Commit c6997a17 authored by Nguyen, Thien Minh's avatar Nguyen, Thien Minh
Browse files

Added an example using bit-flip QEC from std lib 



Signed-off-by: default avatarThien Nguyen <nguyentm@ornl.gov>
parent ddf7d0d9

examples/ftqc_qrt/bit-flip-code.cpp

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#include <qalloc>



// Example demonstrates a simple 3-qubit bit-flip code.

// Compile:

// qcor -qpu aer[noise-model:<noise.json>] -qrt ftqc bit-flip-code.cpp
@@ -93,7 +91,6 @@ __qpu__ void resetAll(qreg q) { 
// Error corrected Bell example:

// Note: the 3-q bit-flip code can only protect against X errors.

__qpu__ void bellQEC(qreg q, int nbRuns) {

  using qcor::xasm;

  int ancQbId = 6;

  for (int i = 0; i < nbRuns; ++i) {

    // Apply H before encoding.

examples/ftqc_qrt/error_correcting_code.cpp

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#include <qcor_qec>



__qpu__ void applyError(qreg q, int qIdx) {

  std::cout << "Apply X error @ q[" << qIdx << "].\n";

  X(q[qIdx]);

}



using namespace ftqc;



int main() {

  auto q = qalloc(4);

  bit_flip_encoder(q, 0, {1, 2});

  std::vector<int> syndromes;

  // If using a perfec simulator, apply a random X error to observe syndrome changes.

  applyError(q, 2);



  // Measure the stabilizer syndromes:

  measure_stabilizer_generators(q, bit_flip_code_stabilizers(), {0, 1, 2}, 3, syndromes);

  assert(syndromes.size() == 2);

  std::cout << "Syndrome: <Z0Z1> = " << syndromes[0] << "; <Z1Z2> = " << syndromes[1] << "\n";

  

  // Recover:

  bit_flip_recover(q, {0, 1, 2}, syndromes);

  // Measure again to check:

  syndromes.clear();

  measure_stabilizer_generators(q, bit_flip_code_stabilizers(), {0, 1, 2}, 3, syndromes);

  std::cout << "AFTER CORRECTION: \nSyndrome: <Z0Z1> = " << syndromes[0] << "; <Z1Z2> = " << syndromes[1] << "\n";

}
 
 No newline at end of file

lib/impl/bit_flip_code.hpp

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#pragma once

#include <qcor_common>



std::vector<std::vector<qcor::PauliOperator>> bit_flip_code_stabilizers() {

  static const std::vector<std::vector<qcor::PauliOperator>> STABILIZERS{

      {qcor::Z(0), qcor::Z(1)}, {qcor::Z(1), qcor::Z(2)}};

  return STABILIZERS;

}



__qpu__ void bit_flip_encoder(qreg q, int dataQubitIdx,

                              std::vector<int> scratchQubitIdx) {

  CX(q[dataQubitIdx], q[scratchQubitIdx[0]]);

  CX(q[dataQubitIdx], q[scratchQubitIdx[1]]);

}



__qpu__ void bit_flip_recover(qreg q, std::vector<int> logicalReg,

                              std::vector<int> syndromes) {

  const bool parity01 = (syndromes[0] == 1);

  const bool parity12 = (syndromes[1] == 1);

  // Correct error based on parity results

  if (parity01 && !parity12) {

    X(q[logicalReg[0]]);

  }



  if (parity01 && parity12) {

    X(q[logicalReg[1]]);

  }



  if (!parity01 && parity12) {

    X(q[logicalReg[2]]);

  }

}



#ifdef _QCOR_FTQC_RUNTIME

namespace ftqc {

__qpu__ void measure_stabilizer_generators(