Video summary
Leonard Susskind argues that the primary power of quantum computers lies in their ability to simulate complex quantum systems that are too difficult for classical machines to model. Instead of merely solving abstract mathematical problems, these devices function as physical models where users can manipulate variables, slow down processes, and perform measurements on a system that obeys the same fundamental laws as nature itself. This capability is particularly valuable because real-world quantum systems often cannot be easily altered or observed without disrupting them; for instance, one cannot simply pause an experiment to poke into it or change its parameters arbitrarily to test different hypotheses. By building controllable versions of these systems, scientists can explore scenarios that are impossible to investigate through direct experimentation alone. While factoring large numbers is frequently cited as a hallmark application of quantum computing, Susskind suggests this may be a rare exception rather than the rule for future utility. He posits that there will likely not be many other problems with similar special properties available for classical computers to solve efficiently but which only quantum devices can handle quickly. The true promise lies in addressing vast fields such as chemistry, solid-state physics, material science, and even theoretical areas like quantum gravity and field theory. As researchers encounter equations too complex for standard pencil-and-paper methods or classical supercomputers, the solution will be to construct specific models of these systems—such as topological insulators or superconductors—to analyze their properties under controlled conditions. The discussion also touches upon the relationship between large-scale quantum computers and macroscopic phenomena like black holes. Susskind notes a fascinating parallel where the physics governing massive quantum computers mirrors that of large quantum black holes, both possessing many degrees of freedom. This connection allows physicists to use insights from one domain to understand the other, bridging gaps in our understanding of fundamental laws. However, he draws a clear distinction when considering biological systems and the human brain. Unlike black holes or engineered materials like superconductors which exhibit strong quantum mechanical behaviors at macroscopic scales, there is currently no consensus that brains function as intrinsically quantum systems utilizing entanglement or coherent superposition. Despite his personal hope for the romantic idea of a quantum brain, Susskind acknowledges that most neuroscientists he has consulted believe the brain operates classically rather than relying on special quantum features. He admits this view is not entirely settled but leans toward agreement with them while noting that macroscopic materials are indeed composed of microscopic quantum systems. The discovery of new materials like topological insulators demonstrates how large chunks of matter can function in ways heavily dependent on quantum mechanics, requiring advanced analytical tools to understand. Ultimately, the field stands at a crossroads where we must determine whether nature's most complex structures, from black holes to biological entities, utilize unique quantum advantages or if their behavior is adequately described by classical physics emerging from underlying quantum components.
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my mind as far as I can tell the great
power of quantum computers will actually
be to simulate quantum systems if you're
interested in a certain quantum system
and it's too hard to simulate
classically you simply build a version
of the same system you build a version
of it you build a model of it that's
actually functioning as the system you
run it and then you do the same thing
you would do the quantum system you make
measurements on it quantum measurements
on it the advantages you can run it much
slower you could say why bother why not
just use the real system why not just do
experiments on the real system well real
systems are kind of limited you can't
change them you can't manipulate them
you can't slow them down so that you can
poke into them you can't modify them an
arbitrary kinds of ways to see what
would happen if I if I change the system
a little bit so I think that quantum
computers will be extremely valuable in
in understanding quantum systems at the
lowest level the fundamental laws
they're actually satisfying the same
laws as the systems that they're
simulating man okay so in the one hand
you have things like factoring back in
factoring is the great thing of quantum
computers factoring large numbers that
doesn't seem that much to do with
quantum mechanics right it seems to be
almost a fluke that a quantum computer
can solve the factoring problem in a
short time so though and those problems
seem to be extremely special rare and
it's not clear to me that there's gonna
be a lot of them on the other hand there
are a lot of quantum systems chemistry
there's solid-state physics there's
material science there's quantum gravity
there's all kinds of quantum of quantum
field theory and some of these are
actually turning out to be Applied
Sciences as well as very fundamental
Sciences so we probably will run out of
the ability to solve equations for these
things you know solve equations by the
standard methods of pencil and paper
solve the equations by the method of
classical computers and so what we'll do
is we'll build versions of these systems
run them and run them under controlled
circumstances or we can change them
manipulate them make measurements on
them and find out all the things we want
to know
so in finding out the things we want to
know about very small systems right now
the is there something we can also find
out about the macro level about
something about it the function and
forgive me of our brain biological
systems the the stuff that's about 1
meter in size versus much much smaller
well what the only excitement is about
among the people that I interact with is
understanding black holes that falls
black holes are big things there are
many many degrees of freedom there is
another kind of quantum system that is
big it's a large
computer and one of the things we
learned is that the physics of large
quantum computers is in some ways
similar to the physics of large quantum
black holes and we're using that
relationship now you asked you didn't
ask about quantum computers or systems
you didn't ask about the black holes you
asked about brains
yeah but stuff that's in the middle of
the two it's different so but the black
holes are there's something fundamental
about black holes that feels to be very
different than the brain yes and they
also function in a very quantum
mechanical way right okay it is first of
all unclear to me but of course it's
unclear to me I another I'm not a a
neuroscientist I have I don't even have
very many friends who are
neuroscientists I would like to have
more friends who are neuroscientists I
just don't run into them very often
among the few neuroscientists I've ever
talked about about this they are pretty
convinced that the brain functions
classically there is not intrinsically a
quantum mechanical system or doesn't
make use of the of the special features
entanglement coherent superposition are
they right
I don't know I sort of hope that wrong
with just because I like the romantic
idea that the brain is a quantum system
and but I think that but I think it's
probably not
the other thing big systems can be
composed of lots of little systems
materials the materials Arthur that we
work with and so forth are three large
systems and a large piece of material
but they're begging and they're made out
of quantum systems now one of the things
that's been happening over the last a
good number of years is with discovering
materials and quantum systems which
function much more quantum mechanically
then than we imagined topological
insulators this kind of thing that kind
of thing
those are macroscopic systems but they
just superconductors superconductors I
have a lot of quantum mechanics in them
you can have a large chunk of
superconductor so it's a big piece of
material on the other hand it's
functioning and its properties depend
very very strongly on quantum mechanics
and to analyze them you need the tools
of climate annex
you