.. title: Quantum Class 14, Thu 2022-10-20
.. slug: class14
.. date: 2022-10-20
.. tags: class
.. category: 
.. link: 
.. description: 
.. type: text
.. has_math: true

.. sectnum::
.. contents:: Table of contents
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Followup on free-ranging discussion time, 3
=====================================================

Accreditation
-------------

Example of students who don't understand accreditation being tricked:

#. In Florida, non-accredited colleges say that their credits "may" transfer to the prestigious state colleges.

#. The credits do not transfer.  There was no quality control or other standards for those credits.   

   
Compiling quantum computer programs
-----------------------------------

#. Executing a Pascal-like program to an actual quantum computer has several steps.

#. The actual quantum computer has physical qbits.

#. Some (but usually not most) pairs of qbits are connected; see the graph description of the quantum computer.

#. A 2-qbit operation like CCNOT can happen only on a connected pair.

#. Not all the quantum operations that we've seen have physical realizations.  Which do depends on the hardware.  IBM is different from IONQ.

#. The user writing the program is properly unaware of any of this.   S/he just uses meaningful variable names and useful ops.

#. Maybe s/he draws a qiskit diagram, which is basically equivalent to the program.

#. The compiler has to:

   a. Translate unrealizable operations into sequences of realizable operations.

   #. Decide how to optimally assign the variables to actual qbits.

   #. Remember that operations can occur only between adjacent qbits, so try to assign qbits to maximize this adjacency.

   #. To operate on other pairs of qbits,  add swap operations to make them adjacent.

   #. These (and all) operations are noisy and take time.

   #. The quantum computer has a limit (the quantum volume) on how much it can do before accumulated noise etc destroys the results.

   #. Look for opportunities to optimize and reduce pairs of consecutive operations.  This happens a lot.

#. Qiskit and its competitors do all this.

#. This is reminiscent of compiling onto a classical machine with limited registers.

#. Optimal solutions are NP, but good enough solutions are possible.

#. Someone is probably using a quantum computer to compile.


Being a grad student here at RPI
--------------------------------

How might we help?

   
Student presentations, round 2
==============================

Pick your date (choices: next Mon or Thurs) and announce your topic here:

   https://doodle.com/meeting/participate/id/dJqLVD2b

When signing up, use enough of your name(s) that I can recognize you, plus your topic.


News
====

#. The Nobel Prize in Physics 2022

   https://www.nobelprize.org/prizes/physics/2022/press-release/

#. New research suggests our brains use quantum computation

   https://phys.org/news/2022-10-brains-quantum.html

#. https://quantumcomputingreport.com/news/

   Note Malta.

#. https://news.mit.edu/topic/quantum-computing

#. https://www.reddit.com/r/QuantumComputing/new/

   can be interesting

#. https://www.reddit.com/r/dwave/new/

   has little traffic

Optimization problems doable with D-wave
========================================

#. Max cut

   https://en.wikipedia.org/wiki/Maximum_cut

#. VLSI Circuit opt
   
   https://www.researchgate.net/publication/262162554_An_Application_of_Combinatorial_Optimization_to_Statistical_Physics_and_Circuit_Layout_Design


#. Spin glass min energy

#. A Quantum Annealing Approach for Fault Detection and Diagnosis of Graph-Based Systems

   https://arxiv.org/abs/1406.7601v2

#. https://docs.dwavesys.com/docs/latest/handbook_problems.html#cb-probs-scheduling


D-Wave
======

We'll go thru

https://docs.dwavesys.com/docs/latest/