Postselection

Functions

template<typename BitstringVectorType, typename WeightVectorType, typename CallableType>
std::pair<BitstringVectorType, WeightVectorType> Qiskit::addon::sqd::postselect_bitstrings(const BitstringVectorType &bitstrings, const WeightVectorType &weights, CallableType filter_function)

Post-select bitstrings based on a given criteria.

Example

std::vector<std::bitset<6>> bitstrings = {0b011010, 0b100011};
std::vector<double> weights = {0.1, 0.7};
auto [new_bitstrings, new_weights] = Qiskit::addon::sqd::postselect_bitstrings(
    bitstrings, weights, Qiskit::addon::sqd::MatchesRightLeftHamming(1, 2)
);
Parameters:

  • bitstrings – [in] Bitstrings to consider.

  • weights – [in] Relative weight of each bitstring (need not be normalized to 1).

  • filter_function – [in] Callable which returns a boolean indicating whether a is to be kept.

Template Parameters:

  • BitstringVectorType – Type of bitstrings, compatible with std::vector<boost::dynamic_bitset<>>.

  • WeightVectorType – Type of weights, compatible with std::vector<double>.

  • CallableType – Type of filter_function, compatible with bool (*f)(const BitstringType &).

Returns:

Post-selected bitstrings and their corresponding weights, normalized to 1.

Classes

template<typename UnsignedType = uint32_t>
class MatchesRightLeftHamming

Functor which returns true if a bitstring has a predetermined Hamming weight.

Public Functions

inline explicit MatchesRightLeftHamming(UnsignedType right_target, UnsignedType left_target)

Constructor.

template<typename BitstringType>
inline bool operator()(const BitstringType &bitstring) const

Function to be used as filter.

Parameters:

bitstring – [in] Bitstring to consider.

Template Parameters:

BitstringType – Type of bitstring, compatible with boost::dynamic_bitset<> (for example).

Returns:

true if the bitstring matches the Hamming weight that the functor was initialized with.