"""
Shortcuts for reusable circuit ansatz
"""
from typing import Any, List
from ..circuit import Circuit as Circ
Tensor = Any
Circuit = Any
[文档]def QAOA_ansatz_for_Ising(
params: List[float],
nlayers: int,
pauli_terms: Tensor,
weights: List[float],
full_coupling: bool = False,
mixer: str = "X",
) -> Circuit:
"""
Construct the QAOA ansatz for the Ising Model.
The number of qubits is determined by `pauli_terms`.
:param params: A list of parameter values used in the QAOA ansatz.
:param nlayers: The number of layers in the QAOA ansatz.
:pauli_terms: A list of Pauli terms, where each term is represented as a list of 0/1 series.
:param weights: A list of weights corresponding to each Pauli term.
:param full_coupling (optional): A flag indicating whether to use all-to-all coupling in mixers. Default is False.
:paran mixer (optional): The mixer operator to use. Default is "X". The other options are "XY" and "ZZ".
:return: QAOA ansatz for Ising model.
"""
nqubits = len(pauli_terms[0])
c: Any = Circ(nqubits)
for i in range(nqubits):
c.h(i) # Apply Hadamard gate to each qubit
for j in range(nlayers):
# cost terms
for k, term in enumerate(pauli_terms):
index_of_ones = []
for l in range(len(term)):
if term[l] == 1:
index_of_ones.append(l)
if len(index_of_ones) == 1:
c.rz(index_of_ones[0], theta=2 * weights[k] * params[2 * j])
# Apply Rz gate with angle determined by weight and current parameter value
elif len(index_of_ones) == 2:
c.rzz(
index_of_ones[0],
index_of_ones[1],
theta=weights[k] * params[2 * j],
)
# Apply exp1 gate with a custom unitary (zz_matrix)
# and angle determined by weight and current parameter value
else:
raise ValueError("Invalid number of Z terms")
# prepare the coupling map for mixer terms
pairs = []
if full_coupling is False:
for q0 in list(range(0, nqubits - 1, 2)) + list(range(1, nqubits - 1, 2)):
pairs.append([q0, q0 + 1])
pairs.append([nqubits - 1, 0])
elif full_coupling is True:
for q0 in range(nqubits - 1):
for q1 in range(q0 + 1, nqubits):
pairs.append([q0, q1])
else:
raise ValueError("Invalid input.")
# standard mixer
if mixer == "X":
for i in range(nqubits):
c.rx(
i, theta=params[2 * j + 1]
) # Apply Rx gate with angle determined by current parameter value
# XY mixer
elif mixer == "XY":
for [q0, q1] in pairs:
c.rxx(q0, q1, theta=params[2 * j + 1])
c.ryy(q0, q1, theta=params[2 * j + 1])
# ZZ mixer
elif mixer == "ZZ":
for [q0, q1] in pairs:
c.rzz(q0, q1, theta=params[2 * j + 1])
else:
raise ValueError("Invalid mixer type.")
return c