Function main

examples/quantum_computing_ex.cpp:239–335

// ----------------------------------------------------------------------------------------

int main()
{
    // seed the random number generator
    rnd.set_seed(cast_to_string(time(0)));

    // Pick out some of the gates we will be using below
    using namespace dlib::quantum_gates;
    const gate<1> h = quantum_gates::hadamard();
    const gate<1> z = quantum_gates::z();
    const gate<1> x = quantum_gates::x();
    const gate<1> i = quantum_gates::noop();

    quantum_register reg;

    // We will be doing the 12 qubit version of Grover's search algorithm.
    const int bits=12;
    reg.set_num_bits(bits);


    // set the quantum register to its initial state
    (i,i, i,i,i,i,i, i,i,i,i,x).apply_gate_to(reg);

    // Print out the starting bits
    cout << "starting bits: ";
    for (int i = reg.num_bits()-1; i >= 0; --i)
        cout << reg.probability_of_bit(i);
    cout << endl;


    // Now apply the Hadamard gate to all the input bits
    (h,h, h,h,h,h,h, h,h,h,h,h).apply_gate_to(reg);

    // Here we do the grover iteration
    for (int j = 0; j < 35; ++j)
    {
        (uf_gate<bits>()).apply_gate_to(reg);
        (w_gate<bits-1>(),i).apply_gate_to(reg);


        cout << j << " probability: bit 1 = " << reg.probability_of_bit(1) << ", bit 9 = " << reg.probability_of_bit(9) << endl;
    }

    cout << endl;

    // Print out the final probability of measuring a 1 for each of the bits
    for (int i = reg.num_bits()-1; i >= 1; --i)
        cout << "probability for bit " << i << " = " << reg.probability_of_bit(i) << endl;
    cout << endl;

    cout << "The value we want grover's search to find is 257 which means we should measure a bit pattern of 00100000001" << endl;
    cout << "Measured bits: ";
    // finally, measure all the bits and print out what they are.
    for (int i = reg.num_bits()-1; i >= 1; --i)
        cout << reg.measure_bit(i,rnd);
    cout << endl;