microsoft chooses exotic “topological qubits”

Microsoft chooses exotic “topological qubits”

Microsoft Research announced a major breakthrough in its quantum computing pursuit — the foundation for a new type of qubit, one which had never left the world of theory before… and still hasn’t.

Microsoft ultimately still hasn’t produced devices based on its new qubit design but is adding credence to their feasibility with proofs produced by immense simulations within and without Microsoft’s Azure Quantum cloud infrastructure.

Microsoft’s research into quantum computing focuses on a special, exotic type of qubits, topological qubits, that it has touted as its vehicle into the future of quantum since 2016.

Microsoft is not only demonstrating that topological qubits are on the verge of becoming a reality: the company says they are ultimately the only currently valid bet for sustainable, scalable (to the tune of millions of harnessed qubits), and ultimately meaningful quantum computing.

The first thing to remember about topological qubits is that they still haven’t materialized. Instead, they are theorized to exist as pairs of Majorana zero modes (MZMs), a special type of quasiparticle that naturally behaves as if it were only half of an electron. These MZMs have been shown to deposit as a layer on the surface of superconducting materials, and showcase extreme resilience to environmental noise (such as heat, stray subatomic particles or magnetic fields). Left unchecked, or not engineered against, this environmental noise leads to decoherence — the process by which qubits fall out of their superposition state and reveal their value. When qubits reveal their value too early, an error appears before the calculation is finished.

Microsoft’s topological qubit design features a U-shaped wire with a Majorana zero mode at each end, thus providing physical separation, in proximity to a quantum dot. This quantum dot serves as a control mechanism because its capacitance changes whenever it interacts with either of the Majorana zero modes, which allows it to be measured. This is the part Microsoft still hasn’t figured out: its design still hasn’t incorporated a quantum dot.

The resilience of topological qubits comes from the fact that both MZMs (in Microsoft’s design, at each end of the U-shaped wire) are responsible for encoding the quantum information. However, because the information is only reachable by looking at both quasiparticles’ states simultaneously, the qubit’s state doesn’t decohere unless both MZMs are equally affected and “forced” to reveal their contents. And depending on the engineering design, researchers can provide a measure of distance between the MZMs, creating a gap between them that reduces the chance of both particles decohering. (Tom’s Hardware)

Read more with the excellent article of Tom’s Hardware website.