diff --git a/.github/CHANGELOG.md b/.github/CHANGELOG.md
index d607381fde..02116881ad 100644
--- a/.github/CHANGELOG.md
+++ b/.github/CHANGELOG.md
@@ -9,6 +9,9 @@
* Introduces requirements-dev.txt and improves dockerfile.
[(#330)](https://github.com/PennyLaneAI/pennylane-lightning/pull/330)
+* Support `expval` for a Hamiltonian.
+[(#333)](https://github.com/PennyLaneAI/pennylane-lightning/pull/333)
+
### Documentation
### Bug fixes
diff --git a/pennylane_lightning/_serialize.py b/pennylane_lightning/_serialize.py
index 309484ad3d..e0e546192a 100644
--- a/pennylane_lightning/_serialize.py
+++ b/pennylane_lightning/_serialize.py
@@ -27,6 +27,7 @@
from pennylane.grouping import is_pauli_word
from pennylane.operation import Observable, Tensor
from pennylane.tape import QuantumTape
+from pennylane.math import unwrap
# Remove after the next release of PL
# Add from pennylane import matrix
@@ -111,7 +112,7 @@ def _serialize_hamiltonian(ob, wires_map: dict, use_csingle: bool):
rtype = np.float64
hamiltonian_obs = HamiltonianC128
- coeffs = np.array(ob.coeffs).astype(rtype)
+ coeffs = np.array(unwrap(ob.coeffs)).astype(rtype)
terms = [_serialize_ob(t, wires_map, use_csingle) for t in ob.ops]
return hamiltonian_obs(coeffs, terms)
diff --git a/pennylane_lightning/_version.py b/pennylane_lightning/_version.py
index 35bb0bee32..41ac2b39c3 100644
--- a/pennylane_lightning/_version.py
+++ b/pennylane_lightning/_version.py
@@ -16,4 +16,4 @@
Version number (major.minor.patch[-label])
"""
-__version__ = "0.26.0-dev3"
+__version__ = "0.26.0-dev4"
diff --git a/pennylane_lightning/lightning_qubit.py b/pennylane_lightning/lightning_qubit.py
index c865756569..ce6159a279 100644
--- a/pennylane_lightning/lightning_qubit.py
+++ b/pennylane_lightning/lightning_qubit.py
@@ -57,7 +57,7 @@
best_alignment,
)
- from ._serialize import _serialize_observables, _serialize_ops
+ from ._serialize import _serialize_ob, _serialize_observables, _serialize_ops
CPP_BINARY_AVAILABLE = True
except ModuleNotFoundError:
@@ -621,8 +621,6 @@ def expval(self, observable, shot_range=None, bin_size=None):
if isinstance(observable.name, List) or observable.name in [
"Identity",
"Projector",
- "Hermitian",
- "Hamiltonian",
]:
return super().expval(observable, shot_range=shot_range, bin_size=bin_size)
@@ -648,6 +646,10 @@ def expval(self, observable, shot_range=None, bin_size=None):
)
return super().expval(observable, shot_range=shot_range, bin_size=bin_size)
+ if observable.name in ["Hamiltonian", "Hermitian"]:
+ ob_serialized = _serialize_ob(observable, self.wire_map, use_csingle=self.use_csingle)
+ return M.expval(ob_serialized)
+
# translate to wire labels used by device
observable_wires = self.map_wires(observable.wires)
diff --git a/pennylane_lightning/src/algorithms/AlgUtil.hpp b/pennylane_lightning/src/algorithms/AlgUtil.hpp
index 8e1f50a064..4ea92712e6 100644
--- a/pennylane_lightning/src/algorithms/AlgUtil.hpp
+++ b/pennylane_lightning/src/algorithms/AlgUtil.hpp
@@ -66,7 +66,7 @@ inline void applyOperationAdj(StateVectorManagedCPU<T> &state,
*/
template <typename T>
inline void applyObservable(StateVectorManagedCPU<T> &state,
- Observable<T> &observable) {
+ Simulators::Observable<T> &observable) {
observable.applyInPlace(state);
}
@@ -79,10 +79,11 @@ inline void applyObservable(StateVectorManagedCPU<T> &state,
* @param observables Vector of observables to apply to each statevector.
*/
template <typename T>
-inline void applyObservables(
- std::vector<StateVectorManagedCPU<T>> &states,
- const StateVectorManagedCPU<T> &reference_state,
- const std::vector<std::shared_ptr<Observable<T>>> &observables) {
+inline void
+applyObservables(std::vector<StateVectorManagedCPU<T>> &states,
+ const StateVectorManagedCPU<T> &reference_state,
+ const std::vector<std::shared_ptr<Simulators::Observable<T>>>
+ &observables) {
std::exception_ptr ex = nullptr;
size_t num_observables = observables.size();
diff --git a/pennylane_lightning/src/algorithms/CMakeLists.txt b/pennylane_lightning/src/algorithms/CMakeLists.txt
index 7b7bfca8d1..50e315a4fe 100644
--- a/pennylane_lightning/src/algorithms/CMakeLists.txt
+++ b/pennylane_lightning/src/algorithms/CMakeLists.txt
@@ -1,6 +1,6 @@
project(lightning_algorithms LANGUAGES CXX)
-set(ALGORITHM_FILES AdjointDiff.cpp Observables.cpp JacobianTape.cpp StateVecAdjDiff.cpp CACHE INTERNAL "" FORCE)
+set(ALGORITHM_FILES AdjointDiff.cpp JacobianTape.cpp StateVecAdjDiff.cpp CACHE INTERNAL "" FORCE)
add_library(lightning_algorithms STATIC ${ALGORITHM_FILES})
target_link_libraries(lightning_algorithms PRIVATE lightning_compile_options
diff --git a/pennylane_lightning/src/algorithms/JacobianTape.hpp b/pennylane_lightning/src/algorithms/JacobianTape.hpp
index 1c94696a1b..848db63950 100644
--- a/pennylane_lightning/src/algorithms/JacobianTape.hpp
+++ b/pennylane_lightning/src/algorithms/JacobianTape.hpp
@@ -206,7 +206,7 @@ template <class T> class JacobianData {
* @var observables
* Observables for which to calculate Jacobian.
*/
- const std::vector<std::shared_ptr<Observable<T>>> observables;
+ const std::vector<std::shared_ptr<Simulators::Observable<T>>> observables;
/**
* @var operations
@@ -238,7 +238,7 @@ template <class T> class JacobianData {
* @endrst
*/
JacobianData(size_t num_params, size_t num_elem, std::complex<T> *ps,
- std::vector<std::shared_ptr<Observable<T>>> obs,
+ std::vector<std::shared_ptr<Simulators::Observable<T>>> obs,
OpsData<T> ops, std::vector<size_t> trainP)
: num_parameters(num_params), num_elements(num_elem), psi(ps),
observables(std::move(obs)), operations(std::move(ops)),
@@ -278,7 +278,7 @@ template <class T> class JacobianData {
* @return List of observables
*/
[[nodiscard]] auto getObservables() const
- -> const std::vector<std::shared_ptr<Observable<T>>> & {
+ -> const std::vector<std::shared_ptr<Simulators::Observable<T>>> & {
return observables;
}
diff --git a/pennylane_lightning/src/bindings/Bindings.cpp b/pennylane_lightning/src/bindings/Bindings.cpp
index 9ec619c7b4..92caecefe9 100644
--- a/pennylane_lightning/src/bindings/Bindings.cpp
+++ b/pennylane_lightning/src/bindings/Bindings.cpp
@@ -18,6 +18,7 @@
#include "Bindings.hpp"
#include "GateUtil.hpp"
+#include "Measures.hpp"
#include "StateVecAdjDiff.hpp"
#include "StateVectorManagedCPU.hpp"
@@ -27,6 +28,7 @@
namespace {
using namespace Pennylane;
using namespace Pennylane::Util;
+using namespace Pennylane::Simulators;
using namespace Pennylane::Algorithms;
using namespace Pennylane::Gates;
@@ -95,6 +97,13 @@ void lightning_class_bindings(py::module_ &m) {
const std::string &, const std::vector<size_t> &)>(
&Measures<PrecisionT>::expval),
"Expected value of an operation by name.")
+ .def(
+ "expval",
+ [](Measures<PrecisionT> &M,
+ const std::shared_ptr<Observable<PrecisionT>> &ob) {
+ return M.expval(*ob);
+ },
+ "Expected value of an operation object.")
.def(
"expval",
[](Measures<PrecisionT> &M, const np_arr_sparse_ind row_map,
@@ -413,7 +422,7 @@ PYBIND11_MODULE(lightning_qubit_ops, // NOLINT: No control over Pybind internals
/* Add compile info */
m.def("compile_info", &getCompileInfo, "Compiled binary information.");
- /* Add compile info */
+ /* Add runtime info */
m.def("runtime_info", &getRuntimeInfo, "Runtime information.");
/* Add Kokkos and Kokkos Kernels info */
diff --git a/pennylane_lightning/src/simulator/CMakeLists.txt b/pennylane_lightning/src/simulator/CMakeLists.txt
index 50da06f71c..e1ea946e93 100644
--- a/pennylane_lightning/src/simulator/CMakeLists.txt
+++ b/pennylane_lightning/src/simulator/CMakeLists.txt
@@ -1,23 +1,13 @@
project(lightning_simulator)
-set(SIMULATOR_FILES StateVectorRawCPU.cpp StateVectorManagedCPU.cpp Measures.cpp CACHE INTERNAL "" FORCE)
+set(SIMULATOR_FILES StateVectorRawCPU.cpp Observables.cpp StateVectorManagedCPU.cpp Measures.cpp CACHE INTERNAL "" FORCE)
add_library(lightning_simulator STATIC ${SIMULATOR_FILES})
if (UNIX AND (${CMAKE_SYSTEM_PROCESSOR} MATCHES "(AMD64)|(X64)|(x64)|(x86_64)"))
- add_library(lightning_simulator_assign_kernels_x64 STATIC KernelMap_X64.cpp AssignKernelMap_AVX2.cpp AssignKernelMap_AVX512.cpp AssignKernelMap_Default.cpp)
- target_link_libraries(lightning_simulator_assign_kernels_x64 PRIVATE lightning_compile_options
- lightning_external_libs
- lightning_gates
- lightning_utils)
- target_link_libraries(lightning_simulator PRIVATE lightning_simulator_assign_kernels_x64)
+ target_sources(lightning_simulator PRIVATE KernelMap_X64.cpp AssignKernelMap_AVX2.cpp AssignKernelMap_AVX512.cpp AssignKernelMap_Default.cpp)
else()
- add_library(lightning_simulator_assign_kernels_default STATIC KernelMap_Default.cpp AssignKernelMap_Default.cpp)
- target_link_libraries(lightning_simulator_assign_kernels_default PRIVATE lightning_compile_options
- lightning_external_libs
- lightning_gates
- lightning_utils)
- target_link_libraries(lightning_simulator PRIVATE lightning_simulator_assign_kernels_default)
+ target_sources(lightning_simulator PRIVATE KernelMap_Default.cpp AssignKernelMap_Default.cpp)
endif()
target_include_directories(lightning_simulator PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/pennylane_lightning/src/simulator/Measures.cpp b/pennylane_lightning/src/simulator/Measures.cpp
index c817639950..513b898f51 100644
--- a/pennylane_lightning/src/simulator/Measures.cpp
+++ b/pennylane_lightning/src/simulator/Measures.cpp
@@ -15,6 +15,7 @@
#include "Measures.hpp"
// explicit instantiation
-template class Pennylane::Measures<float, Pennylane::StateVectorRawCPU<float>>;
-template class Pennylane::Measures<double,
- Pennylane::StateVectorRawCPU<double>>;
+template class Pennylane::Simulators::Measures<
+ float, Pennylane::StateVectorRawCPU<float>>;
+template class Pennylane::Simulators::Measures<
+ double, Pennylane::StateVectorRawCPU<double>>;
diff --git a/pennylane_lightning/src/simulator/Measures.hpp b/pennylane_lightning/src/simulator/Measures.hpp
index e0d2d53f0c..d053e4359a 100644
--- a/pennylane_lightning/src/simulator/Measures.hpp
+++ b/pennylane_lightning/src/simulator/Measures.hpp
@@ -30,10 +30,11 @@
#include "Kokkos_Sparse.hpp"
#include "LinearAlgebra.hpp"
+#include "Observables.hpp"
#include "StateVectorManagedCPU.hpp"
#include "StateVectorRawCPU.hpp"
-namespace Pennylane {
+namespace Pennylane::Simulators {
/**
* @brief Observable's Measurement Class.
@@ -217,6 +218,20 @@ class Measures {
return expected_value_list;
}
+ /**
+ * @brief Expectation value for a general Observable
+ *
+ * @param ob Observable
+ */
+ auto expval(const Observable<fp_t> &ob) -> fp_t {
+ StateVectorManagedCPU<fp_t> op_sv(original_statevector);
+ ob.applyInPlace(op_sv);
+ const auto inner_prod =
+ Util::innerProdC(original_statevector.getData(), op_sv.getData(),
+ original_statevector.getLength());
+ return std::real(inner_prod);
+ }
+
/**
* @brief Variance of an observable.
*
@@ -380,4 +395,4 @@ class Measures {
return samples;
}
}; // class Measures
-} // namespace Pennylane
+} // namespace Pennylane::Simulators
diff --git a/pennylane_lightning/src/algorithms/Observables.cpp b/pennylane_lightning/src/simulator/Observables.cpp
similarity index 57%
rename from pennylane_lightning/src/algorithms/Observables.cpp
rename to pennylane_lightning/src/simulator/Observables.cpp
index d784910db0..8b200a2651 100644
--- a/pennylane_lightning/src/algorithms/Observables.cpp
+++ b/pennylane_lightning/src/simulator/Observables.cpp
@@ -14,14 +14,14 @@
#include "Observables.hpp"
-template class Pennylane::Algorithms::NamedObs<float>;
-template class Pennylane::Algorithms::NamedObs<double>;
+template class Pennylane::Simulators::NamedObs<float>;
+template class Pennylane::Simulators::NamedObs<double>;
-template class Pennylane::Algorithms::HermitianObs<float>;
-template class Pennylane::Algorithms::HermitianObs<double>;
+template class Pennylane::Simulators::HermitianObs<float>;
+template class Pennylane::Simulators::HermitianObs<double>;
-template class Pennylane::Algorithms::TensorProdObs<float>;
-template class Pennylane::Algorithms::TensorProdObs<double>;
+template class Pennylane::Simulators::TensorProdObs<float>;
+template class Pennylane::Simulators::TensorProdObs<double>;
-template class Pennylane::Algorithms::Hamiltonian<float>;
-template class Pennylane::Algorithms::Hamiltonian<double>;
+template class Pennylane::Simulators::Hamiltonian<float>;
+template class Pennylane::Simulators::Hamiltonian<double>;
diff --git a/pennylane_lightning/src/algorithms/Observables.hpp b/pennylane_lightning/src/simulator/Observables.hpp
similarity index 99%
rename from pennylane_lightning/src/algorithms/Observables.hpp
rename to pennylane_lightning/src/simulator/Observables.hpp
index bf2e765272..f803276e96 100644
--- a/pennylane_lightning/src/algorithms/Observables.hpp
+++ b/pennylane_lightning/src/simulator/Observables.hpp
@@ -21,7 +21,7 @@
#include <memory>
#include <unordered_set>
-namespace Pennylane::Algorithms {
+namespace Pennylane::Simulators {
/**
* @brief A base class for all observable classes.
@@ -442,4 +442,4 @@ template <typename T> class Hamiltonian final : public Observable<T> {
}
};
-} // namespace Pennylane::Algorithms
+} // namespace Pennylane::Simulators
diff --git a/pennylane_lightning/src/tests/Test_AdjDiff.cpp b/pennylane_lightning/src/tests/Test_AdjDiff.cpp
index a131433ab0..78ffdc5045 100644
--- a/pennylane_lightning/src/tests/Test_AdjDiff.cpp
+++ b/pennylane_lightning/src/tests/Test_AdjDiff.cpp
@@ -23,6 +23,7 @@
using namespace Pennylane;
using namespace Pennylane::Algorithms;
+using namespace Pennylane::Simulators;
TEST_CASE("Algorithms::adjointJacobian Op=RX, Obs=Z", "[Algorithms]") {
const std::vector<double> param{-M_PI / 7, M_PI / 5, 2 * M_PI / 3};
@@ -540,7 +541,7 @@ TEST_CASE(
"Algorithms::adjointJacobian with exceedingly complicated Hamiltonian",
"[Algorithms]") {
using namespace std::literals;
- using Pennylane::Algorithms::detail::HamiltonianApplyInPlace;
+ using Pennylane::Simulators::detail::HamiltonianApplyInPlace;
std::vector<double> param{-M_PI / 7, M_PI / 5, 2 * M_PI / 3};
std::vector<size_t> t_params{0, 2};
diff --git a/pennylane_lightning/src/tests/Test_AlgUtil.cpp b/pennylane_lightning/src/tests/Test_AlgUtil.cpp
index 3698ada7ec..51a1853e6b 100644
--- a/pennylane_lightning/src/tests/Test_AlgUtil.cpp
+++ b/pennylane_lightning/src/tests/Test_AlgUtil.cpp
@@ -5,6 +5,7 @@
using namespace Pennylane;
using namespace Pennylane::Algorithms;
+using namespace Pennylane::Simulators;
class TestException : public std::exception {};
diff --git a/pennylane_lightning/src/tests/Test_Measures.cpp b/pennylane_lightning/src/tests/Test_Measures.cpp
index 311cc714c4..ff6760f7bf 100644
--- a/pennylane_lightning/src/tests/Test_Measures.cpp
+++ b/pennylane_lightning/src/tests/Test_Measures.cpp
@@ -16,6 +16,7 @@
using namespace Pennylane;
using namespace Pennylane::Util;
+using namespace Pennylane::Simulators;
using std::complex;
using std::size_t;
diff --git a/pennylane_lightning/src/tests/Test_Measures_Sparse.cpp b/pennylane_lightning/src/tests/Test_Measures_Sparse.cpp
index 32a2aca8b9..0e361ffde3 100644
--- a/pennylane_lightning/src/tests/Test_Measures_Sparse.cpp
+++ b/pennylane_lightning/src/tests/Test_Measures_Sparse.cpp
@@ -17,6 +17,7 @@
using namespace Pennylane;
using namespace Pennylane::Util;
+using namespace Pennylane::Simulators;
namespace {
using std::complex;
diff --git a/pennylane_lightning/src/tests/Test_Observables.cpp b/pennylane_lightning/src/tests/Test_Observables.cpp
index fb37dba954..c1b62275a9 100644
--- a/pennylane_lightning/src/tests/Test_Observables.cpp
+++ b/pennylane_lightning/src/tests/Test_Observables.cpp
@@ -4,7 +4,7 @@
#include <catch2/catch.hpp>
using namespace Pennylane;
-using namespace Pennylane::Algorithms;
+using namespace Pennylane::Simulators;
using Pennylane::Util::LightningException;
// NOLINTNEXTLINE(readability-function-cognitive-complexity)
diff --git a/pennylane_lightning/src/tests/Test_StateVecAdjDiff.cpp b/pennylane_lightning/src/tests/Test_StateVecAdjDiff.cpp
index 092e0e380b..8b26641cda 100644
--- a/pennylane_lightning/src/tests/Test_StateVecAdjDiff.cpp
+++ b/pennylane_lightning/src/tests/Test_StateVecAdjDiff.cpp
@@ -15,6 +15,7 @@
using namespace Pennylane;
using namespace Pennylane::Util;
using namespace Pennylane::Algorithms;
+using namespace Pennylane::Simulators;
/**
* @brief
diff --git a/tests/test_measures.py b/tests/test_measures.py
index 8df8864b40..4c83c24b4c 100644
--- a/tests/test_measures.py
+++ b/tests/test_measures.py
@@ -227,6 +227,41 @@ def circuit():
assert np.allclose(circuit(), cases[1], atol=tol, rtol=0)
+ @pytest.mark.parametrize(
+ "obs, coeffs, res",
+ [
+ ([qml.PauliX(0) @ qml.PauliZ(1)], [1.0], 0.0),
+ ([qml.PauliZ(0) @ qml.PauliZ(1)], [1.0], math.cos(0.4) * math.cos(-0.2)),
+ (
+ [
+ qml.PauliX(0) @ qml.PauliZ(1),
+ qml.Hermitian(
+ [
+ [1.0, 0.0, 0.0, 0.0],
+ [0.0, 3.0, 0.0, 0.0],
+ [0.0, 0.0, -1.0, 1.0],
+ [0.0, 0.0, 1.0, -2.0],
+ ],
+ wires=[0, 1],
+ ),
+ ],
+ [0.3, 1.0],
+ 0.9319728930156066,
+ ),
+ ],
+ )
+ def test_expval_hamiltonian(self, obs, coeffs, res, tol, dev):
+ """Test expval with Hamiltonian"""
+ ham = qml.Hamiltonian(coeffs, obs)
+
+ @qml.qnode(dev)
+ def circuit():
+ qml.RX(0.4, wires=[0])
+ qml.RY(-0.2, wires=[1])
+ return qml.expval(ham)
+
+ assert np.allclose(circuit(), res, atol=tol, rtol=0)
+
def test_value(self, dev, tol):
"""Test that the expval interface works"""
@@ -428,6 +463,55 @@ def circuit2():
assert np.allclose(circuit1(), circuit2(), atol=tol)
+ @pytest.mark.parametrize(
+ "wires1, wires2",
+ [
+ ([2, 3, 0], [2, 3, 0]),
+ ([0, 1], [0, 1]),
+ ([0, 2, 3], [2, 0, 3]),
+ (["a", "c", "d"], [2, 3, 0]),
+ ([-1, -2, -3], ["q1", "ancilla", 2]),
+ (["a", "c"], [3, 0]),
+ ([-1, -2], ["ancilla", 2]),
+ ],
+ )
+ @pytest.mark.parametrize("C", [np.complex64, np.complex128])
+ def test_wires_expval_hermitian(self, wires1, wires2, C, tol):
+ """Test that the expectation of a circuit is independent from the wire labels used."""
+ dev1 = qml.device("lightning.qubit", wires=wires1, c_dtype=C)
+ dev1._state = dev1._asarray(dev1._state, C)
+
+ dev2 = qml.device("lightning.qubit", wires=wires2)
+ dev2._state = dev2._asarray(dev2._state, C)
+ ob_mat = [
+ [1.0, 2.0, 0.0, 1.0],
+ [2.0, -1.0, 0.0, 0.0],
+ [0.0, 0.0, 2.0, 0.0],
+ [1.0, 0.0, 0.0, -1.0],
+ ]
+
+ n_wires = len(wires1)
+ ob1 = qml.Hermitian(ob_mat, wires=[wires1[0 % n_wires], wires1[1 % n_wires]])
+ ob2 = qml.Hermitian(ob_mat, wires=[wires2[0 % n_wires], wires2[1 % n_wires]])
+
+ @qml.qnode(dev1)
+ def circuit1():
+ qml.RX(0.5, wires=wires1[0 % n_wires])
+ qml.RY(2.0, wires=wires1[1 % n_wires])
+ if n_wires > 1:
+ qml.CNOT(wires=[wires1[0], wires1[1]])
+ return [qml.expval(ob1)]
+
+ @qml.qnode(dev2)
+ def circuit2():
+ qml.RX(0.5, wires=wires2[0 % n_wires])
+ qml.RY(2.0, wires=wires2[1 % n_wires])
+ if n_wires > 1:
+ qml.CNOT(wires=[wires2[0], wires2[1]])
+ return [qml.expval(ob2)]
+
+ assert np.allclose(circuit1(), circuit2(), atol=tol)
+
class TestSample:
"""Tests that samples are properly calculated."""