This February, researchers from TU Delft (QuTech) and the Madrid Institute of Materials Science (ICMM-CSIC) reported a major milestone: they demonstrated a way to read out the hidden state of a Majorana-based qubit with a single measurement, without relying on a local probe that would “miss” the information by design.
Why Majorana qubits are different (and why they’re hard to read)
In a conventional qubit, information tends to be tied to a local property, something you can probe at a point. Majorana-based (topological) approaches aim for something smarter: encode quantum information in the shared “parity” of two linked quantum modes (Majorana zero modes). That distributed encoding is what makes them naturally more resistant to local disturbances.
But that same strength becomes an experimental catch-22:
- If the information is non-local, a local charge sensor won’t reliably “see” it.
- So the big question has been: how do you measure a property that doesn’t live in one spot?
- The breakthrough: a “global probe” that can read parity in one shot
The teams addressed this by building a carefully engineered device sometimes described as a minimal Kitaev chain: two semiconductor quantum dots coupled via a superconductor, assembled in a modular, bottom-up way.
Then they applied a readout technique based on quantum capacitance, a measurement that acts like a global probe of the system’s overall state. With it, they could determine the parity (even/odd) of the two coupled Majorana modes in real time with a single-shot measurement, observed as random telegraph switching.
Even more encouraging: by analyzing these parity “jumps,” the researchers report parity coherence lifetimes exceeding one millisecond, a meaningful signal that the encoded information is holding up long enough to be operationally interesting.
What this changes for the path to robust quantum machines
This result doesn’t instantly deliver a fault-tolerant quantum computer, but it removes a long-standing bottleneck: readout. If topological qubits are to be practical, we need reliable ways to prepare, control, and measure their protected states.
This work demonstrates a readout route that is aligned with the core promise of Majorana-based hardware:
- Keep information non-local for protection
- Use a non-local measurement to access it
In other words, it’s a step toward quantum systems that keep their results intact in the real world.
Why this matters for Belgium’s quantum future
At Quantum Circle, we care about breakthroughs like this because they shape the roadmap for real-world impact, and they help Belgium’s ecosystem decide where to build capability next.
This story touches all five Quantum Circle workgroups:
- Technology: new measurement techniques (quantum capacitance readout) and device architectures for scalable platforms.
- Research: tighter loops between theory and experiment, exactly what accelerates credibility and adoption.
- Business: more stable qubits change the calculus for timelines, partnerships, and industrial use cases.
- Ecosystems: Europe-wide collaboration (Delft–Madrid) is a template for how ecosystems win: by connecting strengths, not duplicating efforts.
- Society: “robustness by design” is not just a technical detail, it’s how we move from lab prototypes to trustworthy systems.
Belgium is well-positioned to plug into this momentum, by translating foundational advances into engineering talent, supply-chain readiness, and use-case co-creation across industry and public stakeholders.
