Source code for mitiq.benchmarks.w_state_circuits

# Copyright (C) Unitary Fund
# This source code is licensed under the GPL license (v3) found in the
# LICENSE file in the root directory of this source tree.

"""Functions for creating a linear complexity W-state benchmarking circuit
as defined in :cite:`Cruz_2019_Efficient`."""

from typing import Optional

import cirq
import numpy as np

from mitiq import QPROGRAM
from mitiq.interface import convert_from_mitiq

[docs]def generate_w_circuit( n_qubits: int, return_type: Optional[str] = None, ) -> QPROGRAM: """Returns a circuit to create a ``n_qubits`` qubit Werner-state with linear complexity as defined in :cite:`Cruz_2019_Efficient`. Args: n_qubits : The number of qubits in the circuit. return_type : Return type of the output circuit. Returns: A W-state circuit of linear complexity acting on ``n_qubits`` qubits. """ if n_qubits <= 0: raise ValueError("{} is invalid for the number of qubits. ", n_qubits) qubits = cirq.LineQubit.range(n_qubits) circuit = cirq.Circuit() for i, j in zip(range(0, n_qubits), range(1, n_qubits)): N = n_qubits - i angle = 2 * np.arccos(np.sqrt(1 / N)) circuit.append( cirq.Ry(rads=angle).controlled().on(qubits[i], qubits[j]) ) circuit.append(cirq.CNOT(qubits[j], qubits[i])) return_type = "cirq" if not return_type else return_type return convert_from_mitiq(circuit, return_type)