Before you spend QPU time — or a week of HPC — Atlas answers one question: does this circuit actually need a quantum computer, or can a laptop reproduce it? On a measured corpus the answer is "classical" far more often than the market assumes. Atlas shows it the only way worth trusting: measured, multi-method, and auditable — before you spend, not a guess after. It separates signal from noise on that one decision; it does not add PQC, key-breaking, or any "quantum advantage" claim.
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Quantum hardware is scarce and expensive, and so is the HPC time it takes to simulate a circuit classically. The expensive mistake is running the wrong one: paying for a QPU on a circuit your laptop could have settled in seconds, or sinking a cluster into a circuit that was never going to be classically tractable. Today most teams decide this by intuition or rule-of-thumb. Atlas turns that decision into a measured, repeatable, auditable verdict — the same way a compiler decides CPU vs. GPU, but for the classical-vs-quantum frontier.
The quantum market is saturated with two narratives: hype ("everything needs a QPU") and threat ("quantum will break everything"). Atlas does neither. It is a sober instrument that separates signal from noise on one decision — classical-tractable or not — and refuses to over-claim on either side.
| Atlas does | Atlas does NOT |
|---|---|
| Measure the cheapest classical method that handles your circuit, and exhibit it | Claim "quantum advantage" — that needs a lower bound over every classical algorithm (BQP≠BPP, open) |
| Say "don't buy the QPU" with a constructive, checkable witness | Touch post-quantum cryptography, key-breaking, or any "quantum threat" story |
| Abstain (MEDIUM) when the evidence honestly splits | Promise it can prove you need a QPU — the strongest honest statement is "out of measured classical reach → verify" |
Independent estimators agree the circuit is classically simulable. When the case is cheap and certified, Atlas can hand you the result — not just the verdict.
No cheap classical route survives the checks. Atlas tells you so before you spend the QPU time, and shows you which estimator drew the line and why.
And a third, honest answer: MEDIUM — "I can't certify either side." That is not a failure. Deciding exactly whether a circuit is classically simulable is provably super-exponential (Leone et al., arXiv:2602.22330), so a calibrated abstention is the only honest answer when the evidence splits. Atlas never feigns certainty.
OpenQASM or a Qiskit circuit. No account needed for the free hosted web.
Stim (#T / stabilizer), quimb (MPS bond), cotengra (treewidth), and Pauli-spread — each measuring the circuit from a different mathematical space.
A hash-stamped verdict with the per-estimator evidence ledger — re-derivable, archivable, citable.
The full reasoning — the four estimators, the agreement certificate, and the honesty principles — is on the Methodology page.
Stated honestly, not marketed. Atlas does not try to beat the specialized engines — and shouldn't. It answers a different question.
| Layer | vs. SoTA |
|---|---|
| Quantum simulation (statevector / MPS) | well below — quimb / Aer own this |
| Tensor-network contraction · stabilizer · compiler | below — cotengra / Stim / Qiskit own these |
| Route adjudication — which method should you run? | potentially ahead — almost no one builds this layer |
| Explainability · failure-mode awareness | at or above |
An independent deep review (primary sources) found all four papers Atlas cites to be real and accurately characterised, and judged the self-positioning vs. SoTA honest. The one reservation was verifiability — the calibration corpus and repo are not yet fully public — not veracity. Every result on the Evidence page is reproducible from the named scripts and data manifests without us handing over the corpus. The code is open; the measurements are the moat.