published-canonicalconceptmaha-epistemic/1.0

Transmon qubit

The transmon is a design regime of the Cooper-pair-box circuit. This record separates the published circuit model from later claims about coherence, scaling, error correction, fabrication yield, and commercial readiness.

Bounded definition

A superconducting qubit design that trades a weak reduction in anharmonicity for an exponential reduction in charge dispersion as the Josephson-to-charging-energy ratio increases.

What the model establishes

The transmon retains the Cooper-pair-box circuit but operates it in a different energy regime. The published analysis shows why charge sensitivity can fall much faster than the circuit loses the anharmonicity required to address transitions selectively.

This is a precise design relationship, not a general declaration that every transmon implementation has long coherence or that a transmon processor is fault tolerant.

Claims: urn:maha:claim:transmon-energy-ratio

What must be measured separately

A physical system still requires device-specific measurements of relaxation, dephasing, leakage, gate fidelity, crosstalk, calibration drift, packaging, cryogenic control, fabrication variation, and logical performance.

Those measurements belong in additional records with their own devices, methods, dates, uncertainty, and replication assessments.

Claim ledger

Every proposition keeps its own evidence state.

theoretical-modelsingle-study

In the transmon design analysed by Koch and colleagues, increasing the ratio of Josephson energy to charging energy suppresses charge dispersion exponentially while anharmonicity decreases only by a weak power law.

Scope
Circuit quantization and numerical analysis of the transmon regime described in the 2007 Physical Review A paper.
Boundary
The model does not by itself establish a fabrication yield, device lifetime, logical error rate, system-scale advantage, or commercially useful fault-tolerant computer.
Uncertainty
The relationship is model- and parameter-dependent; this Phase 1 record does not reproduce a numerical device-specific uncertainty interval.
Replication
Independent experimental implementations are outside this bounded source record and are not counted here.

Primary sources

Citation, locator, rights, and boundary travel together.

  1. Source 1 · Physical Review A, American Physical Society

    Charge-insensitive qubit design derived from the Cooper pair box

    Jens Koch, Terri M. Yu, Jay Gambetta, A. A. Houck, D. I. Schuster, et al.

    Exact locator
    Abstract; Sections II–IV; equations and numerical analysis defining the transmon regime.
    Establishes
    The source introduces and analyses the transmon circuit regime, including the different scaling of charge dispersion and anharmonicity with the Josephson-to-charging-energy ratio.
    Boundary
    It is a design and modelling paper, not proof of later processor-scale fault tolerance, manufacturing economics, or strategic advantage.
    Rights basis
    citation with paraphrase · The Maha page provides original summary and boundary language and links to the publisher record; no article passage is reproduced.