Commit 30c01db2 authored by Nguyen, Thien Minh's avatar Nguyen, Thien Minh
Browse files

Heisenberg model factory function to handle generic observable 



Looking for direct Observable params if any, otherwise looking for string key (avg magnetization, staggered magnetization)

Signed-off-by: default avatarThien Nguyen <nguyentm@ornl.gov>
parent bd2c0fe5

lib/qsim/base/qcor_qsim.cpp

+43 −5
Original line number Diff line number Diff line
@@ -50,12 +50,50 @@ ModelBuilder::createModel(ModelType type, const HeterogeneousMap &params) { 
    }



    QuantumSimulationModel model;

    // Observable = average magnetization



    // Handle custom observable:

    qcor::Observable *model_observable = nullptr;

    // Get QCOR Pauli Op first (if any)

    if (params.keyExists<qcor::PauliOperator>("observable")) {

      static auto cached_pauli = params.get<qcor::PauliOperator>("observable");

      model_observable = &cached_pauli;

    }

    // Generic qcor::Observable

    else if (params.pointerLikeExists<qcor::Observable>("observable")) {

      model_observable = params.getPointerLike<qcor::Observable>("observable");

    }

    else {

      const std::vector<std::string> SUPPORTED_OBS{"average_magnetization",

                                                   "staggered_magnetization"};

      std::string observable_type = "average_magnetization";

      if (params.stringExists("observable")) {

        observable_type = params.getString("observable");

      }



      if (!xacc::container::contains(SUPPORTED_OBS, observable_type)) {

        qcor::error("Unknown observable type: " + observable_type);

      }



      auto observable = new qcor::PauliOperator;

      if (observable_type == "average_magnetization") {

        for (int i = 0; i < hs_model->num_spins; ++i) {

          (*observable) += ((1.0 / hs_model->num_spins) * Z(i));

        }

    model.observable = observable;

      }

      else if (observable_type == "staggered_magnetization") {

        double coeff = 1.0;

        for (int i = 0; i < hs_model->num_spins; ++i) {

          (*observable) += ((coeff / hs_model->num_spins) * Z(i));

          // Alternate the sign

          coeff = -coeff;

        }

      }



      model_observable = observable;

    }



    assert(model_observable);

    model.observable = model_observable;

    qsim::TdObservable H = [&](double t) {

      qcor::PauliOperator tdOp;

      for (int i = 0; i < hs_model->num_spins - 1; ++i) {