Mindscape 153 | John Preskill on Quantum Computers and What They’re Good For

Patreon: / seanmcarroll
Blog post with audio player, show notes, and transcript: www.preposterousuniverse.com/...
Depending on who you listen to, quantum computers are either the biggest technological change coming down the road or just another overhyped bubble. Today we’re talking with a good person to listen to: John Preskill, one of the leaders in modern quantum information science. We talk about what a quantum computer is and promising technologies for actually building them. John emphasizes that quantum computers are tailor-made for simulating the behavior of quantum systems like molecules and materials; whether they will lead to breakthroughs in cryptography or optimization problems is less clear. Then we relate the idea of quantum information back to gravity and the emergence of spacetime. (If you want to build and run your own quantum algorithm, try the IBM Quantum Experience.)
John Preskill received his Ph.D. in physics from Harvard University. He is currently the Richard P. Feynman Professor of Theoretical Physics at Caltech and the Davis Leadership Chair at the Institute for Quantum Information and Matter, as well as an Amazon Scholar at Amazon Web Services. Before moving into quantum information, he was a leading researcher in quantum field theory and black holes. He is the winner of multiple bets with Stephen Hawking.
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[@yrebrac]

Sean Carroll has a discussion with yet another person I would love to hear Sean Carroll to have a discussion with.

[@crbradbury8282]

Its polite and even more jamm packed with info in this form. Hear ya' though!

[@ErnestGWilsonII]

Q. What happens when you call for tech support on your quantum computer? A. Your quantum computer remains both broken and fixed, we won't know the outcome until the technician collapses.

[@ddavidjeremy]

I love that joke!

[@tjthreadgood818]

Hehe … larious

[@trucid2]

My computer already does this. It works but only when the tech person is looking.

[@bambulablackbass760]

😂😂😂😂

[@Vatsek]

You are not sure if the computer even existed.

[@RonVolkovinsky]

Ha, I bet Sean was beaming 20 minutes in when Dr. Preskill described himself as an Everettian!

[@SolSystemDiplomat]

Looking forward to the listen. Thank you.

[@jessetrott2549]

BADASS MAN - THIS HAS TO BE ONE OF THE BEST AND COULD USE 4 HRS

[@szclimber]

amazing guest and conversation

[@David-tp7sr]

Thank you so much for all your podcasts Mr. Sean Carroll. You do service to humanity.

[@Saptarshi.Sarkar]

Exactly what I was looking for!

[@desgreene2243]

Great podcast - keeping expectations of Quantum Computing grounded but tacitly revealing incredible potential.

[@JimGobetz]

That was interesting. Thanks as always Sean

[@martinds4895]

Great episode !! Thanks Sean 😀

[@sidg11]

I'm calling it, this will be one of your most popular podcasts

[@dajandroid]

Wonderful guest! timely for me.

[@rsmith16384]

Professor Carroll, great episode! Please revisit this topic. Would really like to hear from someone working on post quantum cryptography standards now being developed.

[@mokopa]

I find that playing soft classical or jazz music in ambience enhances the experience and aids with contemplation

[@korbindallas8224]

You're so refined

[@StayPrimal]

I'm so happy that you keep posting, even ''post'' covid.

[@fyohox742]

Thank you

[@ddavidjeremy]

Really enjoyed this podcast. I am still absolutely clueless how a quantum computer works. I will keep trying till the light bulb turns on though.

[@tjthreadgood818]

It IS a bit like “spooky action” … close at hand.

[@sokasbogo6912]

Can u seperate string theory into two after giving a single parametr and bring out our universe.

[@UtraVioletDreams]

Yes, As a developer I've been experimenting with IBM Q.

[@ALINAXANGELINA]

So interesting!

[@BikermanCoUk]

I just lost my quantum computer! I checked to see if it was on, and now I don't know where it is...

[@bhatmuzamil6221]

great sir

[@bennguyen1313]

Regarding the 42m mark on how the scaling a quantum system will lead to interactions with the environment, thus will lead to decoherence.. it reminds me of how Ramachandran says that science, especially biology, can provide answers to very detailed, precise questions, but cannot answer the most basic of questions at the organism level. James Altucher shares a similar idea (#730 1h42m). Finally, I highly recommend Sabine Hossenfelder's "Quantum Computing: Top Players 2021" for a short masterclass on quantum computers!

[@BikermanCoUk]

quantum computers are a pain. Every time you look at the monitor you have to save your changes....

[@rey82rey82]

The set of all possible traveling salesmen problems

[@DontKnowHowToSayNo]

Listen to 1:20:15 to 1:20:45

[@bigradio9396]

Random question: if a pair of entangled particles pop into existence near the event horizon of a black hole a la Hawking radiation mechanism and one escapes and the other doesn’t and the trapped entangled particle meets another particle that affects its spin let’s say, the entangled particle outside the event horizon would also then have its spin affected. Doesn’t that mean that Information escaped rhe black hole?

[@mangoatree]

How would you find out if the spin was changed? There is no way for you to know what the state was initially so there is no information in measuring the spin of the particle which survived outside of the black hole. To you the outcome will still look random. Does that make sense?

[@bigradio9396]

@@mangoatree Thanks, Mangoatree. I hear that, however the problem still nags at me. A black hole has mass (probably not a controversial statement) so it's reasonable to expect our entangled trapped particle to come into contact / interact with another particle / force inside the event horizon. While we're not looking, the fact remains that any interaction inside the black hole will affect the entangled particle outside of it, somehow breaking the fundamental statement that nothing can escape a black hole. The escaped particle can also be expected to react with something, therefore information would be preserved (as the spin of the escaped particle was set by the interaction by the trapped particle). While consciousness is not at play, the effect is information.

[@disconat]

You will never be able to convince me that Sean wasn't talking to Jeff Bridges. Preskill sounds JUST Like him

[@nowhereman8374]

If decoherence of the qubits are such a problem, why not try and isolate the bits in outer space and use the vacuum for 'coherent isolation'?

[@primus4cameron]

What vacuum. You mean the one containing (a low density of) hydrogen and helium, not to mention electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays?

[@nowhereman8374]

@@primus4cameron Yup, solar wind would be a problem (neutrinos no, lol), but in general many magnitudes lower density would improve coherence times. With magnetic confinement, it should able to keep the qubits(for example, ions) isolated. How much you want to bet there is a Darpa project out there somewhere?

[@AbhishekKumar-eh7zx]

That would defeat the entire purpose of having a quantum computer. Imagine doing this for hundreds/thousands of qubit while doing computations on them

[@nowhereman8374]

Don't be so sure there isn't a DARPA out there

[@zip8444]

If it would take all the classical computers in the world 10^100 years to get the right answer, how would you know the quantum computer's answer -- calculated in a few seconds or hours -- would be the correct answer? Just asking!

[@bitdribble]

Just multiply the factors discovered by the quantum factorization Algo, and check it's the original number

[@crustacea3967]

try to factorize 2491. It would take you a while. But if I say you that the answer is 47 and 53, you could promptly calculate 47*53 = 2491 in seconds

[@viralsheddingzombie5324]

A processor or hardware platform is only half of a system. An operating system is necessary to make it workable. So, is it even possible to design software to retain the alleged advantages of a quantum processor?

[@AbhishekKumar-eh7zx]

Right, so the research community is not only working on hardware part but other aspects too. For example one research group ( I can't recollect the name right now), is working on developing the quantum internet protocol stack for quantum communication. Similarly we are also investigating aspects like quantum ML, crypto etc. We can also simulate such algos on IBM Q. The thing is that software part is somewhat easy to achieve, it's the actual realization of the hardware for Quantum computing that's very tricky and technology and cost intensive.

[@DKamps]

What is a quantum computer?

[@lukewormholes5388]

good to listen to a science podcast where no one talks about aliens

[@chrisofnottingham]

Many people still think that a quantum computer is essentially a laptop with better transistors.

[@ChristopherDeanHoward]

I know this is about Quantum Computing, but I still just can't get over the fact that Sean believes time is an actual real thing, as opposed to what it clearly actually is: an entirely human conception.

[@johnimusic12]

Time is just a word we assign to the evolution of causality.

[@uninspired3583]

@@johnimusic12 thats what words are though, arbitrary assignments to describe ideas. The point here is that perceptions themselves are arbitrary representations, and not at all like reality. We perceive a color, but light is electromagnetic radiation. Our concept of time could be like this, where our perception is very different from what it is outside our minds

[@crustacea3967]

@@uninspired3583 yeah, but color is real (a projection of the light spectrum into the visible spectrum) and time too (a dimension in general relativity). "real" is what is useful to make prediction. It's hard to evolve into a species that feels only random things, although with goddy and religious things we have tried really hard to become one

[@uninspired3583]

@@crustacea3967 we're using the word real differently. The way it's often used in philosophy is to mean things that exist outside of minds. In that respect, color isn't real, its imagination that corresponds with electromagnetic wavelength. The fact that it is imaginatory doesn't mean its completely random, it's internally consistent. We don't know that we have the same perceptions, it's possible that if you were to have access to my perception, the pallet could be entirely different. We both agree on what a certain wavelength is called so in that respect there is consistency, but our internal perception could be entirely arbitrary.

[@HakWilliams]

So, quantum computing will never really work because we don't live in anti-de Sitter space?

[@justinbaker2883]

I feel like this wont get off the ground until AI can enter and give us solutions we couldn't envision. But wonder if we cant have AI until we figure out QC. Could be the chicken and egg that holds us back.

[@Sunil.physics]

please post video as well .

[@_ARCATEC_]

💓 We are in a Blackhole.

[@sgtshatta01]

He said lasers have frequencies? I think he meant to say wavelengths!

[@realcygnus]

They have both since the two quantifiable properties are interchangeable via c.

[@element4element4]

Frequency and wavelength of a wave are related through the velocity of the wave. Since light always moves with the same velocity, speed of light, then you can equally well use wavelength or frequency to talk about monochromatic light or lasers.

[@crustacea3967]

frequecy*wavelength = speed of the wave

[@lucamatteobarbieri2493]

Ai can benefit from quantum computers

[@viralsheddingzombie5324]

quantum computing sounds like trickery. I just don't buy the concept of superposition. What seems to underlie the claimed advantage of quantum hardware is the use of unique materials that allow faster processing in parallel. So the performance advantage is really in the materials rather than the mysterious concept of superposition. Superposition implies, in a binary system, that there is a third quantum state that could represent 1 or 0 at the same time. But in reality, at some point the decision to select 1 or 0 must be made to complete a calculation. I just don't see the increase in efficiency of considering a third state. Superposition is an illusion.