prism-q 0.14.3

PRISM-Q: Performance Rust Interoperable Simulator for Quantum
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106

//! Shared helpers for the cross-backend correctness tests.
//!
//! Each per-backend test file declares `mod common;` and imports the
//! helpers it needs. Tolerance constants are split by backend so the
//! same helper can be reused with the right precision.

#![allow(dead_code)]

use prism_q::backend::statevector::StatevectorBackend;
use prism_q::backend::Backend;
use prism_q::circuit::{Circuit, Instruction};
use prism_q::sim;

pub const SV_EPS: f64 = 1e-10;
pub const STAB_EPS: f64 = 1e-12;
pub const SPARSE_EPS: f64 = 1e-10;
pub const MPS_EPS: f64 = 1e-9;
pub const TN_EPS: f64 = 1e-10;
pub const PRODUCT_EPS: f64 = 1e-12;
pub const FACTORED_EPS: f64 = 1e-10;

pub const SEED: u64 = 42;

pub fn sv_reference_probs(circuit: &Circuit) -> Vec<f64> {
    let mut backend = StatevectorBackend::new(SEED);
    sim::run_on(&mut backend, circuit).unwrap();
    backend.probabilities().unwrap()
}

pub fn assert_probs_close(actual: &[f64], expected: &[f64], eps: f64, label: &str) {
    assert_eq!(
        actual.len(),
        expected.len(),
        "{label}: probability vector length mismatch ({} vs {})",
        actual.len(),
        expected.len()
    );
    for (i, (a, e)) in actual.iter().zip(expected).enumerate() {
        let diff = (a - e).abs();
        assert!(
            diff < eps,
            "{label} prob[{i}]: expected {e:.12}, got {a:.12} (diff {diff:.2e}, eps {eps:.0e})"
        );
    }
}

pub fn assert_backend_matches_sv<B: Backend>(
    backend: &mut B,
    circuit: &Circuit,
    eps: f64,
    label: &str,
) {
    sim::run_on(backend, circuit).unwrap();
    let actual = backend.probabilities().unwrap();
    let expected = sv_reference_probs(circuit);
    assert_probs_close(&actual, &expected, eps, label);
}

pub fn run_unfused_probs<B: Backend>(backend: &mut B, circuit: &Circuit) -> Vec<f64> {
    backend
        .init(circuit.num_qubits, circuit.num_classical_bits)
        .unwrap();
    let expanded = if backend.supports_qft_block() {
        std::borrow::Cow::Borrowed(circuit)
    } else {
        prism_q::circuit::expand_qft_blocks(circuit)
    };
    for instr in &expanded.instructions {
        backend.apply(instr).unwrap();
    }
    backend.probabilities().unwrap()
}

pub fn run_fused_probs<B: Backend>(backend: &mut B, circuit: &Circuit) -> Vec<f64> {
    sim::run_on(backend, circuit).unwrap();
    backend.probabilities().unwrap()
}

pub fn assert_fused_matches_unfused<B: Backend, F: Fn() -> B>(
    new_backend: F,
    circuit: &Circuit,
    eps: f64,
    label: &str,
) {
    let mut unfused_backend = new_backend();
    let unfused = run_unfused_probs(&mut unfused_backend, circuit);
    let mut fused_backend = new_backend();
    let fused = run_fused_probs(&mut fused_backend, circuit);
    assert_probs_close(&fused, &unfused, eps, label);
}

pub fn is_clifford(circuit: &Circuit) -> bool {
    for instr in &circuit.instructions {
        match instr {
            Instruction::Gate { gate, .. } | Instruction::Conditional { gate, .. } => {
                if !gate.is_clifford() {
                    return false;
                }
            }
            Instruction::Measure { .. }
            | Instruction::Reset { .. }
            | Instruction::Barrier { .. } => {}
        }
    }
    true
}