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* `Rz` via controlled-add-or-sub into phase gradient * docstring: reference * add tensor test * fix bug
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| # Copyright 2024 Google LLC | ||
| # | ||
| # 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 | ||
| # | ||
| # https://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 attrs import frozen | ||
|
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| from qualtran import ( | ||
| Bloq, | ||
| bloq_example, | ||
| BloqBuilder, | ||
| QBit, | ||
| QDType, | ||
| QUInt, | ||
| Signature, | ||
| Soquet, | ||
| SoquetT, | ||
| ) | ||
| from qualtran.bloqs.arithmetic.controlled_add_or_subtract import ControlledAddOrSubtract | ||
| from qualtran.bloqs.bookkeeping import Cast | ||
| from qualtran.resource_counting import BloqCountT, SympySymbolAllocator | ||
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| @frozen | ||
| class RzViaPhaseGradient(Bloq): | ||
| r"""Apply a controlled-Rz using a phase gradient state. | ||
| Implements the following unitary action: | ||
| $$ | ||
| |\psi\rangle \otimes |x\rangle \mapsto \text{Rz}(4 \pi x) |\psi\rangle \otimes |x\rangle | ||
| $$ | ||
| for every state $|\psi\rangle$ and every $x$, or equivalently | ||
| $$ | ||
| |b\rangle|x\rangle \mapsto |b\rangle e^{- (-1)^b i x/2} |x\rangle | ||
| $$ | ||
| for every $b \in \{0, 1\}$ and every $x$. | ||
| To apply an $\text{Rz}(\theta) = e^{-i Z \theta/2}$, the angle register $x$ should store $\theta/(4\pi)$. | ||
| Args: | ||
| angle_dtype: Data type for the `angle_data` register. | ||
| phasegrad_dtype: Data type for the phase gradient register. | ||
| Registers: | ||
| q: The qubit to apply Rz on. | ||
| angle: The rotation angle in radians. | ||
| phase_grad: The phase gradient register of sufficient width. | ||
| References: | ||
| [Compilation of Fault-Tolerant Quantum Heuristics for Combinatorial Optimization](https://arxiv.org/abs/2007.07391). | ||
| Section II-C: Oracles for phasing by cost function. | ||
| Appendix A: Addition for controlled rotations. | ||
| """ | ||
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| angle_dtype: QDType | ||
| phasegrad_dtype: QDType | ||
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| @property | ||
| def signature(self) -> Signature: | ||
| return Signature.build_from_dtypes( | ||
| q=QBit(), angle=self.angle_dtype, phase_grad=self.phasegrad_dtype | ||
| ) | ||
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| @property | ||
| def _angle_int_dtype(self) -> QUInt: | ||
| return QUInt(self.angle_dtype.num_qubits) | ||
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| @property | ||
| def _phasegrad_int_dtype(self) -> QUInt: | ||
| return QUInt(self.phasegrad_dtype.num_qubits) | ||
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| def build_composite_bloq( | ||
| self, bb: BloqBuilder, q: Soquet, angle: Soquet, phase_grad: Soquet | ||
| ) -> dict[str, SoquetT]: | ||
| angle = bb.add(Cast(self.angle_dtype, self._angle_int_dtype), reg=angle) | ||
| phase_grad = bb.add(Cast(self.phasegrad_dtype, self._phasegrad_int_dtype), reg=phase_grad) | ||
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| q, angle, phase_grad = bb.add( | ||
| ControlledAddOrSubtract(self._angle_int_dtype, self._phasegrad_int_dtype), | ||
| ctrl=q, | ||
| a=angle, | ||
| b=phase_grad, | ||
| ) | ||
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| angle = bb.add(Cast(self._angle_int_dtype, self.angle_dtype), reg=angle) | ||
| phase_grad = bb.add(Cast(self._phasegrad_int_dtype, self.phasegrad_dtype), reg=phase_grad) | ||
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| return {'q': q, 'angle': angle, 'phase_grad': phase_grad} | ||
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| def build_call_graph(self, ssa: 'SympySymbolAllocator') -> set['BloqCountT']: | ||
| return {(ControlledAddOrSubtract(self._angle_int_dtype, self._phasegrad_int_dtype), 1)} | ||
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| @bloq_example | ||
| def _rz_via_phase_gradient() -> RzViaPhaseGradient: | ||
| from qualtran import QFxp | ||
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| rz_via_phase_gradient = RzViaPhaseGradient(angle_dtype=QFxp(4, 4), phasegrad_dtype=QFxp(4, 4)) | ||
| return rz_via_phase_gradient |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| # Copyright 2024 Google LLC | ||
| # | ||
| # 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 | ||
| # | ||
| # https://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. | ||
| import numpy as np | ||
| import pytest | ||
| import sympy | ||
| from attrs import frozen | ||
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| from qualtran import Bloq, BloqBuilder, QBit, QFxp, QUInt, Signature, Soquet, SoquetT | ||
| from qualtran.bloqs.basic_gates import IntState, Rz, TGate | ||
| from qualtran.bloqs.rotations.phase_gradient import PhaseGradientState | ||
| from qualtran.bloqs.rotations.rz_via_phase_gradient import ( | ||
| _rz_via_phase_gradient, | ||
| RzViaPhaseGradient, | ||
| ) | ||
| from qualtran.resource_counting import BloqCount, get_cost_value | ||
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| def test_examples(bloq_autotester): | ||
| bloq_autotester(_rz_via_phase_gradient) | ||
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| def test_costs(): | ||
| n = sympy.Symbol("n") | ||
| dtype = QUInt(n) | ||
| bloq = RzViaPhaseGradient(angle_dtype=dtype, phasegrad_dtype=dtype) | ||
| # TODO need to improve this to `4 * n - 8` (i.e. Toffoli cost of `n - 2`) | ||
| assert get_cost_value(bloq, BloqCount.for_gateset('t')) == {TGate(): 4 * n - 4} | ||
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| @frozen | ||
| class TestRz(Bloq): | ||
| angle: float | ||
| phasegrad_bitsize: int = 4 | ||
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| @property | ||
| def signature(self) -> 'Signature': | ||
| return Signature.build_from_dtypes(q=QBit()) | ||
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| @property | ||
| def dtype(self) -> QFxp: | ||
| return QFxp(self.phasegrad_bitsize, self.phasegrad_bitsize) | ||
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| @property | ||
| def load_angle_bloq(self) -> IntState: | ||
| return IntState( | ||
| self.dtype.to_fixed_width_int(self.angle / (4 * np.pi), require_exact=False), | ||
| bitsize=self.phasegrad_bitsize, | ||
| ) | ||
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| @property | ||
| def load_phasegrad_bloq(self) -> PhaseGradientState: | ||
| return PhaseGradientState(self.phasegrad_bitsize) | ||
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| def build_composite_bloq(self, bb: 'BloqBuilder', q: Soquet) -> dict[str, 'SoquetT']: | ||
| angle = bb.add(self.load_angle_bloq) | ||
| phase_grad = bb.add(self.load_phasegrad_bloq) | ||
| q, angle, phase_grad = bb.add( | ||
| RzViaPhaseGradient(angle_dtype=self.dtype, phasegrad_dtype=self.dtype), | ||
| q=q, | ||
| angle=angle, | ||
| phase_grad=phase_grad, | ||
| ) | ||
| bb.add(self.load_angle_bloq.adjoint(), val=angle) | ||
| bb.add(self.load_phasegrad_bloq.adjoint(), phase_grad=phase_grad) | ||
| return {'q': q} | ||
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| @pytest.mark.parametrize("bitsize", [3, 4]) | ||
| def test_tensor(bitsize: int): | ||
| for coeff in [1, 2]: | ||
| theta = 4 * np.pi * coeff / 2**bitsize | ||
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| actual = TestRz(angle=theta, phasegrad_bitsize=bitsize).tensor_contract() | ||
| expected = Rz(theta).tensor_contract() | ||
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| np.testing.assert_allclose(actual, expected, atol=1 / 2**bitsize) |
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