Template Class MeasurementsBase¶
Defined in File MeasurementsBase.hpp
Class Documentation¶
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template<class StateVectorT, class Derived>
class MeasurementsBase¶ Observable’s Measurement Class.
This class performs measurements in the state vector provided to its constructor. Observables are defined by its operator(matrix), the observable class, or through a string-based function dispatch.
- Template Parameters
StateVectorT –
Derived –
Public Functions
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inline explicit MeasurementsBase(const StateVectorT &statevector)¶
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inline void setSeed(const size_t seed)¶
Set the seed of the internal random generator.
- Parameters
seed – Seed
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inline void setRandomSeed()¶
Randomly set the seed of the internal random generator.
- Parameters
seed – Seed
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inline auto expval(const Observable<StateVectorT> &obs) -> PrecisionT¶
Calculate the expectation value for a general Observable.
- Parameters
obs – Observable.
- Returns
Expectation value with respect to the given observable.
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inline auto var(const Observable<StateVectorT> &obs) -> PrecisionT¶
Calculate the variance for a general Observable.
- Parameters
obs – Observable.
- Returns
Variance with respect to the given observable.
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inline auto probs() -> std::vector<PrecisionT>¶
Probabilities of each computational basis state.
- Returns
Floating point std::vector with probabilities in lexicographic order.
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inline auto probs(const std::vector<size_t> &wires) -> std::vector<PrecisionT>¶
Probabilities for a subset of the full system.
- Parameters
wires – Wires will restrict probabilities to a subset of the full system.
- Returns
Floating point std::vector with probabilities. The basis columns are rearranged according to wires.
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inline auto generate_samples(size_t num_samples) -> std::vector<size_t>¶
Generate samples.
- Parameters
num_samples – Number of samples
- Returns
1-D vector of samples in binary with each sample separated by a stride equal to the number of qubits.
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inline auto expval(const Observable<StateVectorT> &obs, const size_t &num_shots, const std::vector<size_t> &shot_range = {}) -> PrecisionT¶
Calculate the expectation value for a general Observable.
- Parameters
obs – Observable.
num_shots – Number of shots used to generate samples
shot_range – The range of samples to use. All samples are used by default.
- Returns
Expectation value with respect to the given observable.
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inline auto measure_with_samples(const Observable<StateVectorT> &obs, const size_t &num_shots, const std::vector<size_t> &shot_range) -> std::vector<PrecisionT>¶
Calculate the expectation value for a general Observable.
- Parameters
obs – Observable.
num_shots – Number of shots used to generate samples
shot_range – The range of samples to use. All samples are used by default.
- Returns
Expectation value with respect to the given observable.
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inline auto var(const Observable<StateVectorT> &obs, const size_t &num_shots) -> PrecisionT¶
Calculate the variance for an observable with the number of shots.
- Parameters
obs – An observable object.
num_shots – Number of shots used to generate samples
- Returns
Variance of the given observable.
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inline auto probs(const Observable<StateVectorT> &obs, size_t num_shots = 0) -> std::vector<PrecisionT>¶
Probabilities to measure rotated basis states.
- Parameters
obs – An observable object.
num_shots – Number of shots (Optional). If specified with a non-zero number, shot-noise will be added to return probabilities
- Returns
Floating point std::vector with probabilities. The basis columns are rearranged according to wires.
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inline auto probs(const std::vector<size_t> &wires, size_t num_shots) -> std::vector<PrecisionT>¶
Probabilities with shot-noise for a subset of the full system.
- Parameters
wires – Wires will restrict probabilities to a subset of the full system.
num_shots – Number of shots.
- Returns
Floating point std::vector with probabilities.
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inline auto probs(size_t num_shots) -> std::vector<PrecisionT>¶
Probabilities with shot-noise.
- Parameters
num_shots – Number of shots.
- Returns
Floating point std::vector with probabilities.
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inline auto sample(const Observable<StateVectorT> &obs, const size_t &num_shots) -> std::vector<PrecisionT>¶
Return samples drawn from eigenvalues of the observable.
- Parameters
obs – The observable object to sample
num_shots – Number of shots used to generate samples
- Returns
Samples of eigenvalues of the observable
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inline auto sample(const size_t &num_shots) -> std::vector<size_t>¶
Return the raw basis state samples.
- Parameters
num_shots – Number of shots used to generate samples
- Returns
Raw basis state samples
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inline auto counts(const Observable<StateVectorT> &obs, const size_t &num_shots) -> std::unordered_map<PrecisionT, size_t>¶
Groups the eigenvalues of samples into a dictionary showing number of occurences for each possible outcome with the number of shots.
- Parameters
obs – The observable to sample
num_shots – Number of wires the sampled observable was performed on
- Returns
std::unordered_map<PrecisionT, size_t> with format
{'EigenValue': num_occurences}
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inline auto counts(const size_t &num_shots) -> std::unordered_map<size_t, size_t>¶
Groups the samples into a dictionary showing number of occurences for each possible outcome with the number of shots.
- Parameters
num_shots – Number of wires the sampled observable was performed on
- Returns
std::unordered_map<size_t, size_t> with format
{'outcome': num_occurences}