Leonard Susskind: The Power of Quantum Computers | AI Podcast Clips
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00:00:02.580 | - To my mind, as far as I can tell,
00:00:09.600 | the great power of quantum computers
00:00:11.280 | will actually be to simulate quantum systems.
00:00:14.380 | If you're interested in a certain quantum system
00:00:18.440 | and it's too hard to simulate classically,
00:00:21.560 | you simply build a version of the same system.
00:00:25.520 | You build a version of it, you build a model of it
00:00:27.720 | that's actually functioning as the system,
00:00:30.160 | you run it, and then you do the same thing
00:00:32.600 | you would do to the quantum system,
00:00:34.240 | you make measurements on it, quantum measurements on it.
00:00:37.560 | The advantages, you can run it much slower.
00:00:41.880 | You could say, why bother?
00:00:43.240 | Why not just use the real system?
00:00:45.240 | Why not just do experiments on the real system?
00:00:48.080 | Well, real systems are kind of limited.
00:00:49.620 | You can't change them, you can't manipulate them,
00:00:52.040 | you can't slow them down so that you can poke into them.
00:00:56.120 | You can't modify them in arbitrary kinds of ways
00:00:59.080 | to see what would happen if I change the system a little bit.
00:01:04.080 | So I think that quantum computers
00:01:07.720 | will be extremely valuable in understanding quantum systems.
00:01:14.160 | - At the lowest level, the fundamental laws.
00:01:20.040 | - They're actually satisfying the same laws
00:01:22.240 | as the systems that they're simulating.
00:01:24.840 | - That's right.
00:01:25.680 | - Okay, so on the one hand, you have things like factoring.
00:01:28.760 | Factoring is the great thing of quantum computers,
00:01:33.280 | factoring large numbers.
00:01:35.400 | That doesn't seem that much to do with quantum mechanics.
00:01:38.040 | It seems to be almost a fluke
00:01:39.920 | that a quantum computer can solve
00:01:45.800 | the factoring problem in a short time.
00:01:48.620 | And those problems seem to be extremely special, rare,
00:01:54.200 | and it's not clear to me
00:01:55.980 | that there's gonna be a lot of them.
00:01:58.420 | On the other hand, there are a lot of quantum systems.
00:02:00.880 | Chemistry, there's solid state physics,
00:02:03.600 | there's material science, there's quantum gravity,
00:02:06.700 | there's all kinds of quantum field theory.
00:02:09.340 | And some of these are actually turning out
00:02:12.480 | to be applied sciences
00:02:13.780 | as well as very fundamental sciences.
00:02:15.840 | So we probably will run out of the ability
00:02:20.840 | to solve equations for these things.
00:02:23.520 | You know, solve equations by the standard methods
00:02:25.640 | of pencil and paper,
00:02:27.320 | solve the equations by the method of classical computers.
00:02:31.120 | And so what we'll do is we'll build versions
00:02:34.440 | of these systems, run them,
00:02:37.800 | and run them under controlled circumstances
00:02:39.960 | where we can change them, manipulate them,
00:02:42.520 | make measurements on them,
00:02:43.800 | and find out all the things we wanna know.
00:02:46.240 | - So in finding out the things we wanna know
00:02:49.320 | about very small systems, right?
00:02:52.520 | Is there something we can also find out
00:02:55.960 | about the macro level?
00:02:57.800 | About something about the function,
00:03:00.080 | forgive me, of our brain, biological systems?
00:03:03.800 | The stuff that's about one meter in size
00:03:06.080 | versus much, much smaller.
00:03:08.160 | - Well, all the excitement is about,
00:03:10.920 | among the people that I interact with,
00:03:12.640 | is understanding black holes.
00:03:14.720 | - Black holes.
00:03:15.560 | - Black holes are big things.
00:03:16.760 | They are many, many degrees of freedom.
00:03:20.720 | There is another kind of quantum system that is big.
00:03:24.440 | It's a large quantum computer.
00:03:26.560 | And one of the things we've learned
00:03:28.880 | is that the physics of large quantum computers
00:03:31.440 | is in some ways similar to the physics
00:03:33.320 | of large quantum black holes.
00:03:35.480 | And we're using that relationship.
00:03:37.720 | Now you asked, you didn't ask about quantum computers
00:03:40.480 | or systems, you didn't ask about black holes,
00:03:43.800 | you asked about brains.
00:03:45.680 | - Yeah, about stuff that's in the middle of the two.
00:03:48.040 | - It's different.
00:03:49.800 | - So black holes are, there's something fundamental
00:03:54.320 | about black holes that feels to be very different
00:03:56.960 | than a brain.
00:03:57.920 | - Yes.
00:03:59.000 | And they also function in a very quantum mechanical way.
00:04:01.680 | - Right.
00:04:02.520 | - Okay.
00:04:03.560 | It is, first of all, unclear to me,
00:04:06.360 | but of course it's unclear to me.
00:04:07.840 | I'm not a neuroscientist.
00:04:10.200 | I have, I don't even have very many friends
00:04:13.800 | who are neuroscientists.
00:04:15.920 | I would like to have more friends who are neuroscientists.
00:04:18.320 | I just don't run into them very often.
00:04:20.280 | Among the few neuroscientists I've ever talked about
00:04:24.120 | about this, they are pretty convinced
00:04:28.160 | that the brain functions classically.
00:04:31.440 | That it is not intrinsically a quantum mechanical system
00:04:36.320 | or doesn't make use of the special features,
00:04:39.360 | entanglement, coherent superposition.
00:04:42.160 | Are they right?
00:04:43.120 | I don't know.
00:04:44.680 | I sort of hope they're wrong,
00:04:46.480 | because I like the romantic idea
00:04:48.600 | that the brain is a quantum system.
00:04:50.400 | - Yeah.
00:04:51.240 | - But I think probably not.
00:04:53.520 | The other thing, big systems can be composed
00:04:57.320 | of lots of little systems.
00:04:58.720 | Materials, the materials that we work with and so forth
00:05:03.400 | are, can be large systems, a large piece of material,
00:05:08.400 | but they're big and they're made out of quantum systems.
00:05:10.840 | Now, one of the things that's been happening
00:05:12.880 | over the last good number of years
00:05:16.280 | is we're discovering materials and quantum systems
00:05:20.400 | which function much more quantum mechanically
00:05:23.880 | than we imagined.
00:05:25.320 | Topological insulators, this kind of thing,
00:05:27.720 | that kind of thing.
00:05:29.200 | Those are macroscopic systems,
00:05:30.880 | but they're just superconductors.
00:05:33.560 | Superconductors have a lot of quantum mechanics in them.
00:05:37.580 | You can have a large chunk of superconductor,
00:05:40.720 | so it's a big piece of material.
00:05:42.480 | On the other hand, it's functioning and its properties
00:05:45.320 | depend very, very strongly on quantum mechanics.
00:05:48.520 | And to analyze them,
00:05:49.880 | you need the tools of quantum mechanics.
00:05:52.320 | Bye now.
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