#topologicalcore

Microsoft Majorana Zero Modes

Topological qubits offer a promising, if arduous, path to quantum computing since they are potentially error-resistant. Topological qubits are intrinsically stable because quantum information is encoded to shelter it from local disturbances, unlike conventional qubits, which are highly susceptible to noise and environmental disturbances. They're strong because they use exotic quantum excitations from nonabelian anyons in two-dimensional materials, which would need a fundamental change in how they're "braided."

Stability is sought in topological qubits because it may simplify quantum error correction (QEC) for a practical quantum computer.

Majorana Zero Modes (MZMs)

MS's topological qubit scheme relies on Majorana Zero Modes. Microsoft claims their “topoconductor” can make and regulate quasiparticles, which were only discovered in textbooks for almost a century. MZMs, particle-like collective excitations, are expected to form at superconductor frontiers. The fundamental components of Microsoft's qubits store quantum information by identifying if a wire has odd or even electrons. Topoconductor exchanges an unpaired electron between two MZMs, making it “invisible to the environment” and protecting quantum information, unlike typical superconductors, which require energy.

Majorana 1, Microsoft's first Quantum Processing Unit (QPU) driven by a “Topological Core,” is one of their latest innovations. This core enables single-chip scaling to a million qubits.

This “topological superconductivity,” made feasible by Microsoft's discoveries in gate-defined devices combining indium arsenide and aluminium, is called the “topoconductor” material. After cooling to almost zero and magnetic field adjustment, these devices form topological superconducting nanowires with MZMs at their ends.

Microsoft’s roadmap centres on the “tetron,” a single-qubit device with two parallel topological wires and a MZM at each end, connected by a trivial superconducting wire perpendicular to the wire. MZMs should appear at this H-shaped structure's four ends.

Microsoft has developed a new method for reading quantum information from well-hidden MZMs and manipulating qubit state.

Measurement Process: Digital switches connect both nanowire ends to a quantum dot, a small semiconductor device that stores electrical charge. Critically, nanowire parity determines the dot's charge retention increase. Microwaves sense this shift and imprint the nanowire's quantum states on the dot based on charge maintenance.

After preliminary testing showed a 1% error rate for this single-shot assessment, Microsoft identified areas for lowering. The system had a remarkable stability, with only one state flip per millisecond due to external energy breaking Cooper pairs rarely.

Microsoft completed Pauli-X and Z measurements, which use single-shot interferometric measurements of fermion parity for two loops inside the tetron structure. The Pauli-Z measurement uses a second fermion parity measurement in a loop with MZMs, while the Pauli-X measurement uses two points in a loop with two MZMs. The initial performance metrics for parity changes were τX = 14.5 ± 0.3µs and τZ = 12.4 ± 0.4ms, with 16% assignment errors for X and 0.5% for Z measurements. These measurements help Microsoft create its measurement-based quantum computer because they demonstrate measurement-based control.

This measurement-based technology simplifies QEC and changes quantum control. Because error correction uses digital pulses to join and detach quantum dots from nanowires rather than complex analogue control signals, large numbers of qubits may be controlled efficiently.

Microsoft wants a systematic approach to scalable QEC. A 4x2 tetron array will demonstrate measurement-based braiding transformations and entanglement with a two-qubit subset in future phases. Quantum error detection on two logical qubits will be implemented using the entire eight-qubit array.

They say their QEC codes cut overhead tenfold over previous methods. In the final phase of the Underexplored Systems for Utility-Scale Quantum Computing (US2QC) initiative, DARPA has selected Microsoft to build a fault-tolerant topological qubit prototype “in years, not decades”.

Challenges & Community Review:

Despite Microsoft's assurances, several quantumists remain unconvinced.

Microsoft had a study published in Nature, but the editorial team stated that the findings “do not represent evidence for the presence of Majorana zero modes” in the devices studied. One reason for this caution is that Microsoft reversed a 2018 claim about experimental Majorana zero modes.

“Topological Gap Protocol” Issues: In March 2025, Chetan Nayak presented fresh tetron qubit data at the APS Global Physics Summit. Henry Legg of the University of St Andrews said Microsoft's “topological gap protocol (TGP)” used to establish MZMs is “flawed” and likely to produce “false positives.” Microsoft's Roman Lutchyn said the TGP may create false positives, but the chance is low.

Noisy X Measurements: Nayak admitted that loud X measurements were not “visible with the naked eye” yet used them to prove quantum superpositions. Due to the noise, scientists like Javad Shabani and Eun-Ah Kim questioned whether the data showed qubit activity. Shabani added, “They can’t control it, but it might be a qubit.

Scalability and Timeline: Aaronson says the topological qubit is “Not yet!” useful for accelerating computation since commercial practicality requires scaling to dozens or millions of reliable qubits. He calls Microsoft's “few years” fault-tolerant prototype plan “overly aggressive”.

Alternative Strategies: Google and IBM focus on superconducting qubits or trapped ions, which have seen more experimental progress, while Microsoft is one of the few major computer companies studying topological qubits.