ch06_02_grover_freq.js

// Programming Quantum Computers
//   by Eric Johnston, Nic Harrigan and Mercedes Gimeno-Segovia
//   O'Reilly Media

// To run this online, go to http://oreilly-qc.github.io?p=6-2
// Note: This sample may vary slightly from the text in the book,
// due to revisions or aesthetic tweaks.

var number_to_flip = 3;
var number_of_iterations = 4;
var num_qubits = 4;
qc.reset(num_qubits);
var reg = qint.new(num_qubits, 'reg')

reg.write(0);
qc.label('prep');
reg.hadamard();
for (var i = 0; i < number_of_iterations; ++i)
{
    qc.label('Amplitude Amplification');

    // Flip the marked value
    reg.not(~number_to_flip);
    reg.cphase(180);
    reg.not(~number_to_flip);
    reg.Grover();

    // Peek at the probability
    var prob = reg.peekProbability(number_to_flip);
    qc.print('Iter '+i+': probability = '+prob+'\n');

    // just space it out visually
    qc.label('');
    qc.nop();
}