Commit dff88b81 authored by Nguyen, Thien Minh's avatar Nguyen, Thien Minh
Browse files

small update to support local single-site exp-val 



Signed-off-by: default avatarThien Nguyen <nguyentm@ornl.gov>
parent 4da104a8

tnqvm/visitors/itensor/mps/ITensorMPSVisitor.cpp

+29 −19
Original line number Diff line number Diff line
@@ -158,6 +158,13 @@ itensor::Index ITensorMPSVisitor::getSiteIndex(size_t site_id) { 


double ITensorMPSVisitor::compute_expectation_z(

    const std::vector<size_t> &in_measureBits) {

  if (in_measureBits.size() == 1) {

    const auto site_idx = in_measureBits[0] + 1;

    auto ket = m_mps(site_idx);

    auto bra = itensor::dag(itensor::prime(ket, "Site"));

    auto Z_op = singleQubitTensor(getSiteIndex(site_idx), Z(in_measureBits[0]));

    return itensor::eltC(bra * Z_op * ket).real();

  } else {

    auto hamOp = xacc::container::contains(in_measureBits, 0)

                     ? singleQubitTensor(getSiteIndex(1), Z(0))

                     : singleQubitTensor(getSiteIndex(1), Identity(0));
@@ -181,6 +188,7 @@ double ITensorMPSVisitor::compute_expectation_z( 
    auto bond_bra = itensor::dag(itensor::prime(bond_ket, "Site"));

    return itensor::eltC(bond_bra * hamOp * bond_ket).real();

  }

}



void ITensorMPSVisitor::finalize() {

  // Assign the exp-val-z (single Composite mode)
@@ -223,6 +231,8 @@ void ITensorMPSVisitor::applyTwoQubitGate(itensor::ITensor &in_gateTensor, 
  // itensor::PrintData(wf);

  auto [U, S, V] = itensor::svd(wf, itensor::inds(m_mps(in_siteId1)),

                                {"Cutoff=", m_svdCutoff, "MaxDim=", m_maxDim});

  // std::cout << "Singular values:\n";

  // itensor::PrintData(S);

  m_mps.set(in_siteId1, U);

  m_mps.set(in_siteId2, S * V);

}