C++ operator and matrix API changes

.github/workflows/python_wheels.yml

@@ -250,7 +250,7 @@ jobs:
               echo "::error file=python_wheel.yml::Python tests failed with status $pytest_status."
               exit 1
             fi
-            python${{ inputs.python_version }} -m pip install --user fastapi uvicorn llvmlite 
+            python${{ inputs.python_version }} -m pip install --user fastapi uvicorn llvmlite openfermionpyscf==0.5
             for backendTest in /tmp/tests/backends/*.py; do 
               python${{ inputs.python_version }} -m pytest $backendTest
               pytest_status=$?

Overview.md

@@ -116,10 +116,8 @@ diagnostics infrastructures for free.
 
 Specifically, this library provides the `qudit`, `qubit`, `qreg`, and `qspan`
 types, the intrinsic quantum operations, and the algorithmic primitives like
-`cudaq::sample` and `cudaq::observe`.
-
-This library defines the `cudaq::spin_op` for defining general Pauli tensor
-product terms.
+`cudaq::sample`, `cudaq::observe`, and `cudaq::evolve`, as well as their
+asynchronous versions.
 
 This library defines the `quantum_platform` architecture, enabling CUDA-Q to
 target both simulated and physical quantum computing architectures.

docs/sphinx/specification/cudaq/operations.rst

@@ -96,7 +96,7 @@ The default set of quantum intrinsic operations for the cudaq::qubit type is as
 
       bool MEASURE_OP(qubit &q) noexcept;
       std::vector<bool> MEASURE_OP(qvector &q) noexcept;
-      double measure(cudaq::spin_op & term) noexcept { ... }
+      double measure(const cudaq::spin_op & term) noexcept { ... }
   }
 
 **[1]** For the default implementation of the :code:`cudaq::qubit` intrinsic operations, we let 

lib/Optimizer/Transforms/ObserveAnsatz.cpp

@@ -225,11 +225,16 @@ struct AppendMeasurements : public OpRewritePattern<func::FuncOp> {
       return funcOp.emitOpError("Errors encountered in pass analysis");
     auto nQubits = iter->second.nQubits;
 
-    if (nQubits != termBSF.size() / 2)
+    if (nQubits < termBSF.size() / 2)
       return funcOp.emitOpError("Invalid number of binary-symplectic elements "
-                                "provided. Must provide 2 * NQubits = " +
+                                "provided: " +
+                                std::to_string(termBSF.size()) +
+                                ". Must provide at most 2 * NQubits = " +
                                 std::to_string(2 * nQubits));
 
+    // Update nQubits so we only measure the requested qubits.
+    nQubits = termBSF.size() / 2;
+
     // If the mapping pass was not run, we expect no pre-existing measurements.
     if (!iter->second.mappingPassRan && !iter->second.measurements.empty())
       return funcOp.emitOpError("Cannot observe kernel with measures in it.");

python/cudaq/operator/definitions.py

@@ -194,6 +194,14 @@ def __init__(self):
         # This should never be called. We have `__new__` method instead.
         raise ValueError("Not supported")
 
+    @staticmethod
+    def empty() -> OperatorSum:
+        return OperatorSum()
+
+    @staticmethod
+    def identity() -> OperatorSum:
+        return ProductOperator(ScalarOperator.const(1.))
+
     # Convert from a Pauli word to an Operator
     @staticmethod
     def from_word(word: str) -> ProductOperator:

python/cudaq/operator/expressions.py

@@ -38,8 +38,6 @@ def __init__(self: OperatorSum,
                 evaluating the operator expression.
         """
         self._terms = tuple(terms)
-        if len(self._terms) == 0:
-            self._terms = (ProductOperator((ScalarOperator.const(0),)),)
         self._cache = {}
         self._iter_idx = 0
 
@@ -168,6 +166,8 @@ def padded_term(term: ProductOperator) -> ProductOperator:
                     term *= ElementaryOperator.identity(degree)
             return term
 
+        if len(self._terms) == 0:
+            return arithmetics.evaluate(ScalarOperator.const(0))
         if pad_terms:
             sum = padded_term(self._terms[0])._evaluate(arithmetics, pad_terms)
             for term in self._terms[1:]:
@@ -345,6 +345,7 @@ def to_sparse_matrix(self: OperatorSum):
         return self._to_spinop().to_sparse_matrix()
 
     def __iter__(self: OperatorSum) -> OperatorSum:
+        self._iter_idx = 0
         return self
 
     def __next__(self: OperatorSum) -> ProductOperator:

python/runtime/cudaq/spin/py_matrix.cpp

@@ -10,8 +10,8 @@
 #include <pybind11/operators.h>
 #include <pybind11/stl.h>
 
-#include "cudaq/spin_op.h"
-#include "py_spin_op.h"
+#include "cudaq/utils/matrix.h"
+#include "py_matrix.h"
 
 #include <complex>
 
@@ -39,7 +39,7 @@ void bindComplexMatrix(py::module &mod) {
       /// The following makes this fully compatible with NumPy
       .def_buffer([](complex_matrix &op) -> py::buffer_info {
         return py::buffer_info(
-            op.data(), sizeof(std::complex<double>),
+            op.data, sizeof(std::complex<double>),
             py::format_descriptor<std::complex<double>>::format(), 2,
             {op.rows(), op.cols()},
             {sizeof(std::complex<double>) * op.cols(),
@@ -48,7 +48,7 @@ void bindComplexMatrix(py::module &mod) {
       .def(py::init([](const py::buffer &b) {
              py::buffer_info info = b.request();
              complex_matrix m(info.shape[0], info.shape[1]);
-             extractMatrixData(info, m.data());
+             extractMatrixData(info, m.data);
              return m;
            }),
            "Create a :class:`ComplexMatrix` from a buffer of data, such as a "
@@ -91,7 +91,7 @@ void bindComplexMatrix(py::module &mod) {
                 static_cast<ssize_t>(sizeof(std::complex<double>))};
 
             // Return a numpy array without copying data
-            return py::array_t<std::complex<double>>(shape, strides, m.data());
+            return py::array_t<std::complex<double>>(shape, strides, m.data);
           },
           "Convert :class:`ComplexMatrix` to numpy.ndarray.");
 }

python/tests/backends/test_Quantinuum_LocalEmulation_kernel.py

@@ -14,6 +14,15 @@
 from typing import List
 
 
+def requires_openfermion():
+    open_fermion_found = True
+    try:
+        import openfermion, openfermionpyscf
+    except:
+        open_fermion_found = False
+    return pytest.mark.skipif(not open_fermion_found,
+        reason=f"openfermion is not installed")
+
 def assert_close(want, got, tolerance=1.0e-1) -> bool:
     return abs(want - got) < tolerance
 
@@ -320,6 +329,23 @@ def test_toffoli():
         cudaq.sample(test_toffoli)
 
 
+@requires_openfermion()
+def test_observe_chemistry():
+    geometry = [('H', (0., 0., 0.)), ('H', (0., 0., .7474))]
+    molecule, data = cudaq.chemistry.create_molecular_hamiltonian(geometry, 'sto-3g', 1, 0)
+
+    qubit_count = data.n_orbitals * 2
+
+    @cudaq.kernel
+    def kernel(thetas: list[float]):
+        qubits = cudaq.qvector(qubit_count)
+
+    result = cudaq.observe(kernel, molecule, [.0,.0,.0,.0], shots_count = 1000)
+
+    expectation = result.expectation()
+    assert_close(expectation, 0.707)
+
+
 # leave for gdb debugging
 if __name__ == "__main__":
     loc = os.path.abspath(__file__)

python/tests/builder/test_kernel_builder.py

@@ -12,7 +12,7 @@
 import pytest
 import random
 import numpy as np
-import sys
+import os
 from typing import List
 
 import cudaq

runtime/common/Trace.h

@@ -14,6 +14,8 @@
 
 namespace cudaq {
 
+struct QuditInfo;
+
 /// @brief A trace is a circuit representation of the executed computation, as
 /// seen by the execution manager. (Here, a circuit is represented as a list
 /// of instructions on qudits). Since the execution manager cannot "see" control

runtime/cudaq/CMakeLists.txt

@@ -23,7 +23,7 @@ add_library(${LIBRARY_NAME}
                 qis/remote_state.cpp
                 qis/state.cpp
                 utils/cudaq_utils.cpp
-                utils/tensor.cpp
+                utils/matrix.cpp
                 distributed/mpi_plugin.cpp)
 
 set_property(GLOBAL APPEND PROPERTY CUDAQ_RUNTIME_LIBS ${LIBRARY_NAME})

runtime/cudaq/algorithms/evolve.h

@@ -27,50 +27,49 @@ using async_evolve_result = std::future<evolve_result>;
 
 namespace __internal__ {
 template <typename OpTy>
-cudaq::operator_sum<cudaq::matrix_operator> convertOp(const OpTy &op) {
+cudaq::sum_op<cudaq::matrix_handler> convertOp(const OpTy &op) {
   if constexpr (std::is_convertible_v<
-                    OpTy, cudaq::product_operator<cudaq::matrix_operator>>) {
-    cudaq::operator_sum<cudaq::matrix_operator> convertedOp(op);
+                    OpTy, cudaq::product_op<cudaq::matrix_handler>>) {
+    cudaq::sum_op<cudaq::matrix_handler> convertedOp(op);
     return convertedOp;
   } else if constexpr (std::is_convertible_v<
-                           OpTy, cudaq::operator_sum<cudaq::matrix_operator>>) {
+                           OpTy, cudaq::sum_op<cudaq::matrix_handler>>) {
     return op;
   } else {
     throw std::invalid_argument("Invalid operator type: cannot convert type " +
                                 std::string(typeid(op).name()) +
-                                " to cudaq::product_operator or "
-                                "cudaq::operator_sum");
+                                " to cudaq::product_op or "
+                                "cudaq::sum_op");
   }
 }
 
 template <typename OpTy>
-std::vector<cudaq::operator_sum<cudaq::matrix_operator>>
+std::vector<cudaq::sum_op<cudaq::matrix_handler>>
 convertOps(const std::vector<OpTy> &ops) {
-  std::vector<cudaq::operator_sum<cudaq::matrix_operator>> converted;
+  std::vector<cudaq::sum_op<cudaq::matrix_handler>> converted;
   for (const auto &op : ops)
     converted.emplace_back(convertOp(op));
   return converted;
 }
 
 template <typename OpTy>
-std::vector<cudaq::operator_sum<cudaq::matrix_operator>>
+std::vector<cudaq::sum_op<cudaq::matrix_handler>>
 convertOps(const std::initializer_list<OpTy> &ops) {
-  std::vector<cudaq::operator_sum<cudaq::matrix_operator>> converted;
+  std::vector<cudaq::sum_op<cudaq::matrix_handler>> converted;
   for (const auto &op : ops)
     converted.emplace_back(convertOp(op));
   return converted;
 }
 } // namespace __internal__
 
 #if CUDAQ_USE_STD20
-template <
-    operator_type HamTy,
-    operator_type CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-    operator_type ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>>
+template <operator_type HamTy,
+          operator_type CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          operator_type ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>>
 #else
 template <typename HamTy,
-          typename CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-          typename ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
+          typename CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          typename ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>,
           typename = std::enable_if_t<cudaq::operator_type<HamTy> &&
                                       cudaq::operator_type<CollapseOpTy> &&
                                       cudaq::operator_type<ObserveOpTy>>>
@@ -127,14 +126,13 @@ evolve_result evolve(const HamTy &hamiltonian,
 }
 
 #if CUDAQ_USE_STD20
-template <
-    operator_type HamTy,
-    operator_type CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-    operator_type ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>>
+template <operator_type HamTy,
+          operator_type CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          operator_type ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>>
 #else
 template <typename HamTy,
-          typename CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-          typename ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
+          typename CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          typename ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>,
           typename = std::enable_if_t<cudaq::operator_type<HamTy> &&
                                       cudaq::operator_type<CollapseOpTy> &&
                                       cudaq::operator_type<ObserveOpTy>>>
@@ -163,14 +161,13 @@ evolve(const HamTy &hamiltonian, const cudaq::dimension_map &dimensions,
 }
 
 #if CUDAQ_USE_STD20
-template <
-    operator_type HamTy,
-    operator_type CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-    operator_type ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>>
+template <operator_type HamTy,
+          operator_type CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          operator_type ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>>
 #else
 template <typename HamTy,
-          typename CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-          typename ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
+          typename CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          typename ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>,
           typename = std::enable_if_t<cudaq::operator_type<HamTy> &&
                                       cudaq::operator_type<CollapseOpTy> &&
                                       cudaq::operator_type<ObserveOpTy>>>
@@ -199,14 +196,13 @@ evolve(const HamTy &hamiltonian, const cudaq::dimension_map &dimensions,
 }
 
 #if CUDAQ_USE_STD20
-template <
-    operator_type HamTy,
-    operator_type CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-    operator_type ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>>
+template <operator_type HamTy,
+          operator_type CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          operator_type ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>>
 #else
 template <typename HamTy,
-          typename CollapseOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
-          typename ObserveOpTy = cudaq::operator_sum<cudaq::matrix_operator>,
+          typename CollapseOpTy = cudaq::sum_op<cudaq::matrix_handler>,
+          typename ObserveOpTy = cudaq::sum_op<cudaq::matrix_handler>,
           typename = std::enable_if_t<cudaq::operator_type<HamTy> &&
                                       cudaq::operator_type<CollapseOpTy> &&
                                       cudaq::operator_type<ObserveOpTy>>>

runtime/cudaq/algorithms/evolve_internal.h

@@ -156,12 +156,11 @@ evolve_async(std::function<evolve_result()> evolveFunctor,
 }
 
 evolve_result evolveSingle(
-    const operator_sum<cudaq::matrix_operator> &hamiltonian,
+    const sum_op<cudaq::matrix_handler> &hamiltonian,
     const cudaq::dimension_map &dimensions, const schedule &schedule,
     const state &initial_state, base_integrator &integrator,
-    const std::vector<operator_sum<cudaq::matrix_operator>>
-        &collapse_operators = {},
-    const std::vector<operator_sum<cudaq::matrix_operator>> &observables = {},
+    const std::vector<sum_op<cudaq::matrix_handler>> &collapse_operators = {},
+    const std::vector<sum_op<cudaq::matrix_handler>> &observables = {},
     bool store_intermediate_results = false,
     std::optional<int> shots_count = std::nullopt);
 

runtime/cudaq/base_integrator.h

@@ -18,21 +18,19 @@ namespace cudaq {
 // Struct captures the system dynamics needed by the integrator
 struct SystemDynamics {
   std::vector<int64_t> modeExtents;
-  operator_sum<cudaq::matrix_operator> hamiltonian;
-  std::vector<operator_sum<cudaq::matrix_operator>> collapseOps;
+  sum_op<cudaq::matrix_handler> hamiltonian;
+  std::vector<sum_op<cudaq::matrix_handler>> collapseOps;
   std::unordered_map<std::string, std::complex<double>> parameters;
 
   SystemDynamics(
       const std::vector<int64_t> extents,
-      const operator_sum<cudaq::matrix_operator> &ham,
-      const std::vector<operator_sum<cudaq::matrix_operator>> &cOps = {},
+      const sum_op<cudaq::matrix_handler> &ham,
+      const std::vector<sum_op<cudaq::matrix_handler>> &cOps = {},
       const std::unordered_map<std::string, std::complex<double>> &params = {})
       : modeExtents(extents), hamiltonian(ham), collapseOps(cOps),
         parameters(params) {}
 
-  SystemDynamics()
-      : hamiltonian(operator_sum<cudaq::matrix_operator>(
-            cudaq::matrix_operator::empty())){};
+  SystemDynamics() : hamiltonian(cudaq::matrix_op::empty()){};
 };
 
 class base_time_stepper;