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circuit_to_instruction.py
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circuit_to_instruction.py
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# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2019.
#
# 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.
"""Helper function for converting a circuit to an instruction."""
from qiskit.exceptions import QiskitError
from qiskit.circuit.instruction import Instruction
from qiskit.circuit.quantumregister import QuantumRegister, Qubit
from qiskit.circuit.classicalregister import ClassicalRegister
def circuit_to_instruction(circuit, parameter_map=None, equivalence_library=None):
"""Build an ``Instruction`` object from a ``QuantumCircuit``.
The instruction is anonymous (not tied to a named quantum register),
and so can be inserted into another circuit. The instruction will
have the same string name as the circuit.
Args:
circuit (QuantumCircuit): the input circuit.
parameter_map (dict): For parameterized circuits, a mapping from
parameters in the circuit to parameters to be used in the instruction.
If None, existing circuit parameters will also parameterize the
instruction.
equivalence_library (EquivalenceLibrary): Optional equivalence library
where the converted instruction will be registered.
Raises:
QiskitError: if parameter_map is not compatible with circuit
Return:
qiskit.circuit.Instruction: an instruction equivalent to the action of the
input circuit. Upon decomposition, this instruction will
yield the components comprising the original circuit.
Example:
.. jupyter-execute::
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.converters import circuit_to_instruction
%matplotlib inline
q = QuantumRegister(3, 'q')
c = ClassicalRegister(3, 'c')
circ = QuantumCircuit(q, c)
circ.h(q[0])
circ.cx(q[0], q[1])
circ.measure(q[0], c[0])
circ.rz(0.5, q[1]).c_if(c, 2)
circuit_to_instruction(circ)
"""
if parameter_map is None:
parameter_dict = {p: p for p in circuit.parameters}
else:
parameter_dict = circuit._unroll_param_dict(parameter_map)
if parameter_dict.keys() != circuit.parameters:
raise QiskitError(('parameter_map should map all circuit parameters. '
'Circuit parameters: {}, parameter_map: {}').format(
circuit.parameters, parameter_dict))
instruction = Instruction(name=circuit.name,
num_qubits=sum([qreg.size for qreg in circuit.qregs]),
num_clbits=sum([creg.size for creg in circuit.cregs]),
params=sorted(parameter_dict.values(), key=lambda p: p.name))
instruction.condition = None
def find_bit_position(bit):
"""find the index of a given bit (Register, int) within
a flat ordered list of bits of the circuit
"""
if isinstance(bit, Qubit):
ordered_regs = circuit.qregs
else:
ordered_regs = circuit.cregs
reg_index = ordered_regs.index(bit.register)
return sum([reg.size for reg in ordered_regs[:reg_index]]) + bit.index
target = circuit.assign_parameters(parameter_dict, inplace=False)
if equivalence_library is not None:
equivalence_library.add_equivalence(instruction, target)
definition = target.data
if instruction.num_qubits > 0:
q = QuantumRegister(instruction.num_qubits, 'q')
if instruction.num_clbits > 0:
c = ClassicalRegister(instruction.num_clbits, 'c')
definition = list(map(lambda x:
(x[0],
list(map(lambda y: q[find_bit_position(y)], x[1])),
list(map(lambda y: c[find_bit_position(y)], x[2]))), definition))
instruction.definition = definition
return instruction