From b2e5e1da5cac1503ffd99e6a3914c346f5ee9858 Mon Sep 17 00:00:00 2001
From: Sachin Pisal <spisal@nvidia.com>
Date: Tue, 14 Jan 2025 17:56:42 -0800
Subject: [PATCH] Adding evolution API

Signed-off-by: Sachin Pisal <spisal@nvidia.com>
---
 runtime/cudaq/evolution.h | 46 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 runtime/cudaq/evolution.h

diff --git a/runtime/cudaq/evolution.h b/runtime/cudaq/evolution.h
new file mode 100644
index 00000000000..3b86c448ceb
--- /dev/null
+++ b/runtime/cudaq/evolution.h
@@ -0,0 +1,46 @@
+/****************************************************************-*- C++ -*-****
+ * Copyright (c) 2022 - 2025 NVIDIA Corporation & Affiliates.                  *
+ * All rights reserved.                                                        *
+ *                                                                             *
+ * This source code and the accompanying materials are made available under    *
+ * the terms of the Apache License 2.0 which accompanies this distribution.    *
+ ******************************************************************************/
+
+#pragma once
+
+#include "cudaq/operators.h"
+#include "cudaq/schedule.h"
+#include "cudaq/base_integrator.h"
+#include "common/EvolveResult.h"
+
+#include <Eigen/Dense>
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace cudaq {
+class Evolution {
+public:
+    /// Computes the Taylor series expansion of the matrix exponential.
+    static Eigen::MatrixXcd taylor_series_expm(const Eigen::MatrixXcd &op_matrix, int order = 20);
+
+    /// Computes the evolution step matrix
+    static Eigen::MatrixXcd compute_step_matrix(const operator_sum &hamiltonian, const std::map<int, int> &dimensions, const std::map<std::string, std::complex<double>> &parameters, double dt, bool use_gpu = false);
+
+    /// Adds noise channels based on collapse operators.
+    static void add_noise_channel_for_step(const std::string &step_kernel_name, cudaq::noise_model &noise_model, const std::vector<operator_sum> &collapse_operators, const std::map<int, int> &dimensions, const std::map<std::string, std::complex<double>> &parameters, double dt);
+
+    /// Launches an analog Hamiltonian kernel for quantum simulations.
+    static evolve_result launch_analog_hamiltonian_kernel(const std::string &target_name, const operator_sum &hamiltonian, const std::shared_ptr<Schedule> &schedule, int shots_count, bool is_async = false);
+
+    /// Generates evolution kernels for the simulation.
+    static std::vector<std::string> evolution_kernel(int num_qubits, const std::function<Eigen::MatrixXcd(const std::map<std::string, std::complex<double>> &, double)> &compute_step_matrix, const std::vector<double> tlist, const std::vector<std::map<std::string, std::complex<double>>> &schedule_parameters);
+
+    /// Evolves a single quantum state under a given hamiltonian.
+    static evolve_result evolve_single(const operator_sum &hamiltonian, const std::map<int, int> &dimensions, const std::shared_ptr<Schedule> &schedule, state initial_state, const std::vector<operator_sum> &collapse_operators = {}, const std::vector<operator_sum> &observables = {}, bool store_intermediate_results = false, std::shared_ptr<BaseIntegrator<state>> integrator = nullptr, std::optional<int> shots_count = std::nullopt);
+
+    /// Evolves a single or multiple quantum states under a given hamiltonian.
+    static std::vector<evolve_result> evolve(const operator_sum &hamiltonian, const std::map<int, int> &dimensions, const std::shared_ptr<Schedule> &schedule, const std::vector<state> &initial_states, const std::vector<operator_sum> &collapse_operators = {}, const std::vector<operator_sum> &observables = {}, bool store_intermediate_results = false, std::shared_ptr<BaseIntegrator<state>> integrator = nullptr, std::optional<int> shots_count = std::nullopt);
+};
+}
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