# Source code for discopy.quantum.ansatze

```# -*- coding: utf-8 -*-

"""
Quantum circuit ansätze.

Summary
-------

.. autosummary::
:template: class.rst
:nosignatures:
:toctree:

IQPansatz
Sim14ansatz
Sim15ansatz

"""

from discopy.matrix import get_backend
from discopy.quantum.circuit import qubit, Circuit, Id

[docs]def IQPansatz(n_qubits, params) -> Circuit:
"""
Build an IQP ansatz on n qubits, if n = 1 returns an Euler decomposition.

>>> pprint = lambda c: print(str(c.foliation()).replace(' >>', '\\n  >>'))
>>> pprint(IQPansatz(3, [[0.1, 0.2], [0.3, 0.4]]))
H @ H @ H
>> CRz(0.1) @ qubit
>> H @ CRz(0.2)
>> qubit @ H @ H
>> CRz(0.3) @ qubit
>> qubit @ CRz(0.4)
>>> print(IQPansatz(1, [0.3, 0.8, 0.4]))
Rx(0.3) >> Rz(0.8) >> Rx(0.4)
"""
from discopy.quantum.gates import H, Rx, Rz, CRz

np = get_backend()

def layer(thetas):
rotations = Id(qubit ** n_qubits).then(*(
qubit ** i @ CRz(thetas[i]) @ qubit ** (n_qubits - 2 - i)
for i in range(n_qubits - 1)))
if n_qubits == 1:
circuit = Rx(params[0]) >> Rz(params[1]) >> Rx(params[2])
elif len(np.shape(params)) != 2\
or np.shape(params)[1] != n_qubits - 1:
raise ValueError(
f"Expected params of shape (depth, {n_qubits - 1})")
else:
depth = np.shape(params)[0]
circuit = Id(qubit ** n_qubits).then(*(
layer(params[i]) for i in range(depth)))
return circuit

[docs]def Sim14ansatz(n_qubits, params) -> Circuit:
"""
Builds a modified version of circuit 14 from arXiv:1905.10876

Replaces circuit-block construction with two rings of CRx gates, in
opposite orientation.

>>> pprint = lambda c: print(str(c.foliation()).replace(' >>', '\\n  >>'))
>>> pprint(Sim14ansatz(3, [[i/10 for i in range(12)]]))
Ry(0) @ Ry(0.1) @ Ry(0.2)
>> Controlled(Rx(0.3), distance=2)
>> Controlled(Rx(0.4), distance=-1) @ qubit
>> Ry(0.6) @ Controlled(Rx(0.5), distance=-1)
>> qubit @ Ry(0.7) @ Ry(0.8)
>> CRx(0.9) @ qubit
>> Controlled(Rx(1), distance=-2)
>> qubit @ CRx(1.1)
>>> print(Sim14ansatz(1, [0.1, 0.2, 0.3]))
Rx(0.1) >> Rz(0.2) >> Rx(0.3)
"""
from discopy.quantum.gates import Rx, Ry, Rz

np = get_backend()

def layer(thetas):
sublayer1 = Id().tensor(
*([Ry(theta) for theta in thetas[:n_qubits]]))

for i in range(n_qubits):
src = i
tgt = (i - 1) % n_qubits
sublayer1 = sublayer1.CRx(thetas[n_qubits + i], src, tgt)

sublayer2 = Id().tensor(
*([Ry(theta) for theta in thetas[2 * n_qubits: 3 * n_qubits]]))

for i in range(n_qubits, 0, -1):
src = i % n_qubits
tgt = (i + 1) % n_qubits
sublayer2 = sublayer2.CRx(thetas[-i], src, tgt)

return sublayer1 >> sublayer2

params_shape = np.shape(params)

if n_qubits == 1:
circuit = Rx(params[0]) >> Rz(params[1]) >> Rx(params[2])
elif (len(params_shape) != 2) or (params_shape[1] != 4 * n_qubits):
raise ValueError(
f"Expected params of shape (depth, {4 * n_qubits})")
else:
depth = params_shape[0]
circuit = Id(qubit ** n_qubits).then(*(
layer(params[i]) for i in range(depth)))

return circuit

[docs]def Sim15ansatz(n_qubits, params) -> Circuit:
"""
Builds a modified version of circuit 15 from arXiv:1905.10876

Replaces circuit-block construction with two rings of CNOT gates, in
opposite orientation.

>>> pprint = lambda c: print(str(c.foliation()).replace(' >>', '\\n  >>'))
>>> pprint(Sim15ansatz(3, [[0.1, 0.2, 0.3, 0.4, 0.5, 0.6]]))
Ry(0.1) @ Ry(0.2) @ Ry(0.3)
>> Controlled(X, distance=2)
>> Controlled(X, distance=-1) @ qubit
>> Ry(0.4) @ Controlled(X, distance=-1)
>> qubit @ Ry(0.5) @ Ry(0.6)
>> CX @ qubit
>> Controlled(X, distance=-2)
>> qubit @ CX
>>> print(Sim15ansatz(1, [0.1, 0.2, 0.3]))
Rx(0.1) >> Rz(0.2) >> Rx(0.3)
"""
from discopy.quantum.gates import Rx, Ry, Rz

np = get_backend()

def layer(thetas):
sublayer1 = Id().tensor(
*([Ry(theta) for theta in thetas[:n_qubits]]))

for i in range(n_qubits):
src = i
tgt = (i - 1) % n_qubits
sublayer1 = sublayer1.CX(src, tgt)

sublayer2 = Id().tensor(
*([Ry(theta) for theta in thetas[n_qubits:]]))

for i in range(n_qubits, 0, -1):
src = i % n_qubits
tgt = (i + 1) % n_qubits
sublayer2 = sublayer2.CX(src, tgt)

return sublayer1 >> sublayer2

params_shape = np.shape(params)

if n_qubits == 1:
circuit = Rx(params[0]) >> Rz(params[1]) >> Rx(params[2])
elif (len(params_shape) != 2) or (params_shape[1] != 2 * n_qubits):
raise ValueError(
f"Expected params of shape (depth, {2 * n_qubits})")
else:
depth = params_shape[0]
circuit = Id(qubit ** n_qubits).then(*(
layer(params[i]) for i in range(depth)))

return circuit
```