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Fix order of noise application Pauli propagation #161

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Merged
david-pl merged 3 commits into from
Jun 26, 2026
Merged

Fix order of noise application Pauli propagation #161

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d5d9472
Add a test for definite heisenberg ordering of gates
david-pl Jun 25, 2026
9c88bc3
Fix the order (noise before gate) in a bunch of examples
david-pl Jun 25, 2026
38367f6
Fix all remaining places
david-pl Jun 25, 2026
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10 changes: 5 additions & 5 deletions crates/ppvm-pauli-sum/benches/trotter-scaling.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,22 +22,22 @@ fn trotter_func<T: Config<Coeff = f64, Strategy = CoefficientThreshold>>(
for _ in 0..steps {
// perform trotter step

// truncate after each gate application to be consistent with PP.jl
// truncate after each operation to be consistent with PP.jl
for i in 0..n {
state.rx(i, theta_x);
state.pauli_error(i, noise_params);
state.truncate();

state.pauli_error(i, noise_params);
state.rx(i, theta_x);
state.truncate();
}
for i in 0..n - 1 {
state.rzz(i, i + 1, theta_zz);
state.pauli_error(i + 1, noise_params);
state.truncate();

state.pauli_error(i, noise_params);
state.truncate();

state.pauli_error(i + 1, noise_params);
state.rzz(i, i + 1, theta_zz);
state.truncate();
}
}
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10 changes: 5 additions & 5 deletions crates/ppvm-pauli-sum/benches/trotter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,22 +24,22 @@ fn trotter_func<
for _ in 0..steps {
// perform trotter step

// truncate after each gate application to be consistent with PP.jl
// truncate after each operation to be consistent with PP.jl
for i in 0..n {
state.rx(i, theta_x);
state.pauli_error(i, noise_params);
state.truncate();

state.pauli_error(i, noise_params);
state.rx(i, theta_x);
state.truncate();
}
for i in 0..n - 1 {
state.rzz(i, i + 1, theta_zz);
state.pauli_error(i + 1, noise_params);
state.truncate();

state.pauli_error(i, noise_params);
state.truncate();

state.pauli_error(i + 1, noise_params);
state.rzz(i, i + 1, theta_zz);
state.truncate();
}
}
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8 changes: 4 additions & 4 deletions crates/ppvm-pauli-sum/examples/hash_quality.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,17 +47,17 @@ where
let theta_x = DT * H;
for _ in 0..steps {
for i in 0..n {
state.rx(i, theta_x);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.rx(i, theta_x);
state.truncate();
}
for i in 0..n - 1 {
state.rzz(i, i + 1, theta_zz);
state.pauli_error(i + 1, NOISE);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.pauli_error(i + 1, NOISE);
state.rzz(i, i + 1, theta_zz);
state.truncate();
}
}
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8 changes: 4 additions & 4 deletions crates/ppvm-pauli-sum/examples/trotter_qubit_sweep.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,17 +131,17 @@ where
let t0 = Instant::now();
for _ in 0..p.steps {
for i in 0..n {
state.rx(i, p.theta_x);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.rx(i, p.theta_x);
state.truncate();
}
for i in 0..n - 1 {
state.rzz(i, i + 1, p.theta_zz);
state.pauli_error(i + 1, NOISE);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.pauli_error(i + 1, NOISE);
state.rzz(i, i + 1, p.theta_zz);
state.truncate();
}
}
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8 changes: 4 additions & 4 deletions crates/ppvm-pauli-sum/examples/trotter_storage_cliff.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -73,17 +73,17 @@ macro_rules! run_tier {
let t0 = Instant::now();
for _ in 0..steps {
for i in 0..n {
state.rx(i, theta_x);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.rx(i, theta_x);
state.truncate();
}
for i in 0..n - 1 {
state.rzz(i, i + 1, theta_zz);
state.pauli_error(i + 1, NOISE);
state.truncate();
state.pauli_error(i, NOISE);
state.truncate();
state.pauli_error(i + 1, NOISE);
state.rzz(i, i + 1, theta_zz);
state.truncate();
}
}
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19 changes: 10 additions & 9 deletions crates/ppvm-pauli-sum/tests/trotter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,9 @@
//!
//! The benchmark itself only times `trotter_func` — it never reads the
//! propagated observable back, so nothing there guards the *result*. These
//! tests run the same gate sequence (`rx` + `rzz` + `pauli_error`, truncating
//! after every gate as the bench does) on a small chain and check:
//! tests run the same noisy gate sequence as the bench (physical gate then
//! noise, propagated as noise then gate in Heisenberg order, truncating after
//! every operation) on a small chain and check:
//!
//! 1. **Math regression** — the exact (untruncated, `NoStrategy`) expectation
//! value matches a frozen golden constant.
Expand Down Expand Up @@ -35,17 +36,17 @@ macro_rules! trotter_evolve {
($state:expr) => {{
for _ in 0..STEPS {
for i in 0..N {
$state.rx(i, THETA_X);
$state.truncate();
$state.pauli_error(i, NOISE);
$state.truncate();
$state.rx(i, THETA_X);
$state.truncate();
}
for i in 0..N - 1 {
$state.rzz(i, i + 1, THETA_ZZ);
$state.pauli_error(i + 1, NOISE);
$state.truncate();
$state.pauli_error(i, NOISE);
$state.truncate();
$state.pauli_error(i + 1, NOISE);
$state.rzz(i, i + 1, THETA_ZZ);
$state.truncate();
}
}
Expand Down Expand Up @@ -97,10 +98,10 @@ fn trotter_result_is_stable_and_truncation_is_faithful() {
let approx_val = expect_on_zero!(approx);

// (1) Math-regression guard: frozen golden for the exact circuit. Any
// change to the gate math (a wrong sign, bit-flip, or addressing bug in
// rx/rzz/pauli_error) moves this by O(1e-3) or more; the bound is far
// change to the gate math (a wrong sign, bit-flip, addressing bug, or
// gate/noise ordering mistake) moves this by O(1e-3) or more; the bound is far
// tighter than that yet far looser than cross-platform trig last-bit noise.
const GOLDEN: f64 = 2.161056303575631;
const GOLDEN: f64 = 2.1610566562692544;
assert!(
(exact_val - GOLDEN).abs() < 1e-9,
"exact Trotter expectation {exact_val} drifted from golden {GOLDEN}"
Expand Down
10 changes: 5 additions & 5 deletions docs/notebooks/trotter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -148,15 +148,15 @@ def trotter_step(state, n, theta_x, theta_zz):

def noisy_trotter_step(state, n, theta_x, theta_zz):
for i in range(n):
state.rx(i, theta=theta_x)
state.pauli_error(i, p=noise_1q)
state.loss_channel(i, p_loss)
state.pauli_error(i, p=noise_1q)
state.rx(i, theta=theta_x)

for i in range(n - 1):
state.rzz(i, i + 1, theta=theta_zz)
state.two_qubit_pauli_error(i, i + 1, p=noise_2q)
state.loss_channel(i, p_loss)
state.loss_channel(i + 1, p_loss)
state.loss_channel(i, p_loss)
state.two_qubit_pauli_error(i, i + 1, p=noise_2q)
state.rzz(i, i + 1, theta=theta_zz)


# %% [markdown]
Expand Down
6 changes: 3 additions & 3 deletions examples/trotter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,13 +70,13 @@ fn trotter(

// perform trotter step
for i in 0..n {
state.rx(i, theta_x);
state.pauli_error(i, noise_params);
state.rx(i, theta_x);
}
for i in 0..n - 1 {
state.rzz(i, i + 1, theta_zz);
state.pauli_error(i, noise_params);
state.pauli_error(i + 1, noise_params);
state.pauli_error(i, noise_params);
state.rzz(i, i + 1, theta_zz);
}

// truncate state in each iteration
Expand Down
6 changes: 3 additions & 3 deletions ppvm-python/test/benchmarks/test_trotter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -46,12 +46,12 @@ def trotter(state):
# application, to stay consistent with the Rust benchmark / PP.jl.
for _ in range(steps):
for i in range(N_QUBITS):
state.rx(i, theta=theta_x)
state.pauli_error(i, p=NOISE)
state.rx(i, theta=theta_x)
for i in range(N_QUBITS - 1):
state.rzz(i, i + 1, theta=theta_zz)
state.pauli_error(i, p=NOISE)
state.pauli_error(i + 1, p=NOISE)
state.pauli_error(i, p=NOISE)
state.rzz(i, i + 1, theta=theta_zz)


@pytest.mark.benchmark(group="trotter")
Expand Down
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