Quantum Class 5, Mon 20220912
1 Homework 4
You talk next Mon. See here.
2 Quantum computing in the news
(or at least on Slashdot).
3 Abstract computation models ctd
Original motivation was to discover an algorithm for proving (or disproving) theorems.

That can be done in some simple cases, like first order predicate calculus with addition over the integers.
and first order predicate calculus with addition and multiplication over the rationals or reals.

This goal failed because it was proved that it is undecidable in some cases.
like first order predicate calculus with addition and multiplication over the integers.
Some theorems truth or falsity depends on the allowable domain of their variables.
in a deep sense, ints are harder than reals.
Long time ago I wrote a paper on this, in the context of computer graphics. Problems with Raster Graphics Algorithms.
4 Complexity classes
Group problems into broad classes of considerably differing difficulty.
P vs NP.
Steve Cooks's paper first describing this was rejected.
Quantum complexity classes.
5 Hardware implementations
Quantum computation was theoretically started decades before actual quantum computers were designed.
Just like classical computers.
Many competing technologies.
Let the strongest win.
5.1 Superconducting qubits
Dilution fridge: cool by mixing He3 into He4.
Cooper pairs of electrons: pairs of electrons in a metal weakly attract each other. It's a quantum effect.
Josephson Junction.
good ref: A Quantum Engineer's Guide to Superconducting Qubits
5.1.1 Transmon qubit
5.2 Trapped Ion
Proponents say that it's better than transmon qbits.
Trappedion qubit, the maglev train of a quantum computer, 9:34, 20210824.

"To date, we’ve run singlequbit gates on a 79 ion chain, and complex algorithms on chains of up to 11 ions."
5.3 Quantum annealing
This is not comparable to quantum gates and circuits like IBM has.
It minimizes a function by testing many solutions in parallel.
See details in the DWave section.
Qbit count is not comparable to gate models.
They make a different type of quantum computer, called a quantum annealer. They have been in the news lately, e.g.,
https://arstechnica.com/science/2020/09/dwavereleasesitsnextgenerationquantumannealingchip/

Quantum Programming 101: Solving a Problem From End to End  DWave Webinar 54:25.
"Want to learn how to program a quantum computer? In this webinar, we explain how to do so by running through a complete, simple example. We explain how to formulate the problem, how to write it, and how to tune it for best results. "
"This webinar is intended for those with little or no experience programming on a DWave quantum computer. After watching, get free time on Leap, the quantum cloud service at https://cloud.dwavesys.com/leap/signup/ "

Slides from Programming Quantum Computers: A Primer with IBM Q and DWave Exercises by Frank Mueller, Patrick Dreher, Greg Byrd held at PPoPP (Feb 2019) ASPLOS'19 (Apr 2019),
Part 3: DWave  Adiabatic Quantum Programming

DWave factoring tutorial and other demos
including Jupyter notebooks (you have to login for them).
5.4 Photonics
https://venturebeat.com/2020/09/02/xanaduphotonicsquantumcloudplatform/
Uses photonics.
Operates primarily at room temperature.
Up to 24 qbits, gate depth of 12.
Has free SW tools, some of which can compile to other quantum technologies.
Expected good applications: graphs and networks, machine learning, and quantum chemistry.
They expect to scale up better than competing technologies.
Operates at room temperature.