QiskitAerState.h

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#pragma once
 
#ifndef _QISKIT_AER_STATE_H_
#define _QISKIT_AER_STATE_H_
 
#ifndef NO_QISKIT_AER
 
#ifdef INCLUDED_BY_FACTORY
 
#include "controllers/state_controller.hpp"
 
namespace AER {
 
class AerStateFake {
 public:
  virtual ~AerStateFake() = default;
 
  bool initialized_;
  uint_t num_of_qubits_;
  RngEngine rng_;
  int seed_ = std::random_device()();
  std::shared_ptr<QuantumState::Base> state_;
};
 
}  // namespace AER
 
namespace Simulators {
// TODO: Maybe use the pimpl idiom
// https://en.cppreference.com/w/cpp/language/pimpl to hide the implementation
// for good but during development this should be good enough
namespace Private {
 
class QiskitAerState : public AER::AerState {
 public:
  const std::shared_ptr<AER::QuantumState::Base> &get_state() const {
    const AER::AerStateFake *fakeState = (AER::AerStateFake *)(void *)this;
    return fakeState->state_;
  }
 
  double expval_pauli(const reg_t &qubits, const std::string &pauli) {
    if (qubits.empty() || pauli.empty()) return 1.;
 
    const auto &state = get_state();
    if (!state) return 0.;
 
    flush_ops();
 
    return state->expval_pauli(qubits, pauli);
  }
};
 
}  // namespace Private
}  // namespace Simulators
 
#endif
#endif
#endif