Here are links to a videotaped lecture in two parts entitled “why quantum computers cannot work” recorded at the Simons Institute for the Theory of Computing on December 2013 and two additional videos: a short talk on topological quantum computers and a twelve minute overview. Here are the links: Overview, Part I, Part II, Topological QC. (Update, Nov 14: BosonSampling.)
Why Quantum Computers Cannot Work:
Overview and Vision.
Why Quantum Computers Cannot Work I:
From the “Trivial Flow” to Smoothed Lindblad Evolutions
Why Quantum Computers Cannot Work II:
Debate, Reasons to Disbelieve, and Experimentation
Why Topological Quantum Computers Cannot Work
The Geometry of Spacetime is Enabled by the Failure of Quantum Fault-Tolerance
Left: Nick Read; Right The front page of Nick’s 1990 famous paper with Greg Moore on nonabelions, and below his email to me from March 2005 on topological quantum computation. (click for full view.)
Left: the argument regarding topological QC demonstrated via Harris’ famous cartoon. While not strictly needed I expect the argument to extend from qubits to gates as well. Right: a recent discussion with Nick over Shtetl Optimized (click for full view). Update: We are actually not in an agreement as it seems from the above discussion (see the discussion below).
Update (Nov’ 2014): A fifth video, this time in front of a live audience
Complexity and Sensitivity of Noisy BosonSampling
Added later (April 18): Let me quote from what Steve wrote about the videos: The surprising part is the superior production value relative to your typical videotaped lecture (at least for the first overview video). Producing the videos was an interesting and demanding experience and I was certainly happy to read Steve’s description of the production value. (Of course, the main purpose of Steve’s post was to express his disagreement with the content of the videos. See either the post or Co-‘s comment below.)
Also there are two earlier versions of my lecture (in 1-hour format) that were videotaped. The first was taken by Jesus De Loera in Davis. Very interesting shooting-angle and interesting comments by Greg Kuperberg, Bruno Nachtergaele and other participants. The second was taken in Seattle in a UW-PIMS colloquium lecture. Again interesting questions by several participants including James Lee and John Sidles.
(July:) The Simons Institite (almost identical) versions of the movies are now linked from the web-page of my November 15 lecture at SI.
(Added nov 2014): The only difference from the HUJI version is that there are no opening slides and that for the closing slides I used two pictures of my department’s administrative staff.
The administrative crew of the Einstein Institite of Mathematics (click to enlarge)
I thought of it as a nice opportunity to thank our great administrative staff whose part is crucial in the academic endeavor, and this is a good opportunity to thank the staff in my second academic home – Yale University, in the Simons Institute, in many other places.
Alistair Sinclair and the Simons Institure friendly and helpful staff (click for full size)
Following Saharon Shelah: How to watch these videos
(Added Nov 2014)
Saharon Shelah explained in an introduction to one of his books, that instructions on “how to read this book” are actually instruction on “how to not read this book”. If you want to read the book you start on page 1 and read through to the last page. Instructions for “how to read this book” rather tell you how to jump to a place that interests you.
So, in a similar spirit, here are direct links to the different parts of the videos.
Why quantum computers cannot work: Video I:
A brief description of the lecture 0:00-7:50 (Click here to the start)
Part I: Quantum computers 7:50 -12:48 (Click here to start)
Part II Noise, quantum fault tolerance, the quantum fault tolerance barrier, and the “trivial flaw.” Noise, quantum fault tolerance 12:48-16:40; The quantum fault tolerance barrier 16:40; The “trivial flaw” 19:11-27:40.
Part III My conjectures 27:10
(Two qubits behavior; error synchronization; encoded single qubits; Shor/Sure separators and rate.)
Part IV: Smoothed Lindblad evolutions 40:31
(The definition of smoothed Lindblad evolutions, The work with Kuperberg, Response to some concerns, The internal clock of the evolution; physical mechanism)
Ending – Dorit Aharonov’s comment and my response 57:50 .
Why quantum computers cannot work – Video II:
Part V: Conceptual points from the debate 0:00 ;why are classical computers possible? 4:23, locality 7:49, classical simulation of quantum physics 9:19, (typo: “you see it in complexity” should be “you see it in cryptography”) Does no QC means breakdown of QM? 11:41 The story about Kelvin dating the earth 11:53; to which ares of physics impossibility of quantum fault tolerance are relevant 16:38 .
Short Part VI: Quantum computation without quantum fault-tolerance 18:22
Part VII: Reasons to disbelieve, experiments and summary 27:53
Seven reasons for disbelief; Can you hear the shape of a quantum computer?; Can you reverse or permute the arrow of time? noise and symmetry.
Experimentation 34:40: Martinis and other’s attempts at stable qubits based on surface codes, sub-gaussian fluctuations for error-rates in interacting systems.
Pictures from the debate 40:21 (including a few unrelated pictures like a forgotten picture of Avi Wigderson and Oded Goldreich).
Entertaining/educating parts of the debate 49:33 (Including Scott’s famous $100,000 challenge; Aram’s 3-SAT and 2-SAT analogy, a heart breaking eulogy for Conjecture C ; Jesus and the camel, Making formal distinctions, Aram 3-SAT/2-SAT analogy revisited)
Answers to questions 59:51
If it is up to me will I choose QC to exist? Do I build my work on the assumption that QC are impossible? Is the title of the lecture too strong? If there is a physical principle of “no quantum fault tolerance” how come it was not observed before?
Thanks; Ending presentation.
Introduction (0:00) ; The simulation argument (1:34); Other case for which the simulatuin argument applies (4:37); Quantum fault tolerance and geometry (5:52); The vicious circle for quantum computations and new phases of matters (7:20); Directions for further research (11:32) ; philosophical ending (13:17)