# Copyright 2019-2023 Cambridge Quantum Computing
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Set, Callable, Dict, FrozenSet
from pytket.circuit import Circuit, OpType
import pytket.circuit_library as _library
from pytket.passes import RebaseCustom, SquashCustom, SquashRzPhasedX
from ._decompositions import Param, _TK1_to_X_SX_Rz, _TK1_to_RxRy, _TK1_to_U
from .._tket.passes import BasePass
class NoAutoRebase(Exception):
"""Automatic rebase could not be found."""
_CX_CIRCS: Dict[OpType, Callable[[], "Circuit"]] = {
OpType.CX: _library.CX,
OpType.ZZMax: _library.CX_using_ZZMax,
OpType.XXPhase: _library.CX_using_XXPhase_0,
OpType.ECR: _library.CX_using_ECR,
OpType.CZ: _library.H_CZ_H,
}
def _TK2_using_TK2(a: Param, b: Param, c: Param) -> Circuit:
return Circuit(2).TK2(a, b, c, 0, 1)
_TK2_CIRCS: Dict[OpType, Callable[[Param, Param, Param], "Circuit"]] = {
OpType.TK2: _TK2_using_TK2,
OpType.ZZPhase: _library.TK2_using_ZZPhase,
OpType.CX: _library.TK2_using_CX,
OpType.ZZMax: _library.TK2_using_ZZMax,
}
_TK2_CIRCS_WIRE_SWAP: Dict[OpType, Callable[[Param, Param, Param], "Circuit"]] = {
OpType.TK2: _library.TK2_using_TK2_or_swap,
OpType.ZZPhase: _library.TK2_using_ZZPhase_and_swap,
OpType.CX: _library.TK2_using_CX_and_swap,
OpType.ZZMax: _library.TK2_using_ZZMax_and_swap,
}
def get_cx_decomposition(gateset: Set[OpType]) -> Circuit:
"""Return a Circuit expressing a CX in terms of a two qubit gate in the
gateset if one is available, raise an error otherwise.
:param gateset: Target gate set.
:type gateset: Set[OpType]
:raises NoAutoRebase: No suitable CX decomposition found.
:return: Decomposition circuit.
:rtype: Circuit
"""
if any((matching := k) in gateset for k in _CX_CIRCS):
return _CX_CIRCS[matching]()
raise NoAutoRebase("No known decomposition from CX to available gateset.")
def get_tk2_decomposition(
gateset: Set[OpType],
allow_swaps: bool,
) -> Callable[[Param, Param, Param], "Circuit"]:
"""Return a function to construct a circuit expressing a TK2 in terms of gates in
the given gateset, if such a function is available.
:param gateset: target gate set
:raises NoAutoRebase: no suitable TK2 decomposition found
:return: function to decompose TK2 gates
"""
if allow_swaps:
for k, fn in _TK2_CIRCS_WIRE_SWAP.items():
if k in gateset:
return fn
else:
for k, fn in _TK2_CIRCS.items():
if k in gateset:
return fn
raise NoAutoRebase("No known decomposition from TK2 to given gateset")
_TK1_circs: Dict[FrozenSet[OpType], Callable[[Param, Param, Param], "Circuit"]] = {
frozenset({OpType.TK1}): _library.TK1_to_TK1,
frozenset({OpType.PhasedX, OpType.Rz}): _library.TK1_to_PhasedXRz,
frozenset({OpType.Rx, OpType.Rz}): _library.TK1_to_RzRx,
frozenset({OpType.Ry, OpType.Rx}): _TK1_to_RxRy,
frozenset({OpType.Rz, OpType.H}): _library.TK1_to_RzH,
frozenset({OpType.Rz, OpType.SX, OpType.X}): _TK1_to_X_SX_Rz,
frozenset({OpType.Rz, OpType.SX}): _TK1_to_X_SX_Rz,
frozenset({OpType.Rz, OpType.SX}): _library.TK1_to_RzSX,
frozenset({OpType.U3}): _TK1_to_U,
}
def get_TK1_decomposition_function(
gateset: Set[OpType],
) -> Callable[[Param, Param, Param], "Circuit"]:
"""Return a function for generating TK1 equivalent circuits, which take the
three TK1 parameters as arguments and return a TK1 equivalent single qubit
circuit. If no such function is available, raise an error.
:raises NoAutoRebase: No suitable TK1 decomposition found.
:return: TK1 decomposition function.
:rtype: Callable[[Param, Param, Param], "Circuit"]
"""
subsets = [k for k in _TK1_circs if k.issubset(gateset)]
if subsets:
# find the largest available subset
# as in general more available gates leads to smaller circuits
matching = max(subsets, key=len)
return _TK1_circs[matching]
raise NoAutoRebase("No known decomposition from TK1 to available gateset.")
[docs]def auto_rebase_pass(gateset: Set[OpType], allow_swaps: bool = False) -> BasePass:
"""Attempt to generate a rebase pass automatically for the given target
gateset.
Checks if there are known existing decompositions
to target gateset and TK1 to target gateset and uses those to construct a
custom rebase.
Raises an error if no known decompositions can be found, in which case try
using RebaseCustom with your own decompositions.
:param gateset: Set of supported OpTypes, target gate set.
:type gateset: FrozenSet[OpType]
:raises NoAutoRebase: No suitable decomposition found.
:return: Rebase pass.
:rtype: RebaseCustom
"""
tk1 = get_TK1_decomposition_function(gateset)
# if the gateset has CX but not TK2, and implicit wire swaps not allowed:
# rebase via CX
if OpType.CX in gateset and OpType.TK2 not in gateset and not allow_swaps:
return RebaseCustom(gateset, _library.CX(), tk1)
# in other cases, try to rebase via TK2 first
try:
return RebaseCustom(gateset, get_tk2_decomposition(gateset, allow_swaps), tk1)
except NoAutoRebase:
pass
try:
return RebaseCustom(gateset, get_cx_decomposition(gateset), tk1)
except NoAutoRebase:
raise NoAutoRebase(
"No known decomposition from CX or TK2 to available gateset."
)
[docs]def auto_squash_pass(gateset: Set[OpType]) -> BasePass:
"""Attempt to generate a squash pass automatically for the given target
single qubit gateset.
:param gateset: Available single qubit gateset
:type gateset: Set[OpType]
:return: Squash to target gateset
:rtype: SquashCustom
"""
if {OpType.Rz, OpType.PhasedX} <= gateset:
return SquashRzPhasedX()
return SquashCustom(gateset, get_TK1_decomposition_function(gateset))
