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|---|---|---|---|---|
| 1 | // Copyright 2019-2022 Cambridge Quantum Computing | |||
| 2 | // | |||
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); | |||
| 4 | // you may not use this file except in compliance with the License. | |||
| 5 | // You may obtain a copy of the License at | |||
| 6 | // | |||
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 | |||
| 8 | // | |||
| 9 | // Unless required by applicable law or agreed to in writing, software | |||
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, | |||
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |||
| 12 | // See the License for the specific language governing permissions and | |||
| 13 | // limitations under the License. | |||
| 14 | ||||
| 15 | #pragma once | |||
| 16 | #include "Converters/Gauss.hpp" | |||
| 17 | #include "Path.hpp" | |||
| 18 | ||||
| 19 | namespace tket { | |||
| 20 | namespace aas { | |||
| 21 | ||||
| 22 | typedef std::pair<unsigned, unsigned> Operation; | |||
| 23 | typedef std::list<Operation> OperationList; | |||
| 24 | ||||
| 25 | enum class CNotSynthType { SWAP, HamPath, Rec }; | |||
| 26 | ||||
| 27 | /** | |||
| 28 | * Nodes in a Steiner tree may correspond to different values in the biadjacency | |||
| 29 | * action matrix or phase polynomial | |||
| 30 | */ | |||
| 31 | enum class SteinerNodeType { | |||
| 32 | // "in tree" := not a leaf & not disconnected from tree | |||
| 33 | ZeroInTree, | |||
| 34 | OneInTree, | |||
| 35 | // all leaves are 1s by definition | |||
| 36 | Leaf, | |||
| 37 | OutOfTree | |||
| 38 | }; | |||
| 39 | ||||
| 40 | class InvalidCostCalculation : public std::logic_error { | |||
| 41 | public: | |||
| 42 | ✗ | explicit InvalidCostCalculation(const std::string &message) | ||
| 43 | ✗ | : std::logic_error(message) {} | ||
| 44 | }; | |||
| 45 | ||||
| 46 | class InvalidRowOperation : public std::logic_error { | |||
| 47 | public: | |||
| 48 | ✗ | explicit InvalidRowOperation(const std::string &message) | ||
| 49 | ✗ | : std::logic_error(message) {} | ||
| 50 | }; | |||
| 51 | ||||
| 52 | /** | |||
| 53 | * This clas is creating a steiner tree, which is a mst including all the nodes | |||
| 54 | * of a given phase gadget plus all the nodes which are neede to connect all the | |||
| 55 | * nodes of the gadget. This class also offers the function to reduce this tree | |||
| 56 | * by extracting operations steps by step. This class is designed with | |||
| 57 | * architecture aware synthesis in mind; it may not be suitable for other | |||
| 58 | * generic purposes. | |||
| 59 | */ | |||
| 60 | class SteinerTree { | |||
| 61 | public: | |||
| 62 | SteinerTree() {} | |||
| 63 | /** | |||
| 64 | * Construct a Steinertree from given parameters | |||
| 65 | * @param pathhandler giving the included edges | |||
| 66 | * @param nodes_to_add list by ref, will be changed during the construction of | |||
| 67 | * the tree | |||
| 68 | * @param root_node initial node, deleted in the last step | |||
| 69 | */ | |||
| 70 | explicit SteinerTree( | |||
| 71 | const PathHandler &pathhandler, std::list<unsigned> &nodes_to_add, | |||
| 72 | unsigned root_node); // N.B. non-const list by ref! | |||
| 73 | ||||
| 74 | /** | |||
| 75 | * calculate cost of performing a CNOT between two neighbouring nodes, | |||
| 76 | * dependent on the SteinerNodeTypes. | |||
| 77 | * @param i control index of operation | |||
| 78 | * @param j target index of operation | |||
| 79 | */ | |||
| 80 | int cost_of_operation(unsigned i, unsigned j) const; | |||
| 81 | ||||
| 82 | /** | |||
| 83 | * initialises the tree | |||
| 84 | * @param pathhandler connectivity for the construction | |||
| 85 | * @param nodes_to_add list of nodes which should be added, the list will be | |||
| 86 | * changes during the process | |||
| 87 | * | |||
| 88 | */ | |||
| 89 | void init_tree( | |||
| 90 | const PathHandler &pathhandler, std::list<unsigned> &nodes_to_add); | |||
| 91 | ||||
| 92 | /** | |||
| 93 | * adds the closesd nodes to a given list to the tree | |||
| 94 | * @param pathhandler connectivity for the construction | |||
| 95 | * @param nodes_to_add list of nodes which should be added, the list will be | |||
| 96 | */ | |||
| 97 | void add_closest_node_to_tree( | |||
| 98 | const PathHandler &pathhandler, std::list<unsigned> &nodes_to_add); | |||
| 99 | ||||
| 100 | /** | |||
| 101 | * adds a list of nodes to a given list to the tree | |||
| 102 | * @param pathhandler connectivity for the construction | |||
| 103 | * @param node_in_tree node in tree which is closest to the node to add | |||
| 104 | * @param node_to_add node which should be added | |||
| 105 | */ | |||
| 106 | void add_path_to_tree( | |||
| 107 | const PathHandler &pathhandler, unsigned node_in_tree, | |||
| 108 | unsigned node_to_add); | |||
| 109 | ||||
| 110 | /** | |||
| 111 | * calculates the available operation in this tree which could be executed | |||
| 112 | * @param pathhandler conections used for the calculation | |||
| 113 | * @return gives the list of all avilable operations | |||
| 114 | */ | |||
| 115 | OperationList operations_available(const PathHandler &pathhandler) const; | |||
| 116 | ||||
| 117 | /** | |||
| 118 | * Implements a CNOT from node j to node i, updates costs and tree | |||
| 119 | * @param i control index | |||
| 120 | * @param j target index | |||
| 121 | */ | |||
| 122 | void add_row(unsigned i, unsigned j); | |||
| 123 | ||||
| 124 | /** | |||
| 125 | * checks is the tree is fully reduced | |||
| 126 | * @return true if fully reduced | |||
| 127 | */ | |||
| 128 | bool fully_reduced() const; | |||
| 129 | ||||
| 130 | /** | |||
| 131 | * gives the cost of the tree | |||
| 132 | * @return cost of the tree | |||
| 133 | */ | |||
| 134 | unsigned calculate_cost() const; | |||
| 135 | ||||
| 136 | /** | |||
| 137 | * returns the nodes of the tree which has the highest index. only the out of | |||
| 138 | * tree nodes are not taken into consideration | |||
| 139 | * @return index of maximum node | |||
| 140 | */ | |||
| 141 | unsigned get_max_element() const; | |||
| 142 | ||||
| 143 | /** | |||
| 144 | * gives all nodes of the tree which are leaf, one in or zero in | |||
| 145 | * @return ordered list of all nodes | |||
| 146 | */ | |||
| 147 | std::vector<unsigned> nodes() const; | |||
| 148 | ||||
| 149 | unsigned tree_cost; // the cost to reduce the Steiner tree alone | |||
| 150 | int last_operation_cost; | |||
| 151 | unsigned root; | |||
| 152 | std::vector<SteinerNodeType> node_types; | |||
| 153 | std::vector<unsigned> num_neighbours; | |||
| 154 | std::list<unsigned> tree_nodes; | |||
| 155 | }; | |||
| 156 | ||||
| 157 | /** | |||
| 158 | * object to store and perform the swap nased cnot synthesis | |||
| 159 | */ | |||
| 160 | class CNotSwapSynth { | |||
| 161 | public: | |||
| 162 | CNotSwapSynth() {} | |||
| 163 | /** | |||
| 164 | * construct the object for the cnot swap synth and perform the reduction | |||
| 165 | * @param pathhandler path for reduction | |||
| 166 | * @param CNOT_mat input of executed cnots which should be reduced | |||
| 167 | */ | |||
| 168 | explicit CNotSwapSynth( | |||
| 169 | const PathHandler &pathhandler, const DiagMatrix &CNOT_mat); | |||
| 170 | ||||
| 171 | /** | |||
| 172 | * gives the calculated circuit | |||
| 173 | */ | |||
| 174 | Circuit get_circuit(); | |||
| 175 | ||||
| 176 | /** | |||
| 177 | * checks if the matrix is id after reduction | |||
| 178 | * @return true if matrix is id | |||
| 179 | */ | |||
| 180 | bool valid_result(); | |||
| 181 | ||||
| 182 | private: | |||
| 183 | void add_swap(unsigned first, unsigned second); | |||
| 184 | void cleanup_swaps(); | |||
| 185 | unsigned swap_to_root(unsigned start_node, unsigned current_row); | |||
| 186 | ||||
| 187 | PathHandler paths; | |||
| 188 | DiagMatrix CNOT_matrix; | |||
| 189 | Circuit circ; | |||
| 190 | std::stack<std::pair<unsigned, unsigned>> swaps; | |||
| 191 | }; | |||
| 192 | ||||
| 193 | /** | |||
| 194 | * This method uses Kissinger & de Meijer's Steiner-Gauss | |||
| 195 | * (https://arxiv.org/abs/1904.00633), and reduces the CNOT_matrix, which is | |||
| 196 | * non-const. This function offers the recursive algorithm and the Hamilton | |||
| 197 | * based algorithm | |||
| 198 | * @param CNOT_matrix input of executed cnots which should be reduced | |||
| 199 | * @param paths pathhandler used for the reduction | |||
| 200 | * @param cnottype type of algorithm which could be CNotSynthType::Rec or | |||
| 201 | * CNotSynthType::HamPath | |||
| 202 | * @return routed circuit | |||
| 203 | */ | |||
| 204 | Circuit aas_CNOT_synth( | |||
| 205 | DiagMatrix &CNOT_matrix, const PathHandler &paths, | |||
| 206 | CNotSynthType cnottype = CNotSynthType::Rec); | |||
| 207 | ||||
| 208 | /** | |||
| 209 | * this method offers the swap bases cnot synth | |||
| 210 | * @param CNOT_matrix input of executed cnots which should be reduced | |||
| 211 | * @param paths pathhandler used for the reduction | |||
| 212 | * @return routed circuit | |||
| 213 | */ | |||
| 214 | Circuit aas_CNOT_synth_SWAP(DiagMatrix &CNOT_matrix, const PathHandler &paths); | |||
| 215 | ||||
| 216 | } // namespace aas | |||
| 217 | } // namespace tket | |||
| 218 |