wai-quantum

A deterministic quantum stack in pure Rust. Byte-exact circuit simulation, the operational layer around it, and signed energy-accounted receipts binding every stage.

No QPU, no cloud service, no vendor SDK, and no system libraries — so the same source runs natively, in the browser via wasm, and as a WASI component at the edge, producing byte-identical results and receipts on all three.

[dependencies]
wai-quantum = "0.3"

use wai_quantum::quantum::Circuit;
use wai_quantum::quantum_toolchain as qt;

let mut c = Circuit::new(3);
c.h(0).cx(0, 1).cx(1, 2);              // GHZ
let sv = c.simulate().unwrap();
println!("{:?}", qt::top_outcomes(&sv, 2));   // |000> 0.5, |111> 0.5
// a portable identity for the reconstruction — same on every machine
let h: [u8; 32] = sv.statevector_hash();

What's in it

Cross-architecture reproducibility is tested, not asserted. The full test suite passes under wasm32-wasip2 on wasmtime as well as natively, and the floating-point results — entropy, the Holevo bound — are pinned to their exact IEEE-754 bits, so a platform that computes something different fails the suite instead of quietly returning a different number:

CARGO_TARGET_WASM32_WASIP2_RUNNER=wasmtime cargo test --release --target wasm32-wasip2 --features full

The same binary answers what a state carries, not only what a circuit does:

wai-quantum entropy bell --keep 0    # half a Bell pair: 1 bit, invisible to a state vector
wai-quantum channel depolarizing --prob 0.5
wai-quantum bb84 --eavesdrop         # interception shows up in the error rate
wai-quantum chsh                     # 2 sqrt(2), exactly, not sampled
wai-quantum qutrit                   # d = 3, not just qubits

channel prints the Holevo bound before and after, and it can only fall: noise never creates information.

| quantum | byte-exact statevector simulation (dyadic Clifford+T+P(k)) | | quantum_toolchain | algorithm library, backend recommendation, OpenQASM 2/3 ingest of what the mainstream toolchains actually export — both register and both measurement spellings, rx/ry/rz/sx/u/u2/u3/crz, and exact rational-multiple-of-pi angles (non-dyadic angles are refused, never rounded) — Bloch / entanglement / purity analysis | | quantum_stabilizer | stabilizer (CHP) tableau — O(n²), scales far past statevector | | quantum_mps | tensor-network (matrix-product-state) backend | | quantum_pauli | sparse-Pauli / Heisenberg observable propagation over the dyadic gate set (up to 64 qubits) | | quantum_spd | sparse Pauli dynamics at utility scale: arbitrary-angle Pauli rotations on up to 1024 qubits, exact Clifford and quarter-turn rotations, a rigorous bound on what truncation can move a result, and the 127-qubit heavy-hex kicked-Ising circuits — whose exactly computed 5-step magnetization it reproduces on all 127 qubits | | quantum_spd_receipt | a signed, energy-accounted receipt over a sparse-Pauli-dynamics run, re-checkable bit for bit on any machine | | quantum_bptn | tensor-network states on the hardware graph: simple-update evolution with belief-propagation environments and re-gauging, the device's couplings applied a layer at a time in parallel (bit-identical to one at a time). Exact on trees; on the 127-qubit lattice it gives the exactly computed 5-step magnetization to 4e-7 at bond dimension 32 — an independent check on sparse Pauli dynamics, whose errors it does not share | | quantum_resource | fault-tolerant resource estimation: from a program's logical counts (qubits, T, Toffoli and rotation gates, measurements) to code distance, T-state factories found by exhaustive search, physical qubits and runtime, on six reference qubits and three codes, with the qubits-versus-time frontier. Reproduces the published worked examples to their printed precision | | quantum_resource_receipt | a signed, energy-accounted receipt over an estimate, re-checkable bit for bit on any machine | | quantum_receipt | signed, energy-accounted receipt over a reconstruction | | quantum_ops | the operations/attestation layer | | quantum_cal, quantum_control, quantum_noise | calibration, filter-function robust control, DD noise spectroscopy, Cycle-Benchmarking noise learning | | quantum_mitigate | zero-noise extrapolation, readout M3, classical shadows | | quantum_qec | CSS codes (distance verified by exhaustive search, not asserted) — rotated surface [[d²,1,d]], toric, bivariate-bicycle, and the [[7,1,3]] colour code, whose self-duality buys a transversal logical Hadamard — one round, no ancillas, no surgery — verified on the simulator, with the surface code shown failing the same move — with two decoders: union-find (weighted matching, single-shot, space-time with faulty measurement, and circuit-level with hook errors; imports and exports Stim-syntax detector error models, so other tools' noise models decode here and ours decode there) and Relay-BP (for qLDPC) | | quantum_compile | Clifford routing + stabilizer-tableau equivalence proof | | quantum_atom | neutral-atom register preparation (Hungarian / LSAP) | | quantum_qir | QIR export + ingest — emit and parse QIR (the QIR Alliance's LLVM-based IR); emitted modules validated with llvm-as, and 9 of 10 catalog algorithms re-ingest to a bit-identical statevector | | quantum_comm | key distribution and security: BB84 with an intercept-resend eavesdropper (a quiet channel gives a perfect key; interception costs a quarter of it), and the no-cloning theorem priced | | quantum_qudit | qubits and qutrits: the Weyl–Heisenberg group, the Fourier gate over Z_d, the controlled sum — exact for d = 2 and 3 | | quantum_info | mixed states: density matrices, the partial trace, purity, exact Pauli expectations, and CHSH against the classical and Tsirelson bounds | | quantum_source | the limits on encoding and transport: von Neumann entropy, the Schumacher limit, and the Holevo bound — which says n qubits carry at most n classical bits, so quantum does not compress classical media | | quantum_channel | transport itself: Kraus channels (bit flip, dephasing, depolarizing, amplitude damping), and linear-inversion tomography to see what actually arrived — with the law that a channel can only lose information, never create it | | quantum_qbom | Quantum Bill of Materials — stage receipts into one manifest | | quantum_vml, quantum_phasor, quantum_qfhrr, quantum_kernel, quantum_qdata, quantum_phasor_meter | the interference / phasor ML layer | | full | everything |

Default features are quantum, quantum_toolchain, quantum_receipt.

Speed

Byte-exactness is the contract, so the simulator is optimised only in ways that cannot move a single amplitude: identity does nothing, a diagonal gate phases half the state with one multiply rather than four, and X — so CX — is a swap with no arithmetic at all. fxmul(ONE, x) == x exactly in this fixed point, which is what makes those paths provably identical rather than merely close, and they are checked against the previous implementation amplitude by amplitude.

An all-real matrix — H, and any real rotation — halves its multiplies too, since the imaginary cross terms are multiplications by exactly zero.

At 20 qubits that is 8.9x on Z, 7.1x on X, 4.6x on CZ, 4.3x on CX, 3.4x on T, 1.9x on Y and 1.8x on H.

Utility scale

quantum_spd evolves an observable instead of a state, so a circuit costs what its non-Clifford rotations make it cost rather than 2ⁿ:

cargo run --release --example utility --features quantum_spd -- 0.2 20 1e-4

computes ⟨Z₆₂⟩ after 20 Trotter steps of the 127-qubit heavy-hex kicked-Ising circuit in a fraction of a second, with the bound on how far truncation can have moved it. --example utility_mz checks the 5-step magnetization against the exactly computed values for every angle, and tests/utility_reference.rs holds the published references. quantum_bptn computes the same circuits as tensor networks (--example utility_bptn), so a result can be checked by a second method that does not share the first one's approximation.

Fault-tolerant resources

What a program would need on a machine that does not exist yet is a resource estimate, and claims about that machine stand on one. quantum_resource makes the estimate a deterministic function of its inputs:

wai-quantum estimate factoring                        # 2048-bit factoring, six reference qubits
wai-quantum estimate chemistry --qubit ns-e4 --frontier
wai-quantum estimate factoring --qubit ns-e4 --receipt | wai-quantum verify

The model is the planar-ISA one of arXiv:2211.07629: surface and Floquet-code patches, lattice surgery, and 15-to-1 distillation factories chosen by exhaustive search over unit types, distances and copy counts. The tests reproduce that source's own tables:

• every code distance and factory of its per-qubit factoring table, down to the copy counts;
• the distance, factory count, physical qubits and runtime of all twelve factoring and chemistry rows of its summary table;
• all twelve factory counts of its dynamics rows. Factoring on the (ns, 10⁻⁴) qubit comes out at d = 13, 18 factories, 8,716,258 physical qubits and 17 h 43 min.

Holding the model to those tables exposed places where the source's prose and its numbers disagree, and one factory that is not the minimum of its own model. Each is documented in the module and settled by the tables.

A sealed estimate names its whole job (counts, qubit, code, budget, slowdown and search limits, to the bit). Re-running it anywhere must reproduce every figure, down to each factory round, and the bytes are the same natively and as a WASI component.

Determinism

Simulation is byte-exact: amplitudes are dyadic fixed-point, so a circuit reconstructs to the same statevector_hash on every machine and every target. The approximate methods (MPS truncation, sparse Pauli dynamics, the phasor/ML layer) are reproducible f64: IEEE-754-strict, and identical given the same inputs and seed on every platform. They are documented as such rather than claimed byte-exact. Their sin, cos, ln and atan2 are computed in-crate from + − × ÷, because platform math libraries differ in the last place — enough that four of these layers once gave different bits natively and as a WASI component. tests/bit_identity.rs pins one result from each, so any platform whose arithmetic differs fails there.

A receipt separates the two halves of a cost honestly: work is portable-exact (n_ops · 2^n amplitude updates, recomputed by the verifier, so a sink cannot inflate it) and energy is measured-attested (only the signer can vouch for its own silicon). Signatures travel between substrates because the computation is reproducible — not because two runtimes agreed to trust each other.

An energy figure is only comparable with another when it says how it was acquired — read from the silicon's own counter, from a calibrated instrument, from a model, or a constant. quantum_energy::Labelled seals that acquisition class, with its declared uncertainty, inside the receipt's signature, and LabelledQbom does the same per entry of a bill of materials. A receipt sealed without a label keeps exactly the bytes it always had. MaybeLabelled parses and verifies a receipt in whichever form it arrives, and checks a job's link to its calibration in either form. A label's declared uncertainty must be at least the 0.5/√3 µJ (≈ 0.289 µJ) that rounding the figure to whole microjoules adds: joules_micro × relative_ppm of at least 288 676.

Also available

• A CLI (wai-quantum in the wai crate) — run circuits, emit OpenQASM, seal and verify receipts, native or under wasmtime.
• A WASI-HTTP component serving the stack as an ordinary HTTP handler.
• Browser demos and a course: https://wai.transaction.science/quantum-ide

License

Apache-2.0