| Line | Branch | Decision | Exec | Source |
|---|---|---|---|---|
| 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 | ||||
| 17 | #include "Circuit/Circuit.hpp" | |||
| 18 | #include "Utils/Json.hpp" | |||
| 19 | #include "Utils/PauliStrings.hpp" | |||
| 20 | ||||
| 21 | namespace tket { | |||
| 22 | ||||
| 23 | /** | |||
| 24 | * MeasurementSetup | |||
| 25 | * Captures an expectation value experiment. | |||
| 26 | * Given a collection of Pauli terms, the setup contains a collection | |||
| 27 | * of measurement circuits from which each Pauli measurement can be extracted. | |||
| 28 | * | |||
| 29 | * The result_map maps Pauli terms to circuits from which the expectation value | |||
| 30 | * can be obtained, along with the classical post-processing required on each | |||
| 31 | * shot (which bits/columns of the shot table to XOR together, and whether to | |||
| 32 | * invert the final value). | |||
| 33 | * | |||
| 34 | * There may be multiple measurement circuits that measure the same Pauli term, | |||
| 35 | * so we have a vector of MeasurementBitMaps for each term to exploit this and | |||
| 36 | * effectively get extra shots for free. | |||
| 37 | */ | |||
| 38 | class MeasurementSetup { | |||
| 39 | public: | |||
| 40 | struct MeasurementBitMap { | |||
| 41 | ✗ | MeasurementBitMap() : circ_index{0}, invert{false} {} | ||
| 42 | ✗ | MeasurementBitMap( | ||
| 43 | unsigned _circ_index, const std::vector<unsigned> &_bits, | |||
| 44 | bool _invert = 0) | |||
| 45 | ✗ | : circ_index{_circ_index}, bits{_bits}, invert{_invert} {} | ||
| 46 | ||||
| 47 | unsigned circ_index; | |||
| 48 | std::vector<unsigned> bits; | |||
| 49 | bool invert; | |||
| 50 | ||||
| 51 | 18 | const unsigned &get_circ_index() const { return circ_index; } | ||
| 52 | 18 | const std::vector<unsigned> &get_bits() const { return bits; } | ||
| 53 | 18 | const bool &get_invert() const { return invert; } | ||
| 54 | ||||
| 55 | std::string to_str() const; | |||
| 56 | }; | |||
| 57 | struct QPSHasher { | |||
| 58 | 177 | std::size_t operator()(const QubitPauliString &qps) const { | ||
| 59 | 177 | return hash_value(qps); | ||
| 60 | } | |||
| 61 | }; | |||
| 62 | typedef std::unordered_map< | |||
| 63 | QubitPauliString, std::vector<MeasurementBitMap>, QPSHasher> | |||
| 64 | measure_result_map_t; | |||
| 65 | ||||
| 66 | ✗ | const std::vector<Circuit> &get_circs() const { return measurement_circs; } | ||
| 67 | 4 | const measure_result_map_t &get_result_map() const { return result_map; } | ||
| 68 | ||||
| 69 | void add_measurement_circuit(const Circuit &circ); | |||
| 70 | void add_result_for_term( | |||
| 71 | const QubitPauliString &term, const MeasurementBitMap &result); | |||
| 72 | /** | |||
| 73 | * Rejects the coefficient in the QubitPauliTensor. Used for | |||
| 74 | * convenience at the C++ level, and should not be exposed. | |||
| 75 | */ | |||
| 76 | void add_result_for_term( | |||
| 77 | const QubitPauliTensor &term, const MeasurementBitMap &result); | |||
| 78 | /** | |||
| 79 | * Checks that the tensors to be measured correspond to the | |||
| 80 | * correct tensors generated by the measurement circs. Includes | |||
| 81 | * parity checks. | |||
| 82 | */ | |||
| 83 | bool verify() const; | |||
| 84 | ||||
| 85 | std::string to_str() const; | |||
| 86 | ||||
| 87 | private: | |||
| 88 | /** | |||
| 89 | * Clifford circuits to generate the correct Pauli measurements, | |||
| 90 | * with Measure gates on the required qubits. | |||
| 91 | */ | |||
| 92 | std::vector<Circuit> measurement_circs; | |||
| 93 | measure_result_map_t result_map; | |||
| 94 | }; | |||
| 95 | ||||
| 96 | JSON_DECL(MeasurementSetup::MeasurementBitMap) | |||
| 97 | JSON_DECL(MeasurementSetup) | |||
| 98 | ||||
| 99 | } // namespace tket | |||
| 100 |