Single-shot parity readout of a minimal Kitaev chain
Article metadata
Article Date: 11 February 2026
Article URL: https://www.nature.com/articles/s41586-025-09927-7
Article Title: Single-shot parity readout of a minimal Kitaev chain
Article Image: (not provided)
Summary
The authors demonstrate single-shot fermion-parity readout of a minimal Kitaev chain realised with two quantum dots coupled to a proximitised InSb nanowire segment. Using fast RF reflectometry (quantum-capacitance readout) and a nearby charge sensor, they resolve parity states in real time, measure parity lifetimes and map the regimes where elastic cotunnelling (ECT) and crossed Andreev reflection (CAR) balance (the PMM “sweet spot”, t ≈ Δ). Time-trace analysis yields millisecond-scale switching times (average switching time ≈ 1.5 ms), and the team shows parity readout for two coupled minimal chains in a qubit-like geometry. Data and code are available via a linked DOI.
Key Points
- Single-shot parity readout achieved for a minimal Kitaev chain implemented with quantum dots coupled to a superconducting InSb nanowire.
- Readout methods: quantum-capacitance (RF reflectometry) on a resonator and fast charge sensing via a nearby quantum dot; both used to detect parity switching as telegraph noise.
- Identification of a PMM (poor man’s Majorana) sweet spot where ECT and CAR balance (t ≈ Δ), enabling clear parity-dependent signals.
- Measured parity dynamics: switching processes are Poissonian with average switching time ~1.5 ms (from PSD fit) and parity lifetimes extracted from time-trace analyses.
- Demonstration extended to two minimal chains coupled to a common superconductor, resolving the four-parity manifold in a qubit geometry and showing single-shot readout in the |ee⟩, |oo⟩ computational basis.
- Data and analysis code are publicly available (DOI: 10.4121/227fd419-fded-4a96-ab62-421a0cd57fa5.v3).
- Work highlights practical parity-readout routes relevant for developing parity-based qubits, though global protection remains limited (zero-bias peaks split under global perturbations).
Content summary
The experiment uses an InSb nanowire with an aluminium proximitised segment and two gate-defined quantum dots to form a minimal Kitaev chain. RF reflectometry on an off-chip resonator measures quantum capacitance changes that depend on the system parity; a nearby charge sensor (CS) provides complementary single-lead reflectometry. By tuning a hybrid gate (V_H) the authors sweep between regimes dominated by CAR or ECT and locate the PMM sweet spot where t ≈ Δ. At that point, parity readout contrast is maximal and charge-sensor insensitivity lines up with the predicted behaviour.
Time traces were recorded with microsecond-to-millisecond integration times and analysed with hidden Markov models, Gaussian-mixture fits and PSD fitting to extract signal-to-noise ratios, parity polarisation maps and switching rates. The reported switching behaviour is consistent with Poissonian events and shows parity lifetimes that make single-shot readout feasible on millisecond timescales. The team also fabricates a device containing two minimal chains, demonstrates multi-level single-shot signals consistent with |ee⟩ and |oo⟩ states, and extracts transition rates with no evidence of direct inter-chain tunnelling.
Context and relevance
This paper is a concrete step on the path from demonstrations of Majorana-like signatures to practical parity readout suitable for parity-based qubits. Fast, single-shot parity measurement is a necessary tool for parity-qubit operation, measurement-only protocols and teleportation-style schemes that use Majorana zero modes. Although the system studied is a “poor man’s” Majorana realisation (so not topologically protected in the strict sense), the ability to read parity in single shots and to measure lifetimes and error rates is essential for assessing viability of parity-based qubits and for developing control/readout techniques that scale.
The methods (quantum-capacitance RF reflectometry and proximal charge sensing) are broadly relevant for experimental groups working on hybrid superconductor–semiconductor devices, Andreev-molecule physics and semiconductor quantum-dot networks intended for topological/quasiparticle-protected architectures. The public data and code release improves reproducibility and enables further analysis by the community.
Why should I read this?
Short and blunt: if you care about Majorana parity readout or parity-based qubits, this is the paper you skim first. It shows single-shot parity detection, gives realistic parity lifetimes, and even tries a two-chain qubit geometry — all with data and code you can grab and poke. Saves you time and tells you what works (and what still needs work).
Author note (style)
Punchy, experimental advance with clear takeaways: single-shot parity readout is now demonstrated in a minimal Kitaev-chain platform and the paper quantifies the readout performance and parity dynamics — essential reading for experimentalists and device designers in the Majorana/qubit space.