f04751f608
useless_format (a literal, its braces unescaped), manual_range_contains, some_filter (`then_some` on two pure accessors), sliced_string_as_bytes (the cut is at a character boundary), map_or_identity, manual_contains, chunks_exact_to_as_chunks (the same chunks, the remainder dropped as before), borrow_deref_ref, needless_borrows_for_generic_args (the closure is Copy), ptr_arg, useless_vec, single_match, unusual_byte_groupings (the same value), assertions_on_constants (now checked at compile time). Allowed with their reasons: should_implement_trait on Amp::add and Amp::mul, which callers name; redundant_comparisons in a test that asserts both energy floors; large_enum_variant on the Metal state vector's passes; needless_return in the SME member off aarch64, where the `return` ends the function. Co-Authored-By: Claude Opus 5.5 <[email protected]>
89 lines
4.5 KiB
Rust
89 lines
4.5 KiB
Rust
//! Patched cross-entropy benchmarking from a circuit, its patches and the
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//! measured shots: each patch simulated exactly on the dense state vector.
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//!
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//! ```text
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//! cargo run --release --example patch_xeb --features quantum_sv -- CIRCUIT.qasm SHOTS.u64 PATCHES
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//! ```
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//!
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//! `CIRCUIT.qasm`: OpenQASM 3 with `rz`, `rx`, `ry`, `h`, `x`, `sx`, `cz`,
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//! `cx` (barriers and measurements are skipped). Its two-qubit gates must stay
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//! inside the patches: a patched circuit has its boundary couplers removed.
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//! `SHOTS.u64`: one little-endian `u64` a shot, qubit q at bit q.
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//! `PATCHES`: the patches' qubits, `0,1,2;3,4,5`.
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//!
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//! Prints, per patch: its qubits, the mean of `2^n·p(x)` over the shots, its
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//! ideal value `2^n·Σp² − 1` (the XEB of the patch's own exact samples), and
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//! the normalised fidelity `(2^n·mean p − 1) / (2^n·Σp² − 1)`; then the
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//! product of the fidelities and its standard error (the patches' errors
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//! added in quadrature, relative).
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use wai_quantum::gates::Gate;
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use wai_quantum::quantum_sv::StateVector;
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fn main() {
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let args: Vec<String> = std::env::args().collect();
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let src = std::fs::read_to_string(&args[1]).expect("the circuit reads");
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let raw = std::fs::read(&args[2]).expect("the shots read");
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let shots: Vec<u64> = raw.as_chunks::<8>().0.iter().map(|b| u64::from_le_bytes(*b)).collect();
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let patches: Vec<Vec<u32>> = args[3].split(';').map(|p| p.split(',').map(|q| q.trim().parse().unwrap()).collect()).collect();
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// The gates, with their qubits.
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let mut gates: Vec<(String, f64, Vec<u32>)> = Vec::new();
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for line in src.lines().map(str::trim) {
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let line = line.trim_end_matches(';');
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if line.is_empty() || ["OPENQASM", "include", "bit", "qubit", "barrier", "c["].iter().any(|p| line.starts_with(p)) || line.contains("measure") {
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continue;
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}
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let (head, args) = line.split_once(' ').expect("a gate and its qubits");
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let (name, theta) = match head.split_once('(') {
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Some((n, p)) => (n.to_string(), p.trim_end_matches(')').parse::<f64>().expect("one angle")),
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None => (head.to_string(), 0.0),
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};
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let qs: Vec<u32> = args.split(',').map(|a| a.trim().trim_start_matches("q[").trim_end_matches(']').parse().unwrap()).collect();
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gates.push((name, theta, qs));
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}
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let mut product = 1.0;
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let mut rel_var = 0.0;
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for patch in &patches {
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let n = patch.len() as u32;
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let local = |q: u32| patch.iter().position(|&p| p == q).map(|i| i as u32);
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let mut sv = StateVector::zero(n).unwrap();
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for (name, theta, qs) in &gates {
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let l: Vec<Option<u32>> = qs.iter().map(|&q| local(q)).collect();
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if l.iter().all(Option::is_none) {
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continue;
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}
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let l: Vec<u32> = l.into_iter().map(|x| x.expect("a gate crossing the patch boundary")).collect();
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let g = match (name.as_str(), l.as_slice()) {
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("rz", [a]) => Gate::rz(*a, *theta),
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("rx", [a]) => Gate::rx(*a, *theta),
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("ry", [a]) => Gate::ry(*a, *theta),
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("h", [a]) => Gate::h(*a),
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("x", [a]) => Gate::x(*a),
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("sx", [a]) => Gate::sqrt_x(*a),
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("cz", [a, b]) => Gate::cz(*a, *b),
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("cx", [a, b]) => Gate::cx(*a, *b),
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_ => panic!("gate {name} on {qs:?}"),
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};
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sv.apply(&g).unwrap();
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}
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let dim = (n as f64).exp2();
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let prob = |i: usize| sv.re[i] * sv.re[i] + sv.im[i] * sv.im[i];
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let ideal = dim * (0..sv.re.len()).map(|i| prob(i) * prob(i)).sum::<f64>() - 1.0;
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// Each shot's patch bits, as the state vector's index (local qubit 0 most significant).
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let vals: Vec<f64> = shots
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.iter()
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.map(|&x| {
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let idx = patch.iter().enumerate().fold(0usize, |i, (l, &q)| i | (((x >> q) & 1) as usize) << (n as usize - 1 - l));
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dim * prob(idx)
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})
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.collect();
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let mean = vals.iter().sum::<f64>() / vals.len() as f64;
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let var = vals.iter().map(|v| (v - mean).powi(2)).sum::<f64>() / (vals.len() as f64 - 1.0);
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let f = (mean - 1.0) / ideal;
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let se = (var / vals.len() as f64).sqrt() / ideal;
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product *= f;
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rel_var += (se / f).powi(2);
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println!("patch {n} qubits: mean 2^n·p {mean:.6}, ideal xeb {ideal:.6}, fidelity {f:.6} ± {se:.6}");
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}
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println!("fidelity {product:.6e} ± {:.6e} ({} shots)", product.abs() * rel_var.sqrt(), shots.len());
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}
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