REVIEW 3 major objections 2 minor
A finite optimal operating temperature minimizes total power for industry-compatible silicon spin quantum computers; colder is not always better.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · grok-4.5
2026-07-14 02:43 UTC pith:RXJABWRL
load-bearing objection Clean system-level claim from temperature-dependent GST plus a power model, but the abstract alone cannot support the large-scale optimum. the 3 major comments →
Optimal operating temperature for industry-compatible silicon spin quantum computing: colder is not necessarily better
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Gate-set tomography on industrial and academic silicon two-qubit chips shows that coherence times shorten and gate and SPAM infidelities rise with temperature, with a sharp degradation above a crossover near 1 K. When these measured trends are inserted into a system-level power model that combines cryogenic cooling power with quantum-error-correction overhead, a finite optimal operating temperature appears that minimizes total power; colder operation is not always better.
What carries the argument
A general power model for silicon quantum computers that adds cryogenic cooling power to the extra power cost of quantum error correction. The model is driven by temperature-dependent two-qubit gate-set-tomography fidelities and coherence times measured on real industrial and academic chips, which exhibit a fidelity crossover near 1 K.
Load-bearing premise
The two-qubit gate and coherence trends measured on today’s small chips, together with the authors’ power model, correctly predict the thermal load and error-correction overhead of a full-scale fault-tolerant processor.
What would settle it
Build or simulate a larger multi-qubit silicon spin array, measure its two-qubit gate-set-tomography fidelity and total heat load versus temperature, and check whether the temperature that minimizes total power still sits near the ~1 K crossover predicted by the model.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript argues that silicon spin quantum computers possess a finite optimal operating temperature that minimizes total system power, defined as the sum of cryogenic cooling power and the power associated with quantum-error-correction (QEC) overhead. Using gate-set tomography (GST) on two-qubit devices fabricated in both industrial and academic processes, the authors report that elevated temperature shortens coherence and raises gate and SPAM infidelities, with a rapid degradation above a crossover near 1 K. These device-level trends are inserted into a general power model that balances cooling capacity against QEC overhead; the model is then used to locate an optimum and to extract design guidelines for large-scale, industry-compatible processors.
Significance. If the measured temperature dependence and the power model both survive scrutiny, the work would supply a concrete, system-level figure of merit linking device fidelity to cryogenic infrastructure cost—an issue of direct commercial relevance for silicon spin platforms. Explicit connection of GST-derived two-qubit error rates to a cooling-plus-QEC power budget, and the identification of a ~1 K crossover as the dominant design constraint, would be a useful contribution to the architecture literature. The use of both industrial and academic chips is a strength for generality claims.
major comments (3)
- The central claim—that a finite optimum exists for useful fault-tolerant processors—rests on extrapolating two-qubit GST fidelities, SPAM errors and T2 trends measured on small chips into a system-level power model. The abstract asserts this scaling step but does not indicate whether correlated errors, leakage, classical-control dissipation or interconnect heat, which appear only at large qubit counts, remain sub-dominant. Without that demonstration the optimum can shift or vanish; the manuscript must either bound these contributions or clearly limit the claim to the measured device class.
- The “general power model” is load-bearing: its functional forms for cooling power versus temperature and for QEC overhead versus physical error rate determine both the existence and the location of the reported optimum. The abstract gives no equations, free-parameter list, or sensitivity analysis. A major revision must supply the model equations, state which coefficients are measured versus assumed, and show how the optimum moves when those coefficients are varied over plausible ranges (including alternative cooling-power scalings and surface-code versus other QEC overheads).
- The claimed ~1 K crossover above which gate fidelity degrades rapidly is presented as the dominant influence on the optimum. Because only the abstract is available, it is impossible to verify whether the GST data actually exhibit a sharp crossover, whether the same scale appears in both industrial and academic devices, and whether the power-model optimum is robust when the crossover temperature is shifted by even a few hundred millikelvin. The full data (infidelity vs T, coherence vs T, with error bars) and a corresponding sensitivity plot are required.
minor comments (2)
- Abstract-only review: figure captions, raw GST process matrices, model equations and any comparison to independent cryogenic-power data are unavailable, so presentation quality cannot be assessed beyond the abstract wording.
- The abstract phrase “industry-compatible silicon spin quantum computing” should be sharpened: state which process node or foundry features are claimed to be industry-compatible so that the scope of the extrapolation is clear.
Circularity Check
No significant circularity: measured temperature-dependent fidelities feed a power model whose optimum is an output, not an input by construction.
full rationale
Only the abstract is available. It reports gate-set tomography on industrial and academic two-qubit silicon chips across temperatures, observes shortened coherence and rising gate/SPAM infidelities (with a rapid degradation above a ~1 K crossover), then builds a general power model that balances cryogenic cooling load against quantum-error-correction overhead and locates a finite optimal operating temperature. That chain is ordinary data-to-model inference: the measured fidelities and coherence are independent experimental inputs; the optimum is a derived minimum of the combined power function, not a quantity that was fitted or defined into existence. No self-definitional loop, no fitted parameter re-labeled as a prediction of itself, no load-bearing uniqueness theorem or ansatz imported solely via author self-citation, and no renaming of a known empirical pattern appears in the abstract. Extrapolation risk (whether small-chip GST trends and the power-model functional forms continue to dominate at fault-tolerant scale) is a correctness/assumption concern, not circularity. Score 0 is therefore the warranted finding.
Axiom & Free-Parameter Ledger
free parameters (2)
- power-model cooling and QEC scaling coefficients
- crossover temperature scale (~1 K)
axioms (3)
- domain assumption Raising operating temperature reduces cryogenic cooling power demand while increasing gate/SPAM error rates and thus QEC overhead.
- domain assumption Two-qubit GST fidelity and coherence trends on the measured chips are representative enough to inform large-scale fault-tolerant power budgets.
- domain assumption Gate set tomography provides a reliable estimate of gate and SPAM infidelities across the temperature range studied.
read the original abstract
Silicon spin qubits are a leading candidate for large-scale quantum computing owing to their compatibility with semiconductor manufacturing. However, scaling to useful fault-tolerant processors will likely generate thermal loads that exceed the cooling power available at millikelvin temperatures. Raising the operating temperature eases cooling requirements but reduces gate fidelity, increasing the overhead of quantum error correction. Identifying the operating temperature that minimizes total power consumption is therefore a key challenge for commercially viable quantum computers. Here, we use gate set tomography to benchmark two-qubit silicon chips fabricated in both industrial and academic environments over a range of temperatures. Elevated temperatures substantially shorten coherence times and increase gate and state-preparation-and-measurement infidelities. Based on these measurements, we develop a general power model for silicon quantum computers that combines cryogenic cooling requirements with error-correction overheads. We show that a finite optimal operating temperature exists and is strongly influenced by a crossover temperature near 1 K in current devices, above which gate fidelity degrades rapidly. These results connect device-level fidelity limitations to system-level power requirements, providing design guidelines for large-scale silicon quantum computers.
discussion (0)
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