Commit a2140f31 authored by Nguyen, Thien Minh's avatar Nguyen, Thien Minh
Browse files

Fixed quantum arithmetic example: 



- Forgot to modulo the exponential -> overflow (bad)

- Removed zero rotation optimization: this will be performed by optimization passes. Also, the generated circuit will be identical with the Qiskit reference impl.

Signed-off-by: default avatarThien Nguyen <nguyentm@ornl.gov>
parent 1ce4a0cd

examples/qrt/shared/arithmetic.hpp

+39 −24
Original line number Diff line number Diff line
@@ -12,6 +12,18 @@ 
// Classical helper functions: wrapped it in a namespace to bypass XASM.

// These functions are used to construct circuit parameters.

namespace qcor { namespace util {

template <typename T>

T modpow(T base, T exp, T modulus) {

  base %= modulus;

  T result = 1;

  while (exp > 0) {

    if (exp & 1) result = (result * base) % modulus;

    base = (base * base) % modulus;

    exp >>= 1;

  }

  return result;

}



// Generates a list of angles to perform addition by a in the Fourier space.

void genAngles(std::vector<double>& io_angles, int a, int nbQubits) {

  // Makes sure the vector appropriately sized
@@ -80,9 +92,9 @@ inline void calcNumBits(int& result, int N) { 
  result = count;

}



// Compute a^(2^i)

inline void calcExpExp(int& result, int a, int i) {

  result = std::pow(a, std::pow(2, i));

// Compute a^(2^i) mod N

inline void calcExpExp(int& result, int a, int i, int N) {

  result = modpow(a, 1 << i, N);

}

}}
@@ -98,16 +110,10 @@ __qpu__ void phiAdd(qreg q, int a, int startBitIdx, int nbQubits, int inverse) { 
  qcor::util::genAngles(angles, a, nbQubits);   

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

    double theta = (inverse == 0) ? angles[i] : -angles[i];

    // If theta is zero, just ignored.

    double eps = 1e-12;

    // FIXME: XASM handles if conditional

    int opCount = (abs(theta) < eps) ? 0 : 1;

    for (int ii = 0; ii < opCount; ++ii) {

    int idx = startBitIdx + i;

    U1(q[idx], theta);

  }

}

}



// Controlled add in Fourier Space

__qpu__ void cPhiAdd(qreg q, int ctrlBit, int a, int startBitIdx, int nbQubits, int inverse) {
@@ -116,11 +122,6 @@ __qpu__ void cPhiAdd(qreg q, int ctrlBit, int a, int startBitIdx, int nbQubits, 
  

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

    double theta = (inverse == 0) ? angles[i] : -angles[i] ;

    // If theta is zero, just ignored.

    double eps = 1e-12;

    // FIXME: XASM handles if conditional

    int opCount = (abs(theta) < eps) ? 0 : 1;

    for (int ii = 0; ii < opCount; ++ii) {

    int idx = startBitIdx + i;

    // Note: ctrlBit must be different from idx,

    // i.e. ctrlBit must not be in the bitIdx vector
@@ -128,11 +129,25 @@ __qpu__ void cPhiAdd(qreg q, int ctrlBit, int a, int startBitIdx, int nbQubits, 
    CPhase(q[ctrlBit], q[idx], theta);

  }

}



__qpu__ void ccPhase(qreg q, int ctl1, int ctl2, int tgt, double angle) {

  CPhase(q[ctl1], q[tgt], angle/2);

  CX(q[ctl2], q[ctl1]);

  CPhase(q[ctl1], q[tgt], -angle/2);

  CX(q[ctl2], q[ctl1]);

  CPhase(q[ctl2], q[tgt], angle/2);

}



// Doubly-controlled Add operation in Fourier space

__qpu__ void ccPhiAdd(qreg q, int ctrlBit1, int ctrlBit2, int a, int startBitIdx, int nbQubits, int inverse) {

  qcor::Controlled::Apply(ctrlBit2, cPhiAdd, q, ctrlBit1, a, startBitIdx, nbQubits, inverse);

  std::vector<double> angles;

  qcor::util::genAngles(angles, a, nbQubits);  

  

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

    double theta = (inverse == 0) ? angles[i] : -angles[i] ;

    int idx = startBitIdx + i;

    ccPhase(q, ctrlBit1, ctrlBit2, idx, theta);

  }

}



// Doubly-controlled *modular* addition by
@@ -271,7 +286,7 @@ __qpu__ void periodFinding(qreg q, int a, int N) { 
  // Apply the multiplication gates

  for (int i = 0; i < 2*n; ++i) {

    int aTo2Toi = 0;

    qcor::util::calcExpExp(aTo2Toi, a, i);

    qcor::util::calcExpExp(aTo2Toi, a, i, N);

    // Control bit is the upper register

    int ctrlIdx = upStart + i;

    cMultModN(q, ctrlIdx, aTo2Toi, N, downStart, downSize, auxStart, auxSize);

examples/qrt/simple/period_finding.cpp

+4 −4
Original line number Diff line number Diff line
@@ -2,10 +2,10 @@ 


// Compile:

int main(int argc, char **argv) {

  // Allocate 18 qubits required for a 4-bit number (4n*2)

  auto q = qalloc(18);

  int a = 4;

  int N = 15;

  // Allocate 22 qubits required for a 5-bit number (4n*2)

  auto q = qalloc(22);

  int a = 11;

  int N = 21;

  // Call entry-point kernel

  periodFinding(q, a, N);