# Source code for cirq.ops.gate_features

# Copyright 2018 The Cirq Developers
#
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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# Unless required by applicable law or agreed to in writing, software
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"""Marker classes for indicating which additional features gates support.

For example: some gates are reversible, some have known matrices, etc.
"""

import abc

from cirq.ops import op_tree, raw_types

[docs]class InterchangeableQubitsGate(metaclass=abc.ABCMeta):
"""Indicates operations should be equal under some qubit permutations."""

[docs]    def qubit_index_to_equivalence_group_key(self, index: int) -> int:
"""Returns a key that differs between non-interchangeable qubits."""
return 0

[docs]class SingleQubitGate(raw_types.Gate, metaclass=abc.ABCMeta):
"""A gate that must be applied to exactly one qubit."""
[docs]    def num_qubits(self) -> int:
return 1

[docs]    def on_each(self, *targets: raw_types.Qid) -> op_tree.OP_TREE:
"""Returns a list of operations apply this gate to each of the targets.

Args:
*targets: The qubits to apply this gate to.

Returns:
Operations applying this gate to the target qubits.

Raises:
ValueError if targets are not instances of Qid.
"""
return [self.on(target) for target in targets]

[docs]class TwoQubitGate(raw_types.Gate, metaclass=abc.ABCMeta):
"""A gate that must be applied to exactly two qubits."""
[docs]    def num_qubits(self) -> int:
return 2

[docs]class ThreeQubitGate(raw_types.Gate, metaclass=abc.ABCMeta):
"""A gate that must be applied to exactly three qubits."""
[docs]    def num_qubits(self) -> int:
return 3