Performing a Quantum Factorisation

Load circuit.hs an select the Start Simulation option as described above. In the Function field enter the string "qftFactor n", where n is the size of the first register in the circuit. Suggested values for n range between 6 and 14. Select 'input for quantum factorisation'. In the output section select the type of histogram and range the histogram over bits 0 to n-1 (i.e. the first register of the machine). Hit OK to proceed and you will be presented another dialog box requesting the number to factorise, as shown in Figure 36.

The simulation will then start and the results will be output to the main window. Notice that the algorithm has only a 50% chance of succeeding on a given iteration.

The option 'input for quantun factorisation' performs the mapping whereby the initial state of the system is mapped from |a>|0> to |a>|x^a (mod n)>. Ideally the circuit itself would perform this operation. This is left as an exercise for the reader!