int main() {
// inverse temperature
double beta = 1 / T;
// random number generator
boost::mt19937 eng(SEED);
boost::variate_generator<boost::mt19937&, boost::uniform_real<> >
random_01(eng, boost::uniform_real<>());
// spin configuration
std::vector<int> spins(L);
for (int s = 0; s < L; ++s) spins[s] = (random_01() < 0.5 ? 1 : -1);
// measurement
double ene = 0;
double mag = 0;
double mag2 = 0;
double mag4 = 0;
// timer
boost::timer tm;
for (int mcs = 0; mcs < MCSTEP + MCTHRM; ++mcs) {
for (int s = 0; s < L; ++s) {
double diff = 2 * spins[s] * (spins[left(s)] + spins[right(s)]);
if (random_01() < 0.5 * (1 + std::tanh(-0.5 * beta * diff))) spins[s] = -spins[s];
}
if (mcs >= MCTHRM) {
double m = 0;
double g = 0;
for (int s = 0; s < L; ++s) {
g -= spins[s] * spins[right(s)];
m += spins[s];
}
g /= L;
m /= L;
ene += g;
mag += m;
mag2 += m * m;
mag4 += std::pow(m, 4);
}
}
// output results
std::cout << "Energy = " << ene / MCSTEP << std::endl;
std::cout << "Magnetization = " << mag / MCSTEP << std::endl;
std::cout << "Magnetization^2 = " << mag2 / MCSTEP << std::endl;
std::cout << "Magnetization^4 = " << mag4 / MCSTEP << std::endl;
std::cout << "Binder Ratio of Magnetization = " << mag2 * mag2 / mag4 / MCSTEP << std::endl;
std::cerr << "Elapsed time = " << tm.elapsed() << " sec\n";
return 0;
}
void prepare_data(string filename)
{/*{{{*/
// create defect center
double x = 0.0, y = 0.0, z = 0.89175;
vec coord; coord << x << y << z;
NVCenter nv(NVCenter::N14, coord);
double magBx = 0.0, magBy = 0.0, magBz = 1e-5;
nv.set_magB(magBx, magBy, magBz);
nv.make_espin_hamiltonian();
cout << nv.get_eigen_state(0) << endl;
cout << nv.get_eigen_state(1) << endl;
cSPIN espin=nv.get_espin();
PureState st0(nv.get_eigen_state(0));
PureState st1(nv.get_eigen_state(1));
espin.set_coordinate(coord);
cout << "espin coordinate = " << espin.get_coordinate() << endl;
// create bath spins
cSpinSourceFromFile spin_file(filename);
cSpinCollection spins(&spin_file);
spins.make();
vector<cSPIN> sl = spins.getSpinList();
cout << sl[0].get_coordinate() << sl[0].get_gamma() << endl;
cout << sl[1].get_coordinate() << sl[1].get_gamma() << endl;
vec magB; magB << magBx << magBy << magBz;
SpinZeemanInteraction zee(sl, magB);
SpinDipolarInteraction dip(sl);
DipolarField hf_field0(sl, espin, st0);
DipolarField hf_field1(sl, espin, st1);
Hamiltonian hami0(sl);
hami0.addInteraction(zee);
hami0.addInteraction(dip);
hami0.addInteraction(hf_field0);
hami0.make();
Hamiltonian hami1(sl);
hami1.addInteraction(zee);
hami1.addInteraction(dip);
hami1.addInteraction(hf_field1);
hami1.make();
cout << hami0.getMatrix() << endl;
cout << hami1.getMatrix() << endl;
Liouvillian lv0(hami0, SHARP);
Liouvillian lv1(hami1, FLAT);
Liouvillian lvH = lv0 - lv1;
double rate = 2.0*datum::pi*1e4;
vec axis; axis << 1.0 << 1.0 << 1.0;
SpinDephasing dephasing(sl, rate, normalise(axis));
LiouvilleSpaceOperator dephaseOperator(sl);
dephaseOperator.addInteraction(dephasing);
dephaseOperator.make();
QuantumOperator lv = lvH + dephaseOperator;
lv.saveMatrix("lv");
vec _bath_polarization = zeros<vec>(3);
SpinPolarization p(sl, _bath_polarization);
DensityOperator ds(sl);
ds.addStateComponent(p);
ds.make();
ds.makeVector();
cout << ds.getVector() << endl;
cout << ds.getMatrix() << endl;
}/*}}}*/