Stabilizer simulator

class StabilizerSimulator

Stabilizer simulator class.

Simulator class implemented using the stabilizer formalism.

Public Functions

StabilizerSimulator(unsigned num_qubits, unsigned seed)

Constructor.

Parameters

  • num_qubits: Maximum number of allocated qubits

  • seed: Seed for pseudo-random number generator

void allocate_qubit(unsigned qubit_id)

Allocate one qubit with a given id.

Parameters

  • qubit_id: ID of the qubit to allocate

Exceptions

  • std::runtime_error: if the qubit de-allocation fails either due to the qubit being already allocated or if the maximum number of allocated qubit has been reached.

void allocate_all_qubits()

Convenience function to allocate all qubits.

void deallocate_qubit(unsigned qubit_id)

De-allocate one qubit with a given id.

Parameters

  • qubit_id: ID of the qubit to de-allocate

Exceptions

  • std::runtime_error: if the qubit de-allocation fails either due to the qubit not being allocated or not in a classical state.

void H(unsigned qubit_id)

Apply a Hadamard gate.

Parameters

  • qubit_id: ID of a qubit

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

void S(unsigned qubit_id)

Apply an S gate.

Parameters

  • qubit_id: ID of a qubit

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

void X(unsigned qubit_id)

Apply a X (or NOT) gate.

Parameters

  • qubit_id: ID of a qubit

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

void CNOT(unsigned control_qubit_id, unsigned target_qubit_id)

Apply a controlled-NOT gate.

Parameters

  • control_qubit_id: ID of the control qubit

  • target_qubit_id: ID of the target qubit

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

std::vector<bool> measure_qubits_return(std::vector<unsigned> const &qubit_ids)

Apply measurement gates to a set of qubits.

Return

Array of the measured values

Parameters

  • qubit_ids: Array of qubit IDs

Exceptions

  • std::runtime_error: if any of the qubit IDs are invalid

bool measure(unsigned qubit_id)

Apply a measurement gate to a single qubit.

Return

Measured value

Parameters

  • qubit_id: ID of a qubit

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

bool get_classical_value(unsigned qubit_id, calc_type tol = 1.e-12)

Get the classical value of a qubit.

Return

Classical value of the qubit

Parameters

  • qubit_id: ID of a qubit

  • tol: Tolerance for floating point comparison

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

bool is_classical(unsigned qubit_id, calc_type tol = 1.e-12)

Test whether a qubit is in a classical state or not.

Return

true/ depending on whether the qubit is in a classical state or not

Parameters

  • qubit_id: ID of a qubit

  • tol: Tolerance for floating point comparison

Exceptions

  • std::runtime_error: if the desired qubit is not already allocated

double get_probability(const std::vector<bool> &bitstring, const std::vector<unsigned> &qubit_ids)

Return the probability of the outcome bit_string when measuring the quantum register qureg.

Return

The required probability

Parameters

  • bitstring: Measurement outcome.

  • qubit_ids: Array of qubit IDs

Exceptions

  • std::runtime_error: if any of the desired qubits are not already allocated

void collapse_wavefunction(const std::vector<unsigned> &qubit_ids, const std::vector<bool> &bitstring)

Collapse a quantum register onto a classical basis state.

Parameters

  • qubit_ids: Array of qubit IDs

  • bitstring: Measurement outcome for each of the qubits

Exceptions

  • std::runtime_error: if any of the desired qubits are not already allocated

void sync()

Flush gate cache.

Implementation details

namespace details

Functions

template<typename func_t, typename array_t>
constexpr void apply_array_func(const array_t &array, typename array_traits<array_t>::type &val)

Apply a function to each element of an array while accumulating the result.

func_t must be a functor class which implements the ()-operator: 

T func_t::operator()( const T& lhs, const T& rhs ) const;

Parameters

  • array: Array of value to apply the function to

  • val: Value used to accumulate the result

Template Parameters

  • func_t: Class implementing a function via the ()-operator

  • array_t: Array class

template<typename func_t, typename array_t>
constexpr void apply_array_func(const array_t &array)

Apply a function to each element of an array while accumulating the result.

func_t must be a functor class which implements the ()-operator: 

T func_t::operator()( const T& lhs, const T& rhs ) const;

Parameters

  • array: Array of value to apply the function to

Template Parameters

  • func_t: Class implementing a function via the ()-operator

  • array_t: Array class

template<typename T>
struct array_traits
#include <helper_functions.hpp>

Trait class to identify array types.

template<typename T, std::size_t N>
struct array_traits<std::array<T, N>>
#include <helper_functions.hpp>

Specialisation to identify std::array.

template<typename T, std::size_t N>
struct array_traits<T[N]>
#include <helper_functions.hpp>

Specialisation to identify C-style arrays.

struct Gates
#include <StabilizerSimulator.hpp>

Gate storage.

Class used to cache gate operations

Public Functions

Gates(unsigned n = 1, unsigned max_d_a = 1)

Constructor.

Parameters

  • n: number of qubits

  • max_d_a: Maximum number of gates to cache

void reset()

Reset the state of the cache.

uint32_t popcnt32(uint32_t a)

Generic implementation of population count for 32-bit unsigned integers.

Only used if if no-intrinsics or compiler builtin can be found

Return

Number of of bit set to 1 in integer

Parameters

  • a: Unsigned integer