forked from quantumlib/Cirq
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathshors_code.py
128 lines (113 loc) · 5.91 KB
/
shors_code.py
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
# pylint: disable=wrong-or-nonexistent-copyright-notice
""" Shor's code is a stabilizer code for quantum error correction.
It uses 9 qubits to encode 1 logic qubit and is able to correct
at most one bit flip and one sign flip or their combination.
(0, 0): ───@───@───H───@───@───@───@───X───H───@───@───X───M───
│ │ │ │ │ │ │ │ │ │
(0, 1): ───┼───┼───────X───┼───X───┼───@───────┼───┼───┼───M───
│ │ │ │ │ │ │ │
(0, 2): ───┼───┼───────────X───────X───@───────┼───┼───┼───M───
│ │ │ │ │
(0, 3): ───X───┼───H───@───@───@───@───X───H───X───┼───@───M───
│ │ │ │ │ │ │ │
(0, 4): ───────┼───────X───┼───X───┼───@───────────┼───┼───M───
│ │ │ │ │ │
(0, 5): ───────┼───────────X───────X───@───────────┼───┼───M───
│ │ │
(0, 6): ───────X───H───@───@───@───@───X───H───────X───@───M───
│ │ │ │ │
(0, 7): ───────────────X───┼───X───┼───@───────────────────M───
│ │ │
(0, 8): ───────────────────X───────X───@───────────────────M───
reference: P. W. Shor, Phys. Rev. A, 52, R2493 (1995).
"""
import random
import cirq
class OneQubitShorsCode:
def __init__(self):
self.num_physical_qubits = 9
self.physical_qubits = cirq.LineQubit.range(self.num_physical_qubits)
def encode(self):
yield cirq.Moment([cirq.CNOT(self.physical_qubits[0], self.physical_qubits[3])])
yield cirq.Moment([cirq.CNOT(self.physical_qubits[0], self.physical_qubits[6])])
yield cirq.Moment(
[
cirq.H(self.physical_qubits[0]),
cirq.H(self.physical_qubits[3]),
cirq.H(self.physical_qubits[6]),
]
)
yield cirq.Moment(
[
cirq.CNOT(self.physical_qubits[0], self.physical_qubits[1]),
cirq.CNOT(self.physical_qubits[3], self.physical_qubits[4]),
cirq.CNOT(self.physical_qubits[6], self.physical_qubits[7]),
]
)
yield cirq.Moment(
[
cirq.CNOT(self.physical_qubits[0], self.physical_qubits[2]),
cirq.CNOT(self.physical_qubits[3], self.physical_qubits[5]),
cirq.CNOT(self.physical_qubits[6], self.physical_qubits[8]),
]
)
def apply_gate(self, gate: cirq.Gate, pos: int):
if pos > self.num_physical_qubits:
raise IndexError
else:
return gate(self.physical_qubits[pos])
def correct(self):
yield cirq.Moment(
[
cirq.CNOT(self.physical_qubits[0], self.physical_qubits[1]),
cirq.CNOT(self.physical_qubits[3], self.physical_qubits[4]),
cirq.CNOT(self.physical_qubits[6], self.physical_qubits[7]),
]
)
yield cirq.Moment(
[
cirq.CNOT(self.physical_qubits[0], self.physical_qubits[2]),
cirq.CNOT(self.physical_qubits[3], self.physical_qubits[5]),
cirq.CNOT(self.physical_qubits[6], self.physical_qubits[8]),
]
)
yield cirq.Moment(
[
cirq.CCNOT(
self.physical_qubits[1], self.physical_qubits[2], self.physical_qubits[0]
),
cirq.CCNOT(
self.physical_qubits[4], self.physical_qubits[5], self.physical_qubits[3]
),
cirq.CCNOT(
self.physical_qubits[7], self.physical_qubits[8], self.physical_qubits[6]
),
]
)
yield cirq.Moment(
[
cirq.H(self.physical_qubits[0]),
cirq.H(self.physical_qubits[3]),
cirq.H(self.physical_qubits[6]),
]
)
yield cirq.Moment([cirq.CNOT(self.physical_qubits[0], self.physical_qubits[3])])
yield cirq.Moment([cirq.CNOT(self.physical_qubits[0], self.physical_qubits[6])])
yield cirq.Moment(
[cirq.CCNOT(self.physical_qubits[3], self.physical_qubits[6], self.physical_qubits[0])]
)
if __name__ == '__main__': # pragma: no cover
# create circuit with 9 physical qubits
code = OneQubitShorsCode()
circuit = cirq.Circuit(code.apply_gate(cirq.X ** (1 / 4), 0))
print(cirq.dirac_notation(circuit.final_state_vector(initial_state=0)))
circuit += cirq.Circuit(code.encode())
print(cirq.dirac_notation(circuit.final_state_vector(initial_state=0)))
# create error
circuit += cirq.Circuit(
code.apply_gate(cirq.X, random.randint(0, code.num_physical_qubits - 1))
)
print(cirq.dirac_notation(circuit.final_state_vector(initial_state=0)))
# correct error and decode
circuit += cirq.Circuit(code.correct())
print(cirq.dirac_notation(circuit.final_state_vector(initial_state=0)))