quantrs2_device/qec/
implementations.rs

1//! Quantum Error Correction Code Implementations
2//!
3//! This module provides implementations of various quantum error correction codes:
4//! - **Steane Code**: [[7,1,3]] CSS code that can correct any single qubit error
5//! - **Shor Code**: [[9,1,3]] code that protects against both bit and phase flips
6//! - **Surface Code**: Topological code with planar lattice geometry
7//! - **Toric Code**: Topological code defined on a toroidal lattice
8
9use quantrs2_core::qubit::QubitId;
10use scirs2_core::ndarray::Array1;
11use scirs2_core::Complex64;
12
13use super::{
14    LogicalOperator, LogicalOperatorType, PauliOperator, QECResult, QuantumErrorCode,
15    StabilizerGroup, StabilizerType,
16};
17
18/// Steane \[\[7,1,3\]\] quantum error correction code
19///
20/// The Steane code is a CSS (Calderbank-Shor-Steane) code that encodes
21/// one logical qubit into seven physical qubits and can correct any single
22/// qubit error (X, Y, or Z).
23pub struct SteaneCode;
24
25impl SteaneCode {
26    pub const fn new() -> Self {
27        Self
28    }
29}
30
31impl Default for SteaneCode {
32    fn default() -> Self {
33        Self::new()
34    }
35}
36
37impl QuantumErrorCode for SteaneCode {
38    fn get_stabilizers(&self) -> Vec<StabilizerGroup> {
39        vec![
40            // X-stabilizers for Steane [[7,1,3]] code
41            StabilizerGroup {
42                operators: vec![
43                    PauliOperator::X,
44                    PauliOperator::X,
45                    PauliOperator::X,
46                    PauliOperator::X,
47                    PauliOperator::I,
48                    PauliOperator::I,
49                    PauliOperator::I,
50                ],
51                qubits: vec![
52                    QubitId::new(0),
53                    QubitId::new(1),
54                    QubitId::new(2),
55                    QubitId::new(3),
56                    QubitId::new(4),
57                    QubitId::new(5),
58                    QubitId::new(6),
59                ],
60                stabilizer_type: StabilizerType::XStabilizer,
61                weight: 4,
62            },
63            StabilizerGroup {
64                operators: vec![
65                    PauliOperator::I,
66                    PauliOperator::X,
67                    PauliOperator::X,
68                    PauliOperator::I,
69                    PauliOperator::X,
70                    PauliOperator::X,
71                    PauliOperator::I,
72                ],
73                qubits: vec![
74                    QubitId::new(0),
75                    QubitId::new(1),
76                    QubitId::new(2),
77                    QubitId::new(3),
78                    QubitId::new(4),
79                    QubitId::new(5),
80                    QubitId::new(6),
81                ],
82                stabilizer_type: StabilizerType::XStabilizer,
83                weight: 4,
84            },
85            StabilizerGroup {
86                operators: vec![
87                    PauliOperator::I,
88                    PauliOperator::I,
89                    PauliOperator::I,
90                    PauliOperator::X,
91                    PauliOperator::X,
92                    PauliOperator::X,
93                    PauliOperator::X,
94                ],
95                qubits: vec![
96                    QubitId::new(0),
97                    QubitId::new(1),
98                    QubitId::new(2),
99                    QubitId::new(3),
100                    QubitId::new(4),
101                    QubitId::new(5),
102                    QubitId::new(6),
103                ],
104                stabilizer_type: StabilizerType::XStabilizer,
105                weight: 4,
106            },
107            // Z-stabilizers for Steane [[7,1,3]] code
108            StabilizerGroup {
109                operators: vec![
110                    PauliOperator::Z,
111                    PauliOperator::Z,
112                    PauliOperator::Z,
113                    PauliOperator::Z,
114                    PauliOperator::I,
115                    PauliOperator::I,
116                    PauliOperator::I,
117                ],
118                qubits: vec![
119                    QubitId::new(0),
120                    QubitId::new(1),
121                    QubitId::new(2),
122                    QubitId::new(3),
123                    QubitId::new(4),
124                    QubitId::new(5),
125                    QubitId::new(6),
126                ],
127                stabilizer_type: StabilizerType::ZStabilizer,
128                weight: 4,
129            },
130            StabilizerGroup {
131                operators: vec![
132                    PauliOperator::I,
133                    PauliOperator::Z,
134                    PauliOperator::Z,
135                    PauliOperator::I,
136                    PauliOperator::Z,
137                    PauliOperator::Z,
138                    PauliOperator::I,
139                ],
140                qubits: vec![
141                    QubitId::new(0),
142                    QubitId::new(1),
143                    QubitId::new(2),
144                    QubitId::new(3),
145                    QubitId::new(4),
146                    QubitId::new(5),
147                    QubitId::new(6),
148                ],
149                stabilizer_type: StabilizerType::ZStabilizer,
150                weight: 4,
151            },
152            StabilizerGroup {
153                operators: vec![
154                    PauliOperator::I,
155                    PauliOperator::I,
156                    PauliOperator::I,
157                    PauliOperator::Z,
158                    PauliOperator::Z,
159                    PauliOperator::Z,
160                    PauliOperator::Z,
161                ],
162                qubits: vec![
163                    QubitId::new(0),
164                    QubitId::new(1),
165                    QubitId::new(2),
166                    QubitId::new(3),
167                    QubitId::new(4),
168                    QubitId::new(5),
169                    QubitId::new(6),
170                ],
171                stabilizer_type: StabilizerType::ZStabilizer,
172                weight: 4,
173            },
174        ]
175    }
176
177    fn get_logical_operators(&self) -> Vec<LogicalOperator> {
178        vec![
179            // Logical X operator (acts on all 7 qubits)
180            LogicalOperator {
181                operators: vec![
182                    PauliOperator::X,
183                    PauliOperator::X,
184                    PauliOperator::X,
185                    PauliOperator::X,
186                    PauliOperator::X,
187                    PauliOperator::X,
188                    PauliOperator::X,
189                ],
190                operator_type: LogicalOperatorType::LogicalX,
191            },
192            // Logical Z operator (acts on all 7 qubits)
193            LogicalOperator {
194                operators: vec![
195                    PauliOperator::Z,
196                    PauliOperator::Z,
197                    PauliOperator::Z,
198                    PauliOperator::Z,
199                    PauliOperator::Z,
200                    PauliOperator::Z,
201                    PauliOperator::Z,
202                ],
203                operator_type: LogicalOperatorType::LogicalZ,
204            },
205        ]
206    }
207
208    fn distance(&self) -> usize {
209        3
210    }
211
212    fn num_data_qubits(&self) -> usize {
213        7
214    }
215
216    fn num_ancilla_qubits(&self) -> usize {
217        6
218    }
219
220    fn logical_qubit_count(&self) -> usize {
221        1
222    }
223
224    fn encode_logical_state(
225        &self,
226        logical_state: &Array1<Complex64>,
227    ) -> QECResult<Array1<Complex64>> {
228        Ok(logical_state.clone())
229    }
230}
231
232/// Shor \[\[9,1,3\]\] quantum error correction code
233///
234/// The Shor code protects one logical qubit using nine physical qubits
235/// and can correct any single qubit error. It combines both bit-flip
236/// and phase-flip protection.
237pub struct ShorCode;
238
239impl ShorCode {
240    pub const fn new() -> Self {
241        Self
242    }
243}
244
245impl Default for ShorCode {
246    fn default() -> Self {
247        Self::new()
248    }
249}
250
251impl QuantumErrorCode for ShorCode {
252    fn get_stabilizers(&self) -> Vec<StabilizerGroup> {
253        vec![
254            // Z-stabilizers for bit-flip correction (6 generators)
255            StabilizerGroup {
256                operators: vec![
257                    PauliOperator::Z,
258                    PauliOperator::Z,
259                    PauliOperator::I,
260                    PauliOperator::I,
261                    PauliOperator::I,
262                    PauliOperator::I,
263                    PauliOperator::I,
264                    PauliOperator::I,
265                    PauliOperator::I,
266                ],
267                qubits: vec![
268                    QubitId::new(0),
269                    QubitId::new(1),
270                    QubitId::new(2),
271                    QubitId::new(3),
272                    QubitId::new(4),
273                    QubitId::new(5),
274                    QubitId::new(6),
275                    QubitId::new(7),
276                    QubitId::new(8),
277                ],
278                stabilizer_type: StabilizerType::ZStabilizer,
279                weight: 2,
280            },
281            StabilizerGroup {
282                operators: vec![
283                    PauliOperator::I,
284                    PauliOperator::Z,
285                    PauliOperator::Z,
286                    PauliOperator::I,
287                    PauliOperator::I,
288                    PauliOperator::I,
289                    PauliOperator::I,
290                    PauliOperator::I,
291                    PauliOperator::I,
292                ],
293                qubits: vec![
294                    QubitId::new(0),
295                    QubitId::new(1),
296                    QubitId::new(2),
297                    QubitId::new(3),
298                    QubitId::new(4),
299                    QubitId::new(5),
300                    QubitId::new(6),
301                    QubitId::new(7),
302                    QubitId::new(8),
303                ],
304                stabilizer_type: StabilizerType::ZStabilizer,
305                weight: 2,
306            },
307            StabilizerGroup {
308                operators: vec![
309                    PauliOperator::I,
310                    PauliOperator::I,
311                    PauliOperator::I,
312                    PauliOperator::Z,
313                    PauliOperator::Z,
314                    PauliOperator::I,
315                    PauliOperator::I,
316                    PauliOperator::I,
317                    PauliOperator::I,
318                ],
319                qubits: vec![
320                    QubitId::new(0),
321                    QubitId::new(1),
322                    QubitId::new(2),
323                    QubitId::new(3),
324                    QubitId::new(4),
325                    QubitId::new(5),
326                    QubitId::new(6),
327                    QubitId::new(7),
328                    QubitId::new(8),
329                ],
330                stabilizer_type: StabilizerType::ZStabilizer,
331                weight: 2,
332            },
333            StabilizerGroup {
334                operators: vec![
335                    PauliOperator::I,
336                    PauliOperator::I,
337                    PauliOperator::I,
338                    PauliOperator::I,
339                    PauliOperator::Z,
340                    PauliOperator::Z,
341                    PauliOperator::I,
342                    PauliOperator::I,
343                    PauliOperator::I,
344                ],
345                qubits: vec![
346                    QubitId::new(0),
347                    QubitId::new(1),
348                    QubitId::new(2),
349                    QubitId::new(3),
350                    QubitId::new(4),
351                    QubitId::new(5),
352                    QubitId::new(6),
353                    QubitId::new(7),
354                    QubitId::new(8),
355                ],
356                stabilizer_type: StabilizerType::ZStabilizer,
357                weight: 2,
358            },
359            StabilizerGroup {
360                operators: vec![
361                    PauliOperator::I,
362                    PauliOperator::I,
363                    PauliOperator::I,
364                    PauliOperator::I,
365                    PauliOperator::I,
366                    PauliOperator::I,
367                    PauliOperator::Z,
368                    PauliOperator::Z,
369                    PauliOperator::I,
370                ],
371                qubits: vec![
372                    QubitId::new(0),
373                    QubitId::new(1),
374                    QubitId::new(2),
375                    QubitId::new(3),
376                    QubitId::new(4),
377                    QubitId::new(5),
378                    QubitId::new(6),
379                    QubitId::new(7),
380                    QubitId::new(8),
381                ],
382                stabilizer_type: StabilizerType::ZStabilizer,
383                weight: 2,
384            },
385            StabilizerGroup {
386                operators: vec![
387                    PauliOperator::I,
388                    PauliOperator::I,
389                    PauliOperator::I,
390                    PauliOperator::I,
391                    PauliOperator::I,
392                    PauliOperator::I,
393                    PauliOperator::I,
394                    PauliOperator::Z,
395                    PauliOperator::Z,
396                ],
397                qubits: vec![
398                    QubitId::new(0),
399                    QubitId::new(1),
400                    QubitId::new(2),
401                    QubitId::new(3),
402                    QubitId::new(4),
403                    QubitId::new(5),
404                    QubitId::new(6),
405                    QubitId::new(7),
406                    QubitId::new(8),
407                ],
408                stabilizer_type: StabilizerType::ZStabilizer,
409                weight: 2,
410            },
411            // X-stabilizers for phase-flip correction (2 generators)
412            StabilizerGroup {
413                operators: vec![
414                    PauliOperator::X,
415                    PauliOperator::X,
416                    PauliOperator::X,
417                    PauliOperator::X,
418                    PauliOperator::X,
419                    PauliOperator::X,
420                    PauliOperator::I,
421                    PauliOperator::I,
422                    PauliOperator::I,
423                ],
424                qubits: vec![
425                    QubitId::new(0),
426                    QubitId::new(1),
427                    QubitId::new(2),
428                    QubitId::new(3),
429                    QubitId::new(4),
430                    QubitId::new(5),
431                    QubitId::new(6),
432                    QubitId::new(7),
433                    QubitId::new(8),
434                ],
435                stabilizer_type: StabilizerType::XStabilizer,
436                weight: 6,
437            },
438            StabilizerGroup {
439                operators: vec![
440                    PauliOperator::I,
441                    PauliOperator::I,
442                    PauliOperator::I,
443                    PauliOperator::X,
444                    PauliOperator::X,
445                    PauliOperator::X,
446                    PauliOperator::X,
447                    PauliOperator::X,
448                    PauliOperator::X,
449                ],
450                qubits: vec![
451                    QubitId::new(0),
452                    QubitId::new(1),
453                    QubitId::new(2),
454                    QubitId::new(3),
455                    QubitId::new(4),
456                    QubitId::new(5),
457                    QubitId::new(6),
458                    QubitId::new(7),
459                    QubitId::new(8),
460                ],
461                stabilizer_type: StabilizerType::XStabilizer,
462                weight: 6,
463            },
464        ]
465    }
466
467    fn get_logical_operators(&self) -> Vec<LogicalOperator> {
468        vec![
469            // Logical X operator (one qubit from each group)
470            LogicalOperator {
471                operators: vec![
472                    PauliOperator::X,
473                    PauliOperator::I,
474                    PauliOperator::I,
475                    PauliOperator::X,
476                    PauliOperator::I,
477                    PauliOperator::I,
478                    PauliOperator::X,
479                    PauliOperator::I,
480                    PauliOperator::I,
481                ],
482                operator_type: LogicalOperatorType::LogicalX,
483            },
484            // Logical Z operator (all qubits)
485            LogicalOperator {
486                operators: vec![
487                    PauliOperator::Z,
488                    PauliOperator::Z,
489                    PauliOperator::Z,
490                    PauliOperator::Z,
491                    PauliOperator::Z,
492                    PauliOperator::Z,
493                    PauliOperator::Z,
494                    PauliOperator::Z,
495                    PauliOperator::Z,
496                ],
497                operator_type: LogicalOperatorType::LogicalZ,
498            },
499        ]
500    }
501
502    fn distance(&self) -> usize {
503        3
504    }
505
506    fn num_data_qubits(&self) -> usize {
507        9
508    }
509
510    fn num_ancilla_qubits(&self) -> usize {
511        8
512    }
513
514    fn logical_qubit_count(&self) -> usize {
515        1
516    }
517
518    fn encode_logical_state(
519        &self,
520        logical_state: &Array1<Complex64>,
521    ) -> QECResult<Array1<Complex64>> {
522        Ok(logical_state.clone())
523    }
524}
525
526/// Surface code with parameterized distance
527///
528/// The surface code is a topological quantum error correction code
529/// defined on a 2D planar lattice. The code distance determines the
530/// number of errors that can be corrected.
531pub struct SurfaceCode {
532    distance: usize,
533}
534
535impl SurfaceCode {
536    pub const fn new(distance: usize) -> Self {
537        Self { distance }
538    }
539}
540
541impl QuantumErrorCode for SurfaceCode {
542    fn get_stabilizers(&self) -> Vec<StabilizerGroup> {
543        // For simplicity, implement stabilizers for distance-3 surface code
544        // This is a basic implementation - full surface codes require more complex lattice handling
545        if self.distance != 3 {
546            // Return a minimal set for other distances - could be extended
547            return vec![
548                StabilizerGroup {
549                    operators: vec![PauliOperator::X, PauliOperator::X],
550                    qubits: vec![QubitId::new(0), QubitId::new(1)],
551                    stabilizer_type: StabilizerType::XStabilizer,
552                    weight: 2,
553                },
554                StabilizerGroup {
555                    operators: vec![PauliOperator::Z, PauliOperator::Z],
556                    qubits: vec![QubitId::new(0), QubitId::new(1)],
557                    stabilizer_type: StabilizerType::ZStabilizer,
558                    weight: 2,
559                },
560            ];
561        }
562
563        // Distance-3 surface code stabilizers (simplified square lattice)
564        // Data qubits: 0-8 arranged as:
565        // 0 1 2
566        // 3 4 5
567        // 6 7 8
568        vec![
569            // X-stabilizers (vertex type)
570            StabilizerGroup {
571                operators: vec![
572                    PauliOperator::X,
573                    PauliOperator::X,
574                    PauliOperator::I,
575                    PauliOperator::X,
576                    PauliOperator::X,
577                    PauliOperator::I,
578                    PauliOperator::I,
579                    PauliOperator::I,
580                    PauliOperator::I,
581                ],
582                qubits: vec![
583                    QubitId::new(0),
584                    QubitId::new(1),
585                    QubitId::new(2),
586                    QubitId::new(3),
587                    QubitId::new(4),
588                    QubitId::new(5),
589                    QubitId::new(6),
590                    QubitId::new(7),
591                    QubitId::new(8),
592                ],
593                stabilizer_type: StabilizerType::XStabilizer,
594                weight: 4,
595            },
596            StabilizerGroup {
597                operators: vec![
598                    PauliOperator::I,
599                    PauliOperator::X,
600                    PauliOperator::X,
601                    PauliOperator::I,
602                    PauliOperator::X,
603                    PauliOperator::X,
604                    PauliOperator::I,
605                    PauliOperator::I,
606                    PauliOperator::I,
607                ],
608                qubits: vec![
609                    QubitId::new(0),
610                    QubitId::new(1),
611                    QubitId::new(2),
612                    QubitId::new(3),
613                    QubitId::new(4),
614                    QubitId::new(5),
615                    QubitId::new(6),
616                    QubitId::new(7),
617                    QubitId::new(8),
618                ],
619                stabilizer_type: StabilizerType::XStabilizer,
620                weight: 4,
621            },
622            StabilizerGroup {
623                operators: vec![
624                    PauliOperator::I,
625                    PauliOperator::I,
626                    PauliOperator::I,
627                    PauliOperator::X,
628                    PauliOperator::X,
629                    PauliOperator::I,
630                    PauliOperator::X,
631                    PauliOperator::X,
632                    PauliOperator::I,
633                ],
634                qubits: vec![
635                    QubitId::new(0),
636                    QubitId::new(1),
637                    QubitId::new(2),
638                    QubitId::new(3),
639                    QubitId::new(4),
640                    QubitId::new(5),
641                    QubitId::new(6),
642                    QubitId::new(7),
643                    QubitId::new(8),
644                ],
645                stabilizer_type: StabilizerType::XStabilizer,
646                weight: 4,
647            },
648            StabilizerGroup {
649                operators: vec![
650                    PauliOperator::I,
651                    PauliOperator::I,
652                    PauliOperator::I,
653                    PauliOperator::I,
654                    PauliOperator::X,
655                    PauliOperator::X,
656                    PauliOperator::I,
657                    PauliOperator::X,
658                    PauliOperator::X,
659                ],
660                qubits: vec![
661                    QubitId::new(0),
662                    QubitId::new(1),
663                    QubitId::new(2),
664                    QubitId::new(3),
665                    QubitId::new(4),
666                    QubitId::new(5),
667                    QubitId::new(6),
668                    QubitId::new(7),
669                    QubitId::new(8),
670                ],
671                stabilizer_type: StabilizerType::XStabilizer,
672                weight: 4,
673            },
674            // Z-stabilizers (plaquette type)
675            StabilizerGroup {
676                operators: vec![
677                    PauliOperator::Z,
678                    PauliOperator::Z,
679                    PauliOperator::I,
680                    PauliOperator::Z,
681                    PauliOperator::Z,
682                    PauliOperator::I,
683                    PauliOperator::I,
684                    PauliOperator::I,
685                    PauliOperator::I,
686                ],
687                qubits: vec![
688                    QubitId::new(0),
689                    QubitId::new(1),
690                    QubitId::new(2),
691                    QubitId::new(3),
692                    QubitId::new(4),
693                    QubitId::new(5),
694                    QubitId::new(6),
695                    QubitId::new(7),
696                    QubitId::new(8),
697                ],
698                stabilizer_type: StabilizerType::ZStabilizer,
699                weight: 4,
700            },
701            StabilizerGroup {
702                operators: vec![
703                    PauliOperator::I,
704                    PauliOperator::Z,
705                    PauliOperator::Z,
706                    PauliOperator::I,
707                    PauliOperator::Z,
708                    PauliOperator::Z,
709                    PauliOperator::I,
710                    PauliOperator::I,
711                    PauliOperator::I,
712                ],
713                qubits: vec![
714                    QubitId::new(0),
715                    QubitId::new(1),
716                    QubitId::new(2),
717                    QubitId::new(3),
718                    QubitId::new(4),
719                    QubitId::new(5),
720                    QubitId::new(6),
721                    QubitId::new(7),
722                    QubitId::new(8),
723                ],
724                stabilizer_type: StabilizerType::ZStabilizer,
725                weight: 4,
726            },
727            StabilizerGroup {
728                operators: vec![
729                    PauliOperator::I,
730                    PauliOperator::I,
731                    PauliOperator::I,
732                    PauliOperator::Z,
733                    PauliOperator::Z,
734                    PauliOperator::I,
735                    PauliOperator::Z,
736                    PauliOperator::Z,
737                    PauliOperator::I,
738                ],
739                qubits: vec![
740                    QubitId::new(0),
741                    QubitId::new(1),
742                    QubitId::new(2),
743                    QubitId::new(3),
744                    QubitId::new(4),
745                    QubitId::new(5),
746                    QubitId::new(6),
747                    QubitId::new(7),
748                    QubitId::new(8),
749                ],
750                stabilizer_type: StabilizerType::ZStabilizer,
751                weight: 4,
752            },
753            StabilizerGroup {
754                operators: vec![
755                    PauliOperator::I,
756                    PauliOperator::I,
757                    PauliOperator::I,
758                    PauliOperator::I,
759                    PauliOperator::Z,
760                    PauliOperator::Z,
761                    PauliOperator::I,
762                    PauliOperator::Z,
763                    PauliOperator::Z,
764                ],
765                qubits: vec![
766                    QubitId::new(0),
767                    QubitId::new(1),
768                    QubitId::new(2),
769                    QubitId::new(3),
770                    QubitId::new(4),
771                    QubitId::new(5),
772                    QubitId::new(6),
773                    QubitId::new(7),
774                    QubitId::new(8),
775                ],
776                stabilizer_type: StabilizerType::ZStabilizer,
777                weight: 4,
778            },
779        ]
780    }
781
782    fn get_logical_operators(&self) -> Vec<LogicalOperator> {
783        if self.distance != 3 {
784            // Basic logical operators for other distances
785            return vec![
786                LogicalOperator {
787                    operators: vec![PauliOperator::X, PauliOperator::I],
788                    operator_type: LogicalOperatorType::LogicalX,
789                },
790                LogicalOperator {
791                    operators: vec![PauliOperator::Z, PauliOperator::I],
792                    operator_type: LogicalOperatorType::LogicalZ,
793                },
794            ];
795        }
796
797        // Distance-3 surface code logical operators
798        vec![
799            // Logical X operator (horizontal string)
800            LogicalOperator {
801                operators: vec![
802                    PauliOperator::X,
803                    PauliOperator::I,
804                    PauliOperator::X,
805                    PauliOperator::I,
806                    PauliOperator::I,
807                    PauliOperator::I,
808                    PauliOperator::X,
809                    PauliOperator::I,
810                    PauliOperator::X,
811                ],
812                operator_type: LogicalOperatorType::LogicalX,
813            },
814            // Logical Z operator (vertical string)
815            LogicalOperator {
816                operators: vec![
817                    PauliOperator::Z,
818                    PauliOperator::Z,
819                    PauliOperator::Z,
820                    PauliOperator::I,
821                    PauliOperator::I,
822                    PauliOperator::I,
823                    PauliOperator::I,
824                    PauliOperator::I,
825                    PauliOperator::I,
826                ],
827                operator_type: LogicalOperatorType::LogicalZ,
828            },
829        ]
830    }
831
832    fn distance(&self) -> usize {
833        self.distance
834    }
835
836    fn num_data_qubits(&self) -> usize {
837        self.distance * self.distance
838    }
839
840    fn num_ancilla_qubits(&self) -> usize {
841        self.distance * self.distance - 1
842    }
843
844    fn logical_qubit_count(&self) -> usize {
845        1
846    }
847
848    fn encode_logical_state(
849        &self,
850        logical_state: &Array1<Complex64>,
851    ) -> QECResult<Array1<Complex64>> {
852        Ok(logical_state.clone())
853    }
854}
855
856/// Toric code with parameterized lattice dimensions
857///
858/// The toric code is a topological quantum error correction code
859/// defined on a torus (periodic boundary conditions in both directions).
860/// It encodes two logical qubits.
861pub struct ToricCode {
862    dimensions: (usize, usize),
863}
864
865impl ToricCode {
866    pub const fn new(dimensions: (usize, usize)) -> Self {
867        Self { dimensions }
868    }
869}
870
871impl QuantumErrorCode for ToricCode {
872    fn get_stabilizers(&self) -> Vec<StabilizerGroup> {
873        // Implement a basic 2x2 toric code for simplicity
874        // For general dimensions, this would need more complex lattice handling
875        if self.dimensions != (2, 2) {
876            // Return minimal stabilizers for other dimensions
877            return vec![
878                StabilizerGroup {
879                    operators: vec![PauliOperator::X, PauliOperator::X],
880                    qubits: vec![QubitId::new(0), QubitId::new(1)],
881                    stabilizer_type: StabilizerType::XStabilizer,
882                    weight: 2,
883                },
884                StabilizerGroup {
885                    operators: vec![PauliOperator::Z, PauliOperator::Z],
886                    qubits: vec![QubitId::new(0), QubitId::new(1)],
887                    stabilizer_type: StabilizerType::ZStabilizer,
888                    weight: 2,
889                },
890            ];
891        }
892
893        // 2x2 toric code has 8 data qubits arranged on a torus
894        // X-stabilizers (vertex type) and Z-stabilizers (plaquette type)
895        vec![
896            // X-stabilizers (vertex type) - 4 stabilizers for 2x2 torus
897            StabilizerGroup {
898                operators: vec![
899                    PauliOperator::X,
900                    PauliOperator::X,
901                    PauliOperator::I,
902                    PauliOperator::I,
903                    PauliOperator::X,
904                    PauliOperator::X,
905                    PauliOperator::I,
906                    PauliOperator::I,
907                ],
908                qubits: vec![
909                    QubitId::new(0),
910                    QubitId::new(1),
911                    QubitId::new(2),
912                    QubitId::new(3),
913                    QubitId::new(4),
914                    QubitId::new(5),
915                    QubitId::new(6),
916                    QubitId::new(7),
917                ],
918                stabilizer_type: StabilizerType::XStabilizer,
919                weight: 4,
920            },
921            StabilizerGroup {
922                operators: vec![
923                    PauliOperator::I,
924                    PauliOperator::I,
925                    PauliOperator::X,
926                    PauliOperator::X,
927                    PauliOperator::I,
928                    PauliOperator::I,
929                    PauliOperator::X,
930                    PauliOperator::X,
931                ],
932                qubits: vec![
933                    QubitId::new(0),
934                    QubitId::new(1),
935                    QubitId::new(2),
936                    QubitId::new(3),
937                    QubitId::new(4),
938                    QubitId::new(5),
939                    QubitId::new(6),
940                    QubitId::new(7),
941                ],
942                stabilizer_type: StabilizerType::XStabilizer,
943                weight: 4,
944            },
945            StabilizerGroup {
946                operators: vec![
947                    PauliOperator::I,
948                    PauliOperator::I,
949                    PauliOperator::I,
950                    PauliOperator::I,
951                    PauliOperator::X,
952                    PauliOperator::X,
953                    PauliOperator::I,
954                    PauliOperator::I,
955                ],
956                qubits: vec![
957                    QubitId::new(0),
958                    QubitId::new(1),
959                    QubitId::new(2),
960                    QubitId::new(3),
961                    QubitId::new(4),
962                    QubitId::new(5),
963                    QubitId::new(6),
964                    QubitId::new(7),
965                ],
966                stabilizer_type: StabilizerType::XStabilizer,
967                weight: 4,
968            },
969            StabilizerGroup {
970                operators: vec![
971                    PauliOperator::I,
972                    PauliOperator::I,
973                    PauliOperator::I,
974                    PauliOperator::I,
975                    PauliOperator::I,
976                    PauliOperator::I,
977                    PauliOperator::X,
978                    PauliOperator::X,
979                ],
980                qubits: vec![
981                    QubitId::new(0),
982                    QubitId::new(1),
983                    QubitId::new(2),
984                    QubitId::new(3),
985                    QubitId::new(4),
986                    QubitId::new(5),
987                    QubitId::new(6),
988                    QubitId::new(7),
989                ],
990                stabilizer_type: StabilizerType::XStabilizer,
991                weight: 4,
992            },
993            // Z-stabilizers (plaquette type) - 4 stabilizers for 2x2 torus
994            StabilizerGroup {
995                operators: vec![
996                    PauliOperator::Z,
997                    PauliOperator::Z,
998                    PauliOperator::I,
999                    PauliOperator::I,
1000                    PauliOperator::Z,
1001                    PauliOperator::Z,
1002                    PauliOperator::I,
1003                    PauliOperator::I,
1004                ],
1005                qubits: vec![
1006                    QubitId::new(0),
1007                    QubitId::new(1),
1008                    QubitId::new(2),
1009                    QubitId::new(3),
1010                    QubitId::new(4),
1011                    QubitId::new(5),
1012                    QubitId::new(6),
1013                    QubitId::new(7),
1014                ],
1015                stabilizer_type: StabilizerType::ZStabilizer,
1016                weight: 4,
1017            },
1018            StabilizerGroup {
1019                operators: vec![
1020                    PauliOperator::I,
1021                    PauliOperator::I,
1022                    PauliOperator::Z,
1023                    PauliOperator::Z,
1024                    PauliOperator::I,
1025                    PauliOperator::I,
1026                    PauliOperator::Z,
1027                    PauliOperator::Z,
1028                ],
1029                qubits: vec![
1030                    QubitId::new(0),
1031                    QubitId::new(1),
1032                    QubitId::new(2),
1033                    QubitId::new(3),
1034                    QubitId::new(4),
1035                    QubitId::new(5),
1036                    QubitId::new(6),
1037                    QubitId::new(7),
1038                ],
1039                stabilizer_type: StabilizerType::ZStabilizer,
1040                weight: 4,
1041            },
1042            StabilizerGroup {
1043                operators: vec![
1044                    PauliOperator::I,
1045                    PauliOperator::I,
1046                    PauliOperator::I,
1047                    PauliOperator::I,
1048                    PauliOperator::Z,
1049                    PauliOperator::Z,
1050                    PauliOperator::I,
1051                    PauliOperator::I,
1052                ],
1053                qubits: vec![
1054                    QubitId::new(0),
1055                    QubitId::new(1),
1056                    QubitId::new(2),
1057                    QubitId::new(3),
1058                    QubitId::new(4),
1059                    QubitId::new(5),
1060                    QubitId::new(6),
1061                    QubitId::new(7),
1062                ],
1063                stabilizer_type: StabilizerType::ZStabilizer,
1064                weight: 4,
1065            },
1066            StabilizerGroup {
1067                operators: vec![
1068                    PauliOperator::I,
1069                    PauliOperator::I,
1070                    PauliOperator::I,
1071                    PauliOperator::I,
1072                    PauliOperator::I,
1073                    PauliOperator::I,
1074                    PauliOperator::Z,
1075                    PauliOperator::Z,
1076                ],
1077                qubits: vec![
1078                    QubitId::new(0),
1079                    QubitId::new(1),
1080                    QubitId::new(2),
1081                    QubitId::new(3),
1082                    QubitId::new(4),
1083                    QubitId::new(5),
1084                    QubitId::new(6),
1085                    QubitId::new(7),
1086                ],
1087                stabilizer_type: StabilizerType::ZStabilizer,
1088                weight: 4,
1089            },
1090        ]
1091    }
1092
1093    fn get_logical_operators(&self) -> Vec<LogicalOperator> {
1094        if self.dimensions != (2, 2) {
1095            // Basic logical operators for other dimensions
1096            return vec![
1097                LogicalOperator {
1098                    operators: vec![PauliOperator::X, PauliOperator::I],
1099                    operator_type: LogicalOperatorType::LogicalX,
1100                },
1101                LogicalOperator {
1102                    operators: vec![PauliOperator::Z, PauliOperator::I],
1103                    operator_type: LogicalOperatorType::LogicalZ,
1104                },
1105            ];
1106        }
1107
1108        // 2x2 toric code logical operators (2 logical qubits due to torus topology)
1109        vec![
1110            // First logical X operator (horizontal winding)
1111            LogicalOperator {
1112                operators: vec![
1113                    PauliOperator::X,
1114                    PauliOperator::I,
1115                    PauliOperator::X,
1116                    PauliOperator::I,
1117                    PauliOperator::I,
1118                    PauliOperator::I,
1119                    PauliOperator::I,
1120                    PauliOperator::I,
1121                ],
1122                operator_type: LogicalOperatorType::LogicalX,
1123            },
1124            // First logical Z operator (vertical winding)
1125            LogicalOperator {
1126                operators: vec![
1127                    PauliOperator::Z,
1128                    PauliOperator::I,
1129                    PauliOperator::I,
1130                    PauliOperator::I,
1131                    PauliOperator::Z,
1132                    PauliOperator::I,
1133                    PauliOperator::I,
1134                    PauliOperator::I,
1135                ],
1136                operator_type: LogicalOperatorType::LogicalZ,
1137            },
1138        ]
1139    }
1140
1141    fn distance(&self) -> usize {
1142        self.dimensions.0.min(self.dimensions.1)
1143    }
1144
1145    fn num_data_qubits(&self) -> usize {
1146        2 * self.dimensions.0 * self.dimensions.1
1147    }
1148
1149    fn num_ancilla_qubits(&self) -> usize {
1150        self.dimensions.0 * self.dimensions.1
1151    }
1152
1153    fn logical_qubit_count(&self) -> usize {
1154        2
1155    }
1156
1157    fn encode_logical_state(
1158        &self,
1159        logical_state: &Array1<Complex64>,
1160    ) -> QECResult<Array1<Complex64>> {
1161        Ok(logical_state.clone())
1162    }
1163}
quantrs2_device/qec/implementations.rs

quantrs2_device/qec/
implementations.rs
