I just came back from Rio from a great congress. Many great talks and many exciting meetings with old and new friends. I had planned to live-blog on the last four days of the congress but on Monday evening I realized that this was an unrealistic task and decided instead to blog only on a single day – Monday. A little later I realized this was also unrealistic and decided to limit my blogging to a single great lecture by Peter Kronheimer and Tomasz Mrowka on Knots, three-manifolds and instantons. But in the end I did not live-blog at all. Let me mention that in the talk by Kronheimer and Mrowka (as in others) a two-speaker talk worked beautifully. It could be a good similar idea to even share a single Fields medal between two (or more) coauthors.

## My lecture

Here are the slides for my lecture Noise Stability, Noise Sensitivity and the Quantum Computer Puzzle.

## Plans for a **Combinatorial Reception** at Saint Petersburg ICM 2022.

There were many national receptions at the ICM (I missed a few but made it to the Abel reception and Japan’s reception). This led to the idea of having a reception by a mathematical discipline. We are thinking of a combinatorial event in ICM2022 as follows:

**Time:** Tuesday evening – the second week of ICM 2022

**Location:** A park in Saint Petersburg (TBA)

**Activity** (tentative): Light food and drinks will be available (to buy). **Music with a DJ and dancing.**

**Invitees** (tentative): The event will be open for all interested ICM2022 participants.

**T-shirts** (very tentative, other suggestions welcome)

background colors: red, blue, white and rainbow

## Combinatorics at ICM 2018

ICM 2018 could be considered as an excellent conference in combinatorics on its own. There were eleven top-of-the-line speakers (one joint with probability) in wide areas of combinatorics who gave very good talks; a separate session of much combinatorial content on theoretical computer science; many lectures in other sessions (alas, a few conflicting) with interest to combinatorialists; and, in addition, many of the plenary talks had a strong combinatorial content or connections. Like for ICM2010 (Post 1 Post 2) I do plan to write more impressions from ICM2018 at a later time. Meanwhile, a few pictures (more, later).

## A Few Pictures from ICM-2018 lectures

All of this obsession over “quantum” is just a scam, like the National Quantum Initiative. Apparently, a couple of dumb Republicans want to waste taxpayer money. I remembered a time when Republicans were actually conservative.

http://scipol.duke.edu/content/first-look-national-quantum-initiative-act-s-3143-hr-6227-115th-congress

I agree with Nobel Laureate Robert Laughlin that quantum computers are the perpetual motion machines of the 21st century. Essentially, researchers are rediscovering the limits of analog computing. Strictly speaking, quantum mechanics only gives the expectations of observables and Turing complexity arguments can’t simply be run backwards. The Born rule is metaphysical fluff, while amplitudes can be positive, negative, spinor, vector or complex. Amplitudes interfere and not probabilities. Probability is only an interpretation and the uncertainty principle does not imply computational speedups. Probability is used in quantum mechanics for the same reason it’s used in classical physics, namely to account for variations in experimental outcomes. Unlike Gil Kalai and Bill Unruh, I think quantum computers aren’t going to work from an epistemic account of quantum mechanics. Also, like Paul Davies, I think their exponentially large states are unphysical. They grow absurdly large by the time you reach 400 qubits. Quantum security is also a scam that does not provide provable real-world security and routing, while quantum-proof classical algorithms already exist alongside perfectly-working key exchange (not even strictly needed for XOR encryption with a one-time trusted physical exchange). It’s a waste of money and STRICTLY goes beyond the predictions of quantum mechanics. That is a FACT.

Mathew, thanks for your comment. The quantum computer endeavor is certainly a high risk huge gain proposal. There are many researchers who do not share (some even dismiss) the view that they are infeasible. In view of this fact, and the fact that investment in science and technology of QC may lead to other fruits I find the current few billions dollars a year world wide investment reasonable. In particular, I like the fact that many huge companies like IBM, Microsoft Google Alibaba and Intel invest in these efforts, and this also serves as strong signal for their strength and long term ambitions.

My own analysis of NISQ-quantum devices gives a good argument that it will not be possible to use them for demonstrating quantum supremacy or used them to build good quantum error correcting codes. If I am correct the efforts to control 70 qubits systems of to build distance 5 surface codes will flatly fail. I expect that even for 20 qubits systems (and realizations of distance 3 surface codes) will fail to well approximate the desired pure states. Certainly I will not support raising the spending on QC to the level of hundreds of Billions of dollars before a good demonstration of 20 qubits systems will be achieved :).

Actually some months ago our PM Netanyahu announced that Israel will spend many hundreds of millions of dollars per year on quantum computers related efforts. Some people asked me about it and I said, that beside the point of view which is clearly expressed in my papers, and the fact that other researchers disagree with me (or even dont give much weight to my analysis) I dont have more to add on this proposed spending.