What You Shouldn't Know About Quantum Computers

&gt; Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060.<p>I am skeptical. 36 years is a long time, but in the past 10 years there hasn&#x27;t been much progress:<p><pre><code> year 2001: factorization of 15 (IBM) year 2012: factorization of 21 (University of Bristol) year 2019: factorization of 35 attempt, failed (IBM) </code></pre> <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Shor%27s_algorithm#Physical_implementation" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Shor%27s_algorithm#Physical_im...</a>

At first I thought that the introduction was hyperbole, but the write-up does actually more or less deliver on it. Written in plain English that anyone can grok, it&#x27;s a good summary of what quantum is, what it isn&#x27;t, and why you should care. Definitely recommend reading if, like me, you&#x27;re not too familiar with the field.

&gt; For example, would quantum computers work by trying all possible answers in parallel? Sorry, no, that&#x27;s too good to be true: Quantum computers work by choreographing a pattern of interference, where the contributions to the amplitude of each wrong answer cancel each other out, while the contributions to the right answer&#x27;s amplitude reinforce each other. Only for special problems, as it turns out, do we know how to choreograph such an interference pattern to deliver a huge speedup over the best known classical algorithms. This, in turn, is why we don&#x27;t expect quantum computers ever to replace classical computers, but “merely” to complement them, accelerating specific tasks like quantum simulation and codebreaking.<p>I&#x27;m not sure about the field of physics but in deep learning there are hundreds of papers published every day while no more than a percent of them tries to make the paper less mythical and instead they keep inventing buzzwords and claiming positive results to make them even more mythical

The article suffers from skipping between layers of abstraction in an attempt to make a point, and in the end in doing so fails to make the initial point.<p>In the first &quot;Myth&quot; section, that &quot;nobody understands this quantum stuff&quot;, the example is used of the transistor. It&#x27;s true that we have no way of making a classical model of a transistor, and our understanding of how transistors work relies on quantum mechanics.<p>But we did not invent transistors from quantum physics -- we created transistors long before we had an explanation of how they worked, and we have continued to improve and iterate by making advances in material sciences and experimentation, not by applying first principles. Things like blue LEDs were invented by tinkering rather than by solving Lagrangians.<p>The final section was of particular interest to me; Gil Kalai&#x27;s work on quantum error correction is very interesting to me and I am in the camp that believes that quantum computing is not possible in any useful sense; in particular a quantum computer will not be capable of being significantly more powerful than a classical computer, in the quantum supremacy sense.<p>Here the author reverts to a simplistic argument that &quot;of course&quot; quantum computers are possible, because we can model a quantum computer in a traditional computer. But this sidesteps the main claims, which are whether it is possible to scale error correction to the point where a useful result can be achieved.<p>Even in the domain of NISQ, which is roughly the equivalent of running fluid dynamics simulation in a bathtub, we have yet to produce results showing that we can scale significantly better than a quantum computer.

Chris Ferrie also writes great books about science for babies.<p><a href="https:&#x2F;&#x2F;www.csferrie.com&#x2F;books" rel="nofollow">https:&#x2F;&#x2F;www.csferrie.com&#x2F;books</a><p><a href="https:&#x2F;&#x2F;www.amazon.com&#x2F;Quantum-Computing-Babies-Baby-University&#x2F;dp&#x2F;1492671185" rel="nofollow">https:&#x2F;&#x2F;www.amazon.com&#x2F;Quantum-Computing-Babies-Baby-Univers...</a>

Fwiw, there&#x27;s an event I was just looking at from UCL on the &quot;Future of Quantum Computing&quot; (online webinar), <a href="https:&#x2F;&#x2F;www.eventbrite.co.uk&#x2F;e&#x2F;the-future-of-quantum-computing-tickets-909692955117" rel="nofollow">https:&#x2F;&#x2F;www.eventbrite.co.uk&#x2F;e&#x2F;the-future-of-quantum-computi...</a><p>It&#x27;s a panel headed by Prof Al-Khalili. I suspect it will be a beginner level presentation.<p>&gt;Professor Jim Al-Khalili CBE FRS is a theoretical physicist at the University of Surrey where he holds a Distinguished Chair in physics and leads the Quantum Foundations and Technologies Research Group in the School of Mathematics and Physics. As well as his academic work he is a well-known popular science author and broadcaster on BBC radio and television.<p>No affiliation, just may be of interest.

You have to get to page 25 before it starts being honest about the fact quantum computing is a con.<p>Important Nuance: the research is real, the science is real, but the narrative being sold about the future of quantum computing to ensnare investors is not a reasonable prediction and is a con.

The linked paper touches on quantum error correction but doesn&#x27;t explain what the state of the art is. Has any team successfully demonstrated a single usable logical error-corrected qubit yet? I saw this article two months ago <a href="https:&#x2F;&#x2F;physicsworld.com&#x2F;a&#x2F;why-error-correction-is-quantum-computings-defining-challenge&#x2F;" rel="nofollow">https:&#x2F;&#x2F;physicsworld.com&#x2F;a&#x2F;why-error-correction-is-quantum-c...</a> discussing the topic, but the writing makes it unclear exactly what was achieved by the various groups. Is recovery from a finite number of errors sufficient to make a usable logical cubit, or is more work still left to be done?

It&#x27;s a better use of your time just learning quantum mechanics than reading this book. Even if you give up, you&#x27;ll at least learn some linear algebra along the way.

Thank God someone other than Scott Aaronson is publishing this kind of content. Shetl Optimized is too much of a vanity project to serve as a mainstream resource.

&gt; Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060.<p>Delusional, IMO. Without a proper understanding of how the non-linearity of the macroscopic world arises from the unitarity of QM, any scaling projections are wishful thinking. We just don&#x27;t have a good enough understanding of the measurement problem and decoherence to make such projections.

@dang why was this flagged off the front page? Isn&#x27;t this a blatantly obvious abuse of the flagging system?

Is this really an appropriate use of arxiv? I thought it was for physics preprints. This might be a neat work, but it appears to be a 143 page blog post in a PDF (unless I missed the references section?)

It will never work, the physics is completely wrong.