Merge pull request #236 from ermalrrapaj/power_gate

Power gate

Author: edyounis

.pre-commit-config.yaml

@@ -2,7 +2,7 @@ ci:
     skip: [mypy]
 repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.4.0
+    rev: v4.6.0
     hooks:
     -   id: trailing-whitespace
     -   id: end-of-file-fixer
@@ -30,7 +30,7 @@ repos:
             - --wrap-summaries=80
             - --wrap-descriptions=80
 -   repo: https://github.com/pre-commit/mirrors-autopep8
-    rev: v2.0.2
+    rev: v2.0.4
     hooks:
     -   id: autopep8
         args:
@@ -39,13 +39,13 @@ repos:
             - --ignore=E731
         exclude: 'tests/ext.*'
 -   repo: https://github.com/asottile/pyupgrade
-    rev: v3.10.1
+    rev: v3.17.0
     hooks:
     -   id: pyupgrade
         args:
             - --py38-plus
 -   repo: https://github.com/asottile/reorder_python_imports
-    rev: v3.10.0
+    rev: v3.13.0
     hooks:
     -   id: reorder-python-imports
         args:
@@ -54,25 +54,25 @@ repos:
             - --py37-plus
         exclude: 'tests/ext.*'
 -   repo: https://github.com/asottile/add-trailing-comma
-    rev: v3.0.1
+    rev: v3.1.0
     hooks:
     -   id: add-trailing-comma
         args:
             - --py36-plus
 - repo: https://github.com/PyCQA/autoflake
-  rev: v2.2.0
+  rev: v2.3.1
   hooks:
     - id: autoflake
       args:
         - --in-place
 -   repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.5.0
+    rev: v1.11.1
     hooks:
     - id: mypy
       exclude: tests/qis/test_pauli.py
       additional_dependencies: ["numpy>=1.21"]
 -   repo: https://github.com/PyCQA/flake8
-    rev: 6.1.0
+    rev: 7.1.1
     hooks:
     -   id: flake8
         args:

bqskit/ext/qiskit/models.py

@@ -23,7 +23,7 @@ def model_from_backend(backend: BackendV1) -> MachineModel:
     num_qudits = config.n_qubits
     gate_set = _basis_gate_str_to_bqskit_gate(config.basis_gates)
     coupling_map = list({tuple(sorted(e)) for e in config.coupling_map})
-    return MachineModel(num_qudits, coupling_map, gate_set)  # type: ignore
+    return MachineModel(num_qudits, coupling_map, gate_set)
 
 
 def _basis_gate_str_to_bqskit_gate(basis_gates: list[str]) -> set[Gate]:

bqskit/ir/gates/__init__.py

@@ -100,6 +100,7 @@
     :template: autosummary/gate.rst
 
     ControlledGate
+    PowerGate
     DaggerGate
     EmbeddedGate
     FrozenParameterGate

bqskit/ir/gates/composed/__init__.py

@@ -5,11 +5,13 @@
 from bqskit.ir.gates.composed.daggergate import DaggerGate
 from bqskit.ir.gates.composed.embedded import EmbeddedGate
 from bqskit.ir.gates.composed.frozenparam import FrozenParameterGate
+from bqskit.ir.gates.composed.powergate import PowerGate
 from bqskit.ir.gates.composed.tagged import TaggedGate
 from bqskit.ir.gates.composed.vlg import VariableLocationGate
 
 __all__ = [
     'ControlledGate',
+    'PowerGate',
     'DaggerGate',
     'EmbeddedGate',
     'FrozenParameterGate',

bqskit/ir/gates/composed/powergate.py

@@ -0,0 +1,155 @@
+"""This module implements the DaggerGate Class."""
+from __future__ import annotations
+
+import re
+
+import numpy as np
+import numpy.typing as npt
+
+from bqskit.ir.gate import Gate
+from bqskit.ir.gates.composed.daggergate import DaggerGate
+from bqskit.ir.gates.composedgate import ComposedGate
+from bqskit.qis.unitary.differentiable import DifferentiableUnitary
+from bqskit.qis.unitary.unitary import RealVector
+from bqskit.qis.unitary.unitarymatrix import UnitaryMatrix
+from bqskit.utils.docs import building_docs
+from bqskit.utils.typing import is_integer
+
+
+class PowerGate(
+    ComposedGate,
+    DifferentiableUnitary,
+):
+    """
+    An arbitrary inverted gate.
+
+    The PowerGate is a composed gate that equivalent to the
+    integer power of the input gate.
+
+    Examples:
+        >>> from bqskit.ir.gates import TGate, TdgGate
+        >>> PowerGate(TGate(),2).get_unitary() ==
+           TdgGate().get_unitary()*TdgGate().get_unitary()
+        True
+    """
+
+    def __init__(self, gate: Gate, power: int = 1) -> None:
+        """
+        Create a gate which is the integer power of the input gate.
+
+        Args:
+            gate (Gate): The Gate to conjugate transpose.
+            power (int): The power index for the PowerGate.
+        """
+        if not isinstance(gate, Gate):
+            raise TypeError('Expected gate object, got %s' % type(gate))
+
+        if not is_integer(power):
+            raise TypeError(f'Expected integer power, got {type(power)}.')
+
+        self.gate = gate
+        self.power = power
+        self._name = f'[{gate.name}^{power}]'
+        self._num_params = gate.num_params
+        self._num_qudits = gate.num_qudits
+        self._radixes = gate.radixes
+
+        # If input is a constant gate, we can cache the unitary.
+        if self.num_params == 0 and not building_docs():
+            self.utry = self.gate.get_unitary([]).ipower(power)
+
+    def get_unitary(self, params: RealVector = []) -> UnitaryMatrix:
+        """Return the unitary for this gate, see :class:`Unitary` for more."""
+        if hasattr(self, 'utry'):
+            return self.utry
+
+        return self.gate.get_unitary(params).ipower(self.power)
+
+    def get_grad(self, params: RealVector = []) -> npt.NDArray[np.complex128]:
+        """
+        Return the gradient for this gate.
+
+        See :class:`DifferentiableUnitary` for more info.
+
+        Notes:
+            The derivative of the integer power of matrix is equal
+            to the derivative of the matrix multiplied by
+            the integer-1 power of the matrix
+            and by the integer power.
+        """
+        if hasattr(self, 'utry'):
+            return np.array([])
+
+        _, grad = self.get_unitary_and_grad(params)
+        return grad
+
+    def get_unitary_and_grad(
+        self,
+        params: RealVector = [],
+    ) -> tuple[UnitaryMatrix, npt.NDArray[np.complex128]]:
+        """
+        Return the unitary and gradient for this gate.
+
+        See :class:`DifferentiableUnitary` for more info.
+        """
+        # Constant gate case
+        if hasattr(self, 'utry'):
+            return self.utry, np.array([])
+
+        grad_shape = (self.num_params, self.dim, self.dim)
+
+        # Identity gate case
+        if self.power == 0:
+            utry = UnitaryMatrix.identity(self.dim)
+            grad = np.zeros(grad_shape, dtype=np.complex128)
+            return utry, grad
+
+        # Invert the gate if the power is negative
+        gate = self.gate if self.power > 0 else DaggerGate(self.gate)
+        power = abs(self.power)
+
+        # Parallel Dicts for unitary and gradient powers
+        utrys = {}  # utrys[i] = gate^(2^i)
+        grads = {}  # grads[i] = d(gate^(2^i))/d(params)
+
+        # decompose the power as sum of powers of 2
+        power_bin = bin(abs(power))[2:]
+        binary_decomp = [
+            len(power_bin) - 1 - xb.start()
+            for xb in re.finditer('1', power_bin)
+        ][::-1]
+        max_power_of_2 = max(binary_decomp)
+
+        # Base Case: 2^0
+        utrys[0], grads[0] = gate.get_unitary_and_grad(params)  # type: ignore
+
+        # Loop over powers of 2
+        for i in range(1, max_power_of_2 + 1):
+            # u^(2^i) = u^(2^(i-1)) @ u^(2^(i-1))
+            utrys[i] = utrys[i - 1] @ utrys[i - 1]
+
+            # d[u^(2^i)] = d[u^(2^(i-1)) @ u^(2^(i-1))] =
+            grads[i] = grads[i - 1] @ utrys[i - 1] + utrys[i - 1] @ grads[i - 1]
+
+        # Calculate binary composition of the unitary and gradient
+        utry = utrys[binary_decomp[0]]
+        grad = grads[binary_decomp[0]]
+        for i in sorted(binary_decomp[1:]):
+            grad = grad @ utrys[i] + utry @ grads[i]
+            utry = utry @ utrys[i]
+
+        return utry, grad
+
+    def __eq__(self, other: object) -> bool:
+        return (
+            isinstance(other, PowerGate)
+            and self.gate == other.gate
+            and self.power == other.power
+        )
+
+    def __hash__(self) -> int:
+        return hash((self.power, self.gate))
+
+    def get_inverse(self) -> Gate:
+        """Return the gate's inverse as a gate."""
+        return PowerGate(self.gate, -self.power)

bqskit/ir/interval.py

@@ -89,7 +89,7 @@ def __new__(
                 'Expected positive integers, got {lower} and {upper}.',
             )
 
-        return super().__new__(cls, (lower, upper))  # type: ignore
+        return super().__new__(cls, (lower, upper))
 
     @property
     def lower(self) -> int:

bqskit/ir/point.py

@@ -66,7 +66,7 @@ def __new__(
         else:
             raise TypeError('Expected two integer arguments.')
 
-        return super().__new__(cls, (cycle, qudit))  # type: ignore
+        return super().__new__(cls, (cycle, qudit))
 
     @property
     def cycle(self) -> int:

bqskit/qis/state/state.py

@@ -433,4 +433,8 @@ def __repr__(self) -> str:
         return repr(self._vec)
 
 
-StateLike = Union[StateVector, np.ndarray, Sequence[Union[int, float, complex]]]
+StateLike = Union[
+    StateVector,
+    npt.NDArray[np.complex128],
+    Sequence[Union[int, float, complex]],
+]

bqskit/qis/unitary/unitary.py

@@ -7,6 +7,7 @@
 from typing import Union
 
 import numpy as np
+import numpy.typing as npt
 
 from bqskit.qis.unitary.meta import UnitaryMeta
 from bqskit.utils.typing import is_real_number
@@ -151,4 +152,8 @@ def is_self_inverse(self, params: RealVector = []) -> bool:
         return np.allclose(unitary_matrix, hermitian_conjugate)
 
 
-RealVector = Union[Sequence[float], np.ndarray]
+RealVector = Union[
+    Sequence[float],
+    npt.NDArray[np.float64],
+    npt.NDArray[np.float32],
+]

bqskit/qis/unitary/unitarymatrix.py

@@ -199,6 +199,22 @@ def otimes(self, *utrys: UnitaryLike) -> UnitaryMatrix:
 
         return UnitaryMatrix(utry_acm, radixes_acm)
 
+    def ipower(self, power: int) -> UnitaryMatrix:
+        """
+        Calculate the integer power of this unitary.
+
+        Args:
+            power (int): The integer power to raise the unitary to.
+
+        Returns:
+            UnitaryMatrix: The resulting unitary matrix.
+        """
+        if power < 0:
+            mat = np.linalg.matrix_power(self.dagger, -power)
+        else:
+            mat = np.linalg.matrix_power(self, power)
+        return UnitaryMatrix(mat, self.radixes)
+
     def get_unitary(self, params: RealVector = []) -> UnitaryMatrix:
         """Return the same object, satisfies the :class:`Unitary` API."""
         return self
@@ -232,6 +248,23 @@ def get_distance_from(self, other: UnitaryLike, degree: int = 2) -> float:
         dist = np.power(1 - (frac ** degree), 1.0 / degree)
         return dist if dist > 0.0 else 0.0
 
+    def isclose(self, other: UnitaryLike, tol: float = 1e-6) -> bool:
+        """
+        Check if `self` is approximately equal to `other` upto global phase.
+
+        Args:
+            other (UnitaryLike): The unitary to compare to.
+
+            tol (float): The numerical precision of the check.
+
+        Returns:
+            bool: True if `self` is close to `other`.
+
+        See Also:
+            - :func:`get_distance_from` for the error function used.
+        """
+        return self.get_distance_from(other) < tol
+
     def get_statevector(self, in_state: StateLike) -> StateVector:
         """
         Calculate the output state after applying this unitary to `in_state`.
@@ -507,6 +540,11 @@ def __hash__(self) -> int:
 
 UnitaryLike = Union[
     UnitaryMatrix,
-    np.ndarray,
+    npt.NDArray[np.complex128],
+    npt.NDArray[np.complex64],
+    npt.NDArray[np.int64],
+    npt.NDArray[np.int32],
+    npt.NDArray[np.float64],
+    npt.NDArray[np.float32],
     Sequence[Sequence[Union[int, float, complex]]],
 ]