# Due Wednesday November 25th

For Wed:

• Please know that online FCQs are open.  FCQs are used to evaluate your instructors for promotion and tenure, and to inform the department about their teaching effectiveness.  I, personally, greatly appreciate feedback and work to improve my teaching using your feedback.
• To do:  Try out the Shor’s Algorithm simulation.  More specifically:
• Try to factor 35.  Use 10 qubits in the first register and 6 in the second (this is already set up by default).  Try alpha = 9.  Trace through the outputs and eventually obtain the measurement of the first register at the 5th box.  Make sure you understand what is happening in each step (i.e. use this as an opportunity to review the material from Monday).  Note: The QFT step can be really slow on the online sage server.  (I just timed it at around 15 or 20 seconds.)
• With this measurement, use the 6th box to compute the continued fraction convergents.  Pull out the smallest EVEN denominator and try that as your guess for r in the last box.  Did you succeed in factoring?  If not, try measuring again (no need to re-compute the QFT, just go back one box and measure again), and using the new convergents.  It may take several tries!
• Hand in answers to these questions:
1. If you measure “0”, why is this not helpful?  What other measurements seem to be unhelpful and why?
2. Try alpha = 11 and explain how it fails.  What is wrong with this alpha? (With reference to the proposition that we began Monday’s class with.)
3. Try alpha = 19 and explain how it fails.  What is wrong with this alpha? (Again with reference to the aforementioned proposition.)