cqlib-core 0.1.0-beta.4

The high-performance core foundation for the CQLib quantum computing ecosystem.
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
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192

// This code is part of Cqlib.
//
// (C) Copyright China Telecom Quantum Group 2025-2026
//
// This code is licensed under the Apache License, Version 2.0. You may
// obtain a copy of this license in the LICENSE.txt file in the root directory
// of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
//
// Any modifications or derivative works of this code must retain this
// copyright notice, and modified files need to carry a notice indicating
// that they have been altered from the originals.

use super::*;
use crate::circuit::{Circuit, Instruction, Qubit, StandardGate};
use crate::compile::CompilerError;
use crate::device::{Device, EdgeProp, InstructionProp, LogicalQubit, PhysicalQubit, Topology};
use std::collections::HashSet;

#[test]
fn greedy_layout_prioritizes_highest_weight_interaction() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let device = Device::line_from_qubits("line", vec![p0, p1, p2]).unwrap();
    let objective = LayoutObjective::topology_only();

    let mut circuit = Circuit::new(3);
    circuit.cx(Qubit::new(0), Qubit::new(2)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();

    let result = greedy_layout(&circuit, &device, &objective).unwrap();

    assert_eq!(result.layout.get_physical(LogicalQubit::new(0)), Some(p0));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(1)), Some(p1));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(2)), Some(p2));
    assert!(!result.diagnostics.is_perfect);
    assert_eq!(result.score.unwrap().distance, 5.0);
}

#[test]
fn greedy_layout_extends_from_mapped_endpoint() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let p3 = PhysicalQubit::new(3);
    let device = Device::line_from_qubits("line", vec![p0, p1, p2, p3]).unwrap();
    let objective = LayoutObjective::topology_only();

    let mut circuit = Circuit::new(3);
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(1), Qubit::new(2)).unwrap();

    let result = greedy_layout(&circuit, &device, &objective).unwrap();

    assert_eq!(result.layout.get_physical(LogicalQubit::new(0)), Some(p0));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(1)), Some(p1));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(2)), Some(p2));
    assert_eq!(result.layout.num_vacant_physical(), 1);
    assert!(result.diagnostics.is_perfect);
}

#[test]
fn greedy_layout_maps_idle_logical_qubits_deterministically() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let p3 = PhysicalQubit::new(3);
    let device = Device::line_from_qubits("line", vec![p0, p1, p2, p3]).unwrap();
    let objective = LayoutObjective::topology_only();
    let circuit = Circuit::new(3);

    let result = greedy_layout(&circuit, &device, &objective).unwrap();

    assert_eq!(result.layout.get_physical(LogicalQubit::new(0)), Some(p0));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(1)), Some(p1));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(2)), Some(p2));
    assert_eq!(result.layout.num_vacant_physical(), 1);
    assert!(result.diagnostics.is_perfect);
}

#[test]
fn greedy_layout_prefers_connected_pair_before_disconnected_tie_break() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let p3 = PhysicalQubit::new(3);
    let topology = Topology::new(vec![p0, p1, p2, p3], vec![(p2, p3, "cx".to_string())]).unwrap();
    let device = Device::new("sparse", HashSet::from_iter([p0, p1, p2, p3]), topology).unwrap();
    let objective = LayoutObjective::topology_only();

    let mut circuit = Circuit::new(2);
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();

    let result = greedy_layout(&circuit, &device, &objective).unwrap();

    assert_eq!(result.layout.get_physical(LogicalQubit::new(0)), Some(p2));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(1)), Some(p3));
    assert!(result.diagnostics.is_perfect);
}

#[test]
fn greedy_layout_rejects_insufficient_physical_qubits() {
    let p0 = PhysicalQubit::new(0);
    let topology = Topology::new(vec![p0], vec![]).unwrap();
    let device = Device::new("one", HashSet::from_iter([p0]), topology).unwrap();
    let objective = LayoutObjective::topology_only();
    let circuit = Circuit::new(2);

    let error = greedy_layout(&circuit, &device, &objective).unwrap_err();

    assert!(
        matches!(error, CompilerError::InvalidInput(message) if message.contains("2 logical qubits") && message.contains("1 usable physical qubits"))
    );
}

#[test]
fn greedy_layout_reports_non_perfect_for_non_adjacent_interaction() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let device = Device::line_from_qubits("line", vec![p0, p1, p2]).unwrap();
    let objective = LayoutObjective::topology_only();

    let mut circuit = Circuit::new(3);
    circuit.cx(Qubit::new(0), Qubit::new(2)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();

    let result = greedy_layout(&circuit, &device, &objective).unwrap();

    assert!(!result.diagnostics.is_perfect);
    assert_eq!(result.score.unwrap().distance, 5.0);
}

#[test]
fn greedy_layout_uses_fidelity_objective_for_ties() {
    let p0 = PhysicalQubit::new(0);
    let p1 = PhysicalQubit::new(1);
    let p2 = PhysicalQubit::new(2);
    let topology = Topology::new(
        vec![p0, p1, p2],
        vec![(p0, p1, "cx".to_string()), (p1, p2, "cx".to_string())],
    )
    .unwrap();
    let mut device = Device::new("line", HashSet::from_iter([p0, p1, p2]), topology).unwrap();
    device
        .add_edge_properties(
            p0,
            p1,
            EdgeProp::new()
                .with_native_instruction(InstructionProp::new(
                    Instruction::Standard(StandardGate::CX),
                    0.09,
                ))
                .unwrap()
                .with_native_instruction(InstructionProp::new(
                    Instruction::Standard(StandardGate::CZ),
                    0.001,
                ))
                .unwrap(),
        )
        .unwrap();
    device
        .add_edge_properties(
            p1,
            p2,
            EdgeProp::new()
                .with_native_instruction(InstructionProp::new(
                    Instruction::Standard(StandardGate::CX),
                    0.01,
                ))
                .unwrap(),
        )
        .unwrap();
    let physical = PhysicalLayoutGraph::from_device(&device).unwrap();
    let objective = LayoutObjective::auto_from_physical(&physical);

    let mut circuit = Circuit::new(2);
    circuit.cx(Qubit::new(0), Qubit::new(1)).unwrap();
    let analysis = analyze_circuit_for_layout(&circuit).unwrap();

    let result = greedy_layout_prepared(&analysis, &physical, &objective).unwrap();

    assert_eq!(result.layout.get_physical(LogicalQubit::new(0)), Some(p1));
    assert_eq!(result.layout.get_physical(LogicalQubit::new(1)), Some(p2));
    assert!(result.diagnostics.used_fidelity);
    assert_eq!(result.score.unwrap().two_qubit_error, 0.01);
}