/
inner_product.py
78 lines (58 loc) · 2.61 KB
/
inner_product.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
# This code is part of Qiskit.
#
# (C) Copyright IBM 2020.
#
# 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.
"""InnerProduct circuit."""
from qiskit.circuit import QuantumRegister, QuantumCircuit
class InnerProduct(QuantumCircuit):
r"""A 2n-qubit Boolean function that computes the inner product of
two n-qubit vectors over :math:`F_2`.
This implementation is a phase oracle which computes the following transform.
.. math::
\mathcal{IP}_{2n} : F_2^{2n} \rightarrow {-1, 1}
\mathcal{IP}_{2n}(x_1, \cdots, x_n, y_1, \cdots, y_n) = (-1)^{x.y}
The corresponding unitary is a diagonal, which induces a -1 phase on any inputs
where the inner product of the top and bottom registers is 1. Otherwise it keeps
the input intact.
.. parsed-literal::
q0_0: ─■──────────
│
q0_1: ─┼──■───────
│ │
q0_2: ─┼──┼──■────
│ │ │
q0_3: ─┼──┼──┼──■─
│ │ │ │
q1_0: ─■──┼──┼──┼─
│ │ │
q1_1: ────■──┼──┼─
│ │
q1_2: ───────■──┼─
│
q1_3: ──────────■─
Reference Circuit:
.. plot::
from qiskit.circuit.library import InnerProduct
from qiskit.visualization.library import _generate_circuit_library_visualization
circuit = InnerProduct(4)
_generate_circuit_library_visualization(circuit)
"""
def __init__(self, num_qubits: int) -> None:
"""Return a circuit to compute the inner product of 2 n-qubit registers.
Args:
num_qubits: width of top and bottom registers (half total circuit width)
"""
qr_a = QuantumRegister(num_qubits)
qr_b = QuantumRegister(num_qubits)
inner = QuantumCircuit(qr_a, qr_b, name="inner_product")
for i in range(num_qubits):
inner.cz(qr_a[i], qr_b[i])
super().__init__(*inner.qregs, name="inner_product")
self.compose(inner.to_gate(), qubits=self.qubits, inplace=True)