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Implement dynamical decoupling. (#6515)
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‎cirq-core/cirq/__init__.py

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from cirq.transformers import (
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AbstractInitialMapper,
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add_dynamical_decoupling,
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align_left,
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align_right,
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CompilationTargetGateset,

‎cirq-core/cirq/transformers/__init__.py

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from cirq.transformers.drop_negligible_operations import drop_negligible_operations
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from cirq.transformers.dynamical_decoupling import add_dynamical_decoupling
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from cirq.transformers.eject_z import eject_z
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from cirq.transformers.measurement_transformers import (

‎cirq-core/cirq/transformers/dynamical_decoupling.py

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# Copyright 2024 The Cirq Developers
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Transformer pass that adds dynamical decoupling operations to a circuit."""
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from functools import reduce
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from typing import Dict, Optional, Sequence, Tuple, Union
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from cirq.transformers import transformer_api
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import cirq
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import numpy as np
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def _repeat_sequence(
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base_sequence: Sequence['cirq.Gate'], num_idle_moments: int
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) -> Sequence['cirq.Gate']:
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"""Returns the longest possible dynamical decoupling sequence."""
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repeat_times = num_idle_moments // len(base_sequence)
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return list(base_sequence) * repeat_times
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def _get_dd_sequence_from_schema_name(schema: str) -> Sequence['cirq.Gate']:
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"""Gets dynamical decoupling sequence from a schema name."""
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dd_sequence: Sequence['cirq.Gate']
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match schema:
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case 'XX_PAIR':
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dd_sequence = (cirq.X, cirq.X)
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case 'X_XINV':
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dd_sequence = (cirq.X, cirq.X**-1)
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case 'YY_PAIR':
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dd_sequence = (cirq.Y, cirq.Y)
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case 'Y_YINV':
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dd_sequence = (cirq.Y, cirq.Y**-1)
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case _:
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raise ValueError('Invalid schema name.')
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return dd_sequence
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def _validate_dd_sequence(dd_sequence: Sequence['cirq.Gate']) -> None:
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"""Validates a given dynamical decoupling sequence.
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Args:
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dd_sequence: Input dynamical sequence to be validated.
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Returns:
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A tuple containing:
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- is_valid (bool): True if the dd sequence is valid, False otherwise.
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- error_message (str): An error message if the dd sequence is invalid, else None.
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Raises:
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ValueError: If dd_sequence is not valid.
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"""
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if len(dd_sequence) < 2:
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raise ValueError('Invalid dynamical decoupling sequence. Expect more than one gates.')
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matrices = [cirq.unitary(gate) for gate in dd_sequence]
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product = reduce(np.matmul, matrices)
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if not cirq.equal_up_to_global_phase(product, np.eye(2)):
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raise ValueError(
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'Invalid dynamical decoupling sequence. Expect sequence production equals'
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f' identity up to a global phase, got {product}.'.replace('\n', ' ')
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)
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def _parse_dd_sequence(schema: Union[str, Sequence['cirq.Gate']]) -> Sequence['cirq.Gate']:
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"""Parses and returns dynamical decoupling sequence from schema."""
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if isinstance(schema, str):
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dd_sequence = _get_dd_sequence_from_schema_name(schema)
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else:
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_validate_dd_sequence(schema)
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dd_sequence = schema
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return dd_sequence
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@transformer_api.transformer
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def add_dynamical_decoupling(
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circuit: 'cirq.AbstractCircuit',
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*,
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context: Optional['cirq.TransformerContext'] = None,
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schema: Union[str, Sequence['cirq.Gate']] = 'X_XINV',
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) -> 'cirq.Circuit':
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"""Adds dynamical decoupling gate operations to idle moments of a given circuit.
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This transformer preserves the moment structure of the circuit.
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Args:
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circuit: Input circuit to transform.
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context: `cirq.TransformerContext` storing common configurable options for transformers.
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schema: Dynamical decoupling schema name or a dynamical decoupling sequence.
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If a schema is specified, provided dynamical decouping sequence will be used.
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Otherwise, customized dynamical decoupling sequence will be applied.
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Returns:
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A copy of the input circuit with dynamical decoupling operations.
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"""
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last_busy_moment_by_qubits: Dict['cirq.Qid', int] = {q: 0 for q in circuit.all_qubits()}
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insert_into: list[Tuple[int, 'cirq.OP_TREE']] = []
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base_dd_sequence = _parse_dd_sequence(schema)
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for moment_id, moment in enumerate(circuit):
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for q in moment.qubits:
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insert_gates = _repeat_sequence(
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base_dd_sequence, num_idle_moments=moment_id - last_busy_moment_by_qubits[q] - 1
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)
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for idx, gate in enumerate(insert_gates):
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insert_into.append((last_busy_moment_by_qubits[q] + idx + 1, gate.on(q)))
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last_busy_moment_by_qubits[q] = moment_id
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updated_circuit = circuit.unfreeze(copy=True)
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updated_circuit.batch_insert_into(insert_into)
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return updated_circuit

‎cirq-core/cirq/transformers/dynamical_decoupling_test.py

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# Copyright 2024 The Cirq Developers
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from typing import Sequence, Union
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import cirq
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from cirq import add_dynamical_decoupling
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import pytest
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def assert_dd(
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input_circuit: cirq.Circuit,
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expected_circuit: cirq.Circuit,
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schema: Union[str, Sequence['cirq.Gate']],
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):
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updated_circuit = add_dynamical_decoupling(input_circuit, schema=schema)
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cirq.testing.assert_same_circuits(updated_circuit, expected_circuit)
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def test_no_insert_due_to_no_consecutive_moments():
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a = cirq.NamedQubit('a')
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b = cirq.NamedQubit('b')
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# No insertion as there is no room for a dd sequence.
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assert_dd(
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input_circuit=cirq.Circuit(
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cirq.Moment(cirq.H(a)), cirq.Moment(cirq.CNOT(a, b)), cirq.Moment(cirq.H(b))
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),
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expected_circuit=cirq.Circuit(
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cirq.Moment(cirq.H(a)), cirq.Moment(cirq.CNOT(a, b)), cirq.Moment(cirq.H(b))
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),
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schema='XX_PAIR',
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)
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@pytest.mark.parametrize(
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'schema,inserted_gates',
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[
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('XX_PAIR', (cirq.X, cirq.X)),
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('X_XINV', (cirq.X, cirq.X**-1)),
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('YY_PAIR', (cirq.Y, cirq.Y)),
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('Y_YINV', (cirq.Y, cirq.Y**-1)),
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],
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)
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def test_insert_provided_schema(schema: str, inserted_gates: Sequence['cirq.Gate']):
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a = cirq.NamedQubit('a')
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b = cirq.NamedQubit('b')
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c = cirq.NamedQubit('c')
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input_circuit = cirq.Circuit(
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cirq.Moment(cirq.H(a)),
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cirq.Moment(cirq.CNOT(a, b)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.measure_each(a, b, c)),
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)
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expected_circuit = cirq.Circuit(
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cirq.Moment(cirq.H(a)),
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cirq.Moment(cirq.CNOT(a, b)),
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cirq.Moment(cirq.CNOT(b, c), inserted_gates[0](a)),
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cirq.Moment(cirq.CNOT(b, c), inserted_gates[1](a)),
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cirq.Moment(cirq.measure_each(a, b, c)),
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)
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# Insert one dynamical decoupling sequence in idle moments.
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assert_dd(input_circuit, expected_circuit, schema=schema)
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def test_insert_by_customized_dd_sequence():
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a = cirq.NamedQubit('a')
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b = cirq.NamedQubit('b')
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c = cirq.NamedQubit('c')
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assert_dd(
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input_circuit=cirq.Circuit(
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cirq.Moment(cirq.H(a)),
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cirq.Moment(cirq.CNOT(a, b)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.CNOT(b, c)),
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cirq.Moment(cirq.measure_each(a, b, c)),
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),
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expected_circuit=cirq.Circuit(
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cirq.Moment(cirq.H(a)),
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cirq.Moment(cirq.CNOT(a, b)),
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cirq.Moment(cirq.CNOT(b, c), cirq.X(a)),
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cirq.Moment(cirq.CNOT(b, c), cirq.X(a)),
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cirq.Moment(cirq.CNOT(b, c), cirq.Y(a)),
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cirq.Moment(cirq.CNOT(b, c), cirq.Y(a)),
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cirq.Moment(cirq.measure_each(a, b, c)),
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),
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schema=[cirq.X, cirq.X, cirq.Y, cirq.Y],
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)
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@pytest.mark.parametrize(
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'schema,error_msg_regex',
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[
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('INVALID_SCHEMA', 'Invalid schema name.'),
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([cirq.X], 'Invalid dynamical decoupling sequence. Expect more than one gates.'),
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(
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[cirq.X, cirq.H],
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'Invalid dynamical decoupling sequence. Expect sequence production equals identity'
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' up to a global phase, got',
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),
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],
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)
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def test_invalid_dd_schema(schema: Union[str, Sequence['cirq.Gate']], error_msg_regex):
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a = cirq.NamedQubit('a')
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input_circuit = cirq.Circuit(cirq.H(a))
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with pytest.raises(ValueError, match=error_msg_regex):
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add_dynamical_decoupling(input_circuit, schema=schema)

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