Hello, and welcome to the Physics Well Stories
podcast.
I'm Andrew Glester.
It's been a hundred years since Werner Heisenberg,
during a summer retreat on the small island
of Helgoland,
developed the core principles
of quantum mechanics.
His groundbreaking work laid the foundation
for the revolutionary
ideas, which were later expanded upon by Max
Planck, Niels Bohr, and Erwin Schrodinger.
Along with several less noted scientists, of course.
And their work, along with those contemporaries, forever
changed our understanding of the universe.
And as we celebrate this incredible milestone, we'll
also be looking ahead. The Helgoland twenty twenty
five workshop is just around the corner as
part of the International Year of Quantum Science
and Technology.
The workshop is named after the island where
Werner Heisenberg first develops these foundational ideas of
quantum mechanics
and it promises to bring together leading physicists,
some of whom we'll hear from in this
podcast, to explore topics such as quantum computing,
quantum materials, and the philosophical implications
of quantum theory.
It's promising to be a milestone gathering for
shaping the future of quantum research and its
applications
in the twenty first century.
In this episode, I'm delighted to be joined
by 3 brilliant physicists who are helping to
shape that next quantum revolution. We'll hear from
Jack Harris, a physicist from Yale and 1
of the organizers
of the Helgoland twenty twenty five workshop and
Anna Maria Ray,
a professor
in theoretical physics at the University of Colorado
in Boulder
who is, amongst other things, the chair of
the American Physical Society's division in atomic, molecular,
and optical physics. As 2025
is the international year of quantum science and
technology,
Physics World readers can expect even more coverage
of the latest quantum research and how it's
impacting the world on the website and in
the magazine. For now, here's the podcast. And
here's Natalie De Leon.
I am an associate professor of electrical and
computer engineering,
with affiliations in physics and the Princeton Plasma
Physics Laboratory at Princeton University. What does that
mean you do on a sort of day
to day? Oh my gosh.
Well, on a day to day basis, it
really feels like I'm mostly,
you know, putting out fires in my lab
and dealing with my children. But,
but okay. So,
my I guess my lab, broadly speaking, works
on, quantum information science and quantum technologies.
We have sort of a broad scope,
that makes it a little bit hard to
compactly talk about, but,
2 thirds of my lab works on, these
cubits called color centers in diamond. So if
you take a diamond
and you put
flaws in it in very specific ways,
then, you can actually make well behaved qubits
that, that can accomplish really interesting tasks. So
the main thing that we're really focused on
is using a particular flaw called the nitrogen
vacancy center. You punch out 2 carbon atoms,
put in 1 nitrogen, and then there's a
little, there's an empty spot in the lattice
next to it,
and that acts as a good qubit even
at room temperature.
So you have very long spin coherence times
and and ways to manipulate it with lasers,
and we use that for quantum sensing. So
we spend a lot of time,
making NICE NV centers,
figuring out how to integrate them with other
devices, and coming up with new protocols for
how to get new kinds of information,
out of these things. And then
a third of my group works on,
totally different platform,
superconducting
qubits for quantum computing.
So there,
you know, what we do is is build
these,
these little printed circuits,
well, actually, not so little. They're at the
kind of hundred micron scale.
And,
and we send in microwave photons, and we
basically just use those microwaves as, as states
for quantum information processing.
Diamonds,
they're expensive. Right? Yeah. So,
well, expensive,
depends on what your competitive technology is, but
I will also say that the diamonds that
we work with are, primarily
synthetic diamonds.
So,
they're grown by plasma chemical vapor deposition,
and, and we work heavily with, with the
company, Element six, which is based in The
UK,
to try to advance the state of the
art of synthetic diamond.
So I think it's still expensive compared to
silicon,
but it is not nearly as expensive as
you would extrapolate from gemstones if you go
and buy a necklace or something like that,
which is you know, has a completely different
economic scaling.
Is it a very global thinking industry at
the moment? Yeah. Well, I guess the,
maybe the thing that's a little bit confusing
from the outside with quantum technologies is it's
not a single industry per se because there's
really a large number of different kinds of
applications.
So I think quantum computing gets a lot
of attention because you get these very big,
kind of,
landmark results from, large scale processors at Google,
and IBM and and, Continuum and other companies
like that.
But, but there are also a large number
of kind of other players that are trying
to find other applications of quantum technologies like
quantum sensing. And sensing is sort of intrinsically
a very diverse
topic because it doesn't have a single target.
It's not like you're just trying to make
the ultimate sensor for just 1 thing, but
you can find sensors that
are really good in space,
or sensors that actually push the boundaries of,
you know, the most sensitive magnetic field you
can measure,
or sensors that, work a lot better when
they're underwater, you know, or,
or give you a different spatial scale of
resolution than people have been able to achieve
before. So I think there's many different kinds
of applications and,
so that's the good thing. The good thing
is that there's diverse applications and you can
kind of find a niche. The bad thing
is that the only thing that matters at
the end is are you a better sensor.
You know? Nobody cares if You use some
beautiful quantum mechanics to get there.
So there's a lot of very hard nosed
classical engineering
that goes into,
you know, really marching up to the forefront
of what you can do and then kind
of using quantum mechanics to get the last
mile. Are there quantum
research labs in every university? Yeah. Well, I
guess, maybe let me be concrete about what
quantum research means because, on the 1 hand,
of course,
we're celebrating the one hundred years of quantum
mechanics this year, and there are all of
these different activities to do that.
So quantum has been with us for a
long time, and we believe that it is
just the correct description,
of the
world of the physical world around us, and,
and we just use it. Right? And it's
the basis for a very large number of,
you know, the technology that make my laptop
run. For example,
it's, you know, based on our understanding of
materials, which comes from a fundamental
description of matter that comes from quantum mechanics.
So so that's a little bit distinct from,
when I talk about quantum technologies, what I'm
really talking about is sort of this last
twenty or thirty years
of,
scientific and technological development, which is distinct from
the preceding
seventy to eighty years in that instead of
just using quantum mechanics to describe the microscopic,
structure of things and to make predictions.
This really comes from a marriage of,
quantum physics and information science and trying to
think about what the implications are,
on how we do measurement,
what kind of, you know, what the implications
are for, the complexity of computing things,
you know, what it means to send quantum
information over long distances and whether or not
you can gain any functionality
by using kind of the weirdness of quantum
measurement. And I would say that those topics
people really didn't start thinking about until,
the I mean, there were some pioneers before
that that were working on fundamentals,
but, the first concrete proposals for how you
would actually harness quantum mechanics and quantum information
for technologies
were were really thirty, forty years ago.
So if I if I cut the Venn
diagram down to
to the folks that are really working on
quantum information and quantum technologies,
then, yes, I I wouldn't I wouldn't say
definitively that there's, like, 1 in every university,
but I think it it is a pretty
broad group of of people.
And,
and when you look across the landscape, there's
really, you know, quite a few out there,
and it's and it's pretty diverse. You'll find
people in this space across many different departments.
You know, physics, of course, has a
huge, footprint, but there's, I'm sitting in electrical
engineering.
There are computer scientists,
chemists and material scientists. I think there's quite
a few different,
different kinds of people from different trainings and
backgrounds that are looking at these things.
Okay. Is it an exciting thing to work
in?
Yeah. I mean
okay.
I think
I I'm maybe, like, not the best well,
in some ways, I'm the best poster child
for this or I should be a better
poster child because I'm in the chair line
for the division of quantum information. So I
should be like a you know, in the
in the APS. I should be a card
carrying,
rah rah
cheerleader or something.
I but, you know, I've never conceived of
my own research as being
I desperately need to use quantum technologies, and
then that's how we're going to organize things.
I think I tend to think of things
more in terms of, you know,
where are the soft spots
in our knowledge about some topic?
Where is a frontier that would be interesting
to explore?
And, it just so happens that coincident with
whatever stage I am in my career, you
know, the big opportunity space now is applying
these quantum information process these quantum information concepts
and then taking that lens and using it
to think about a large number of topics.
So,
well, let me let me give you a
concrete example. So right now,
we have this big
new effort in the group,
to do,
broadly speaking, condensed matter physics, so to try
to look at some old and open problems
in condensed matter.
And if if the answer was that you
just needed to build a new classical probe,
I would be completely game for that.
But the opportunity that we have figured out
is that, by using these NV centers in
diamond,
you can manipulate them in a particular way
so that you can look for correlations,
between, you know, the measurements that you do
between different NV centers. It's very hard to
imagine how you would do this with something
that didn't look like a qubit.
And when you can measure these correlation functions,
it gives you access to information that you
just can't get otherwise.
So with normal probes, you're always looking at,
you know, I send a beam through it
or something, and then I look at how
the thing scatter,
or I send a current and look at
globally how does the how does the current
change as I change the parameter, and you're
really averaging over all of these correlation functions.
So the ability to go in and really
map the correlations
at these nanometer scale
spatial resolutions and,
you know,
with with relatively high timing resolution is is
sort of a fundamentally new tool that's unlocked
by the fact that we're using these qubits
as sensors.
So now we're just running around and trying
to,
I I love problems with a big graveyard,
so we're so we're looking for graveyard problems,
that have really eluded past tools and, and
applying this
to a a lot of places. And
That's really interesting because it's in the wider
public, quantum is obviously
seen as weird and other and
alternative. In many in many ways, it's used
for pseudoscience and and those sorts of things.
I mean, you're saying you're not a poster
child for it, but, obviously, you are. It
it is the actual
application of it that has interested you in
it, the real world application of it that
has interested you into it rather than just
some sort of fanciful belief that it might
be good. Yeah. I think that is I
had never articulated it this way before, but
I think that's a fair that's a a
fair characterization.
There are a lot of people who get
attracted to the field of quantum mechanics and
quantum information
because of, fundamentals. Right? Like, they like thinking
about the philosophical,
implications
and maybe some of the
metascience that's associated with that.
I've
not ever been that kind of scientist. I'm
I am very much a shut up and
calculate kind of experimentalist.
So,
yeah, I mean, I think for me, it's
more about,
you know, I I I think of the
the fun of physics as partly
running around and getting to take all of
the tools of humanity,
you know, really marching out to the absolute
bleeding edge frontier of all the technology, all
the capabilities that we
have, and then coming up with
a new kind of experiment or a new
way of seeing things
that uses all of that technology.
I mean, okay. This is a maybe a
kind of a trivial example, but
the number of
experiments that we have that are running now
on FPGAs
is immense.
Field programmable gate arrays. So there are these,
you know, specialized chips that you can do
use to do, you know, for example,
fast real time logic.
Nobody invented these things for physics. We don't
care you know, nobody cares about us.
They're they're not trying to invent, you know,
multibillion dollar industries just for, to make physics
happen. But they exist for other purposes.
And then because they exist, that is the,
you know, leading edge of some technological frontier.
And then 1 question is, can we now
use that to enable new experiments?
So, you know, we do stuff like that
all the time,
and quantum information is 1 of those things
that, happens to be very visible.
But I think it would be it would
be less sexy if I ran around talking
about
how our procurement
ability
is, you know, is really important for, experimental
physics. As you say, there were a few
things happening this year.
Helgoland,
excited about that? Yeah. Yeah. It's a it's
a unique
meeting.
It's an entire six days, and,
I am currently in the stage of life
where I am usually not gone from home
for more than two days at a time
because I have 2 small kids.
So I had to commit
to an entire six days in Germany, which
will be, which will be fun. But they
asked very, very far in advance, so that's
why it's possible to do this big,
expansive trip.
Yeah. I mean, I I haven't heard any
more than what was in the informational email
and the poster, and, you know, I read
the,
the article that was at,
Physics World earlier.
So I know kind of the rough scope,
but everybody I I think the the list
of people is really exciting. It is this
set of people that I've mentioned earlier in
the Venn diagram who are really thinking about
quantum information, its applications to technologies and, new
frontiers in science. And then a lot of
the giants in the field who are working
on fundamentals,
you know, in this space over the last
few decades. Are you hoping to make connections
with people for your work, or are you
is it more interest?
What what's your hope for it?
Yeah. I mean, there there are a few
people here that I don't know very well,
but I will say it's a small enough
community that I know most.
I know most of the people on the
list. So in some ways, it feels more
like, when you go to a wedding and
you see all of these cousins that you
haven't seen for a few years.
That sort of dynamic.
Do you think it's important to do these
things,
not sort of in person, but also
in a location that's sort of historically significant?
Yeah. Well, so,
I think it is it will be interesting
to see
how people,
interpret the assignment,
because you sort of have 2 choices. 1
is that you can do a lot of
stuff that's essentially retrospective
and say you know, and trying to fit
things in the context of the last hundred
years,
or you could just talk about
your hottest, you know, results right now. And,
and both things have value,
particularly
at a meeting like this that is, you
know, supposed to be at least a little
bit retrospective. So I'm not sure. I bet
we're going to get a mix.
You know, I I don't feel particularly qualified
to try
to situate my work in a century of
quantum mechanics, so I'm probably just going to
talk about
stuff that's hot off the presses.
But I I can, just eyeballing the list,
I can think of a handful of people
who will probably do a really great job
at, a little bit of the historical context.
Is it somewhere that you would you know,
personally, you would like to go to Helgoland
anyway because of that historical
context? Is it somewhere that, you know, if
you were given some time off, a sabbatical,
maybe you would think, oh, you know, I
I'd like to see the place where this
happened. Yeah. I have to be maximally honest.
I have not spent a lot of time,
thinking about the history of quantum mechanics. I
read Doug Stone's book.
That was pretty much it.
And,
which was really mostly about how Einstein understood
quantum mechanics.
And,
so,
no, this was not on my radar as,
as a destination to go to. My understanding
is that it's not,
it's not the most, like, attractive
vacation destination.
But I I don't know. Maybe I just
said something really impolite about impolite about
Alconite.
But,
no. I mean, I think it will be
a really fun experience
specifically for this conference. You know, the fact
that they're convening,
this kind of particular
cross section of,
of scientists
and,
and then, you know, having them come talk
about a mix of old and new things,
I think, will be really interesting. What are
your hopes for
quantum
physics, quantum mechanics? What what do you think
are the realistic applications that we might have
in the lifetimes of the people listening to
this?
Yeah.
So
okay. In terms of realistic applications,
I think there are clearly a lot of
opportunities
for,
quantum sensors.
You know, if there's
a very high likelihood
that well, okay. We've already seen that
LIGO uses quantum sensing to see something like,
you know, another factor of 8 more of
the universe. There's a very concrete example where
we really where we really want. I wouldn't
be surprised if in our lifetime,
you know, the
redefinition of the second
involved some sort
of quantum metrology
in state of the art clocks.
I,
and I think there will be a large
number of sort of unsung practical applications
like biomedical,
applications of quantum sensors that, you know,
won't get an enormous amount of splashy press,
but where somebody was able to really push
the state of the art by using a
quantum sensor.
On, quantum information processing,
I think it's a really exciting time,
with these large scale quantum processors. And,
the the part that's really
that I always have to remind myself of
is that the kinds of experiments that people
are doing now in both industry and academia,
if you had gone out for jobs
saying that you were going to do that
stuff when I went out for jobs, which
is not that long ago, it was only
eight years ago,
you would have been laughed out of the
room.
You could not have gotten an academic job
less than a decade ago promising to do
the stuff that we're doing now because all
of the experts knew that this was that
it was too hard. It was just too
hard.
So so in some sense, the pace of,
of advance is actually
really amazing and breathtaking,
and it's hard to keep up. You know,
you have to you have to learn completely
new things to be able to understand what's
going on now. And and it's been fun
to sort of, you know, jump on and
run as fast as possible.
But from, I think, the broader public, it
feels like
the pace of advance is very slow
because,
because we don't have
you know, quantum computers are not,
code breaking
and are not, you know, solving the most
important,
kind of chemistry problems for manufacturing
yet. So I think
the big
kind of exciting project for the next
I'm going to be very optimistic and say
decade.
I don't I don't know if I will
regret this, but let's say decade. For the
next decade, we'll be
transitioning
from the quantum processors
just merely doing stuff that is impressive
to actually doing things that are technologically useful
for mankind.
And I think and I think that is
that's kind of clearly the goal.
Nobody has any illusions about that goal. That's,
you know, that's what everybody is is working
towards.
And a big chunk of the project from
here to there
is,
making things like quantum error correction work. You
know, making processors where you can where you
don't have to live with all the errors,
but you actually can correct them in real
time.
And then, in doing so, scale the processors
up to a meaningful size
where you can actually do something useful.
That's not it, Leon. And, if I'm perfectly
honest, the conversation went off on a bit
of a tangent there from this point about
the redefinition of a second, and it made
me think maybe there's a whole podcast in
that later this year. But I wanted to
talk to somebody who was more on the
theoretical side of things. So here's Anna Maria
Ray.
I am a theorist. And I work my
work is on atomic molecular and optical physics.
I work at Gila and NICE.
Gila is a joint institute between
NICE and the University of Colorado at Boulder.
My work,
is trying to understand how we can
harness and understand atom light interactions
and use them to
advance our field,
towards applications such
as precision measurements,
quantum simulation,
and maybe quantum computer in the future. What
I do is that I do theoretical models,
that describe
the interactions
between many atoms,
molecules, or ions,
that are cooled down to vary to to
their ground state close to their ground state,
and we learn how can we use lasers
to manipulate them,
and make them perform
the best they can
towards different tasks. For example, we can use
we want to use atoms to,
be able to record
very
precise
energy spittings between their I mean, atoms have
their energy penties, and we wanted to lock
the laser to this very
to their pristine energy levels.
And we if we measure this energy difference
very precise, we can come up with a
measure of time because their energy and frequency
are related. So this is how we we
use these atolls for atomic clocks that are
in satellites
or,
we want to improve them at the ultimate
level possible.
We also want to use atoms
that we trap with light in what we
call
artificial crystals of light or optical lattice to
emulate the behavior of electrons in solid state
materials,
and because atoms are fully controllable,
more than electrons in this complicated and complex
solid state environment,
We want to use these systems to shed
light on questions
related to the behavior of solid state systems,
such as high temperature superconductivity,
for example,
that, we jet cannot understand.
And when finally we wanted to use the
atoms or ions that we can control with
light,
to engineer, for example, gates and try to
entangle them,
with the goal that maybe in the future,
these systems can be used as,
building blocks for a 1 computer.
You've got stuff that's really, you know, actually
practically happening now with atomic clocks. Mhmm. And
you've got this
hopeful stuff in the future.
How hopeful are you of that future
application?
Well, I think we will need first to
demonstrate,
in my point of view,
applications of entanglement in metrology
in in
and
we have a lot of things to learn
and to control.
So I am more optimistic
that
if we see
that we can use entanglement for improving
clocks or interferometers,
then we will be in a better position
to use them for more complicated
stuff. The problem is that at the moment,
it's not clear what is actually
the best use of a quantum computer. Of
course, there are many proposals and everything sounds
great,
but I think there are a lot of
things that we need to learn. But the
exciting part is that we are,
working on it. There are a lot of
companies that are starting to get interesting
interested in pushing this direction,
and I'm sure that
many, many
top researchers
thinking of how to make something work,
they will make
even if not a quantum computer, but something
very useful,
come up to reality.
To most people, you know, quantum entanglement. Right?
That that's so distant. That's, I mean,
literally at a distance. Right? But it's it's
so far removed from the day to day
of most people's lives.
If you meet somebody who's not, you know,
the host of the Physics World Story podcast
or you meet somebody who's not at a
conference, How do you talk to them about
entanglement? I mean, entanglement is just correlations between
quantum objects
that allow us to actually extract somehow
information of 1 object
from a measurement of the other,
but it's very fragile.
It's subject to quantum rules,
and, therefore, there are a lot of things
that we need to learn
how to
make it work for us.
Yes. Well, I think entanglement
is everywhere.
I mean, an atom the electrons inside an
atom are fully entangled.
I mean, entanglement is part of our day
to day
world.
The problem is that we cannot
harness in the way that is useful.
The problem is that we have our system
and gets entangled with the rest of the
world. And if we want to isolate the
systems and not let us remove the entanglement
with the rest of the world, That's the
hard part. But, if you look at how
atoms are served, they form singlet triplet states.
They're fully entangled,
but they live in this microscopic
object that, we cannot
act I mean,
electrons or
nuclei inside the atoms are really tightly bound,
and therefore,
they can conserve and preserve their entanglement in
a very
good way. The problem, what we are trying
to do is to use objects that are
weakly interacting
and try to make them talk to each
other
only without coupling to the
outward eye or the the environment, the other
the the things that they talk to indirectly,
and that's why it's challenging. So it's not
that the entanglement
is is not the rule in our universe.
Entanglement is there, but we need to learn
how to use it in an appropriate way.
Helga Land. What are you hoping for from
that meeting? It's going to be exciting.
The interesting part
is that, our field
is working in very diverse directions.
And many times when we go to conference,
we only talk to our own group. That
is great,
but many times, the best ideas come
by discussing with other people that are doing
similar but different things. So my hope in
this conference is try to talk to colleagues,
but also learn new things from other people
and try to see if there is some
crosstalk on familiarization
that we can use to make,
each of the different fields grow more thanks
to
information that we get from other disciplines.
Because, I mean, what we have learned during
this hundred years of quantum mechanics has been
amazing,
And
the hope is that in the next hundred
years is going to be
even
better, like, something that we cannot dream of.
I'm not sure if the quantum computer is
going to be what we are going to
be the most proud in hundred years. And
I
hope that in hundred years, if we have
some
way
to use our quantum knowledge
or some
system that can tell us how our universe
work because there are many of the questions
that we
don't know
yet.
And we don't understand,
and maybe we understand them. Then the way
that we
approach
our day to day
technology or the technology that we use every
day is going to radically change.
And do you think it's important to sort
of commemorate these moments in in history, like,
you know, Heisenberg's
discoveries in Helgoland. Do you think it's important
for science to look at the history in
that way? Yes. Because
many times,
history repeats in some way or the other.
And if we are able to understand,
I mean, I think science,
many times
have them
is when something very revolutionary
happens
that, that is when,
we can make a leap. And sometimes revolutionary
thinking
takes
a lot of
effort because we are not necessarily willing to
change the way that we
see signs.
So learning from the past and how this
type
of big leaps
in our understanding happened can tell us a
lot,
for for how to handle them in the
future and ways to try to actually trigger
them because that's what we want. Are you
looking forward to actually going to the island,
though? I know you're looking forward to the
science, but are you looking forward to actually
going to that place? I have not looked
into that in detail. So this is something
that I do only very close to the
conference. So I first look at the science,
and then I look to the actual place.
So, yes, but maybe if I have a
chance, I will I will I will enjoy.
So you when you were growing up, did
you think maybe 1 day I'll be going
to Helgoland to talk about quantum physics with
other people?
No. No. No. No. I mean,
I'm from Colombia.
So, actually,
even when I came to The for me,
even there when I was reading the papers,
the the authors of the papers were like
like gods. I mean, I would I just
I when I came to The US and
had the chance to actually talk in person
with the people who were the authors of
the paper, it was wow.
So, definitely, I never have thought that when
I was. There. They always say don't meet
your heroes. Is there anybody who you've met
and thought, yeah. No. This is someone you
should meet. Anyone you're particularly excited and were
great. 1 person in my career that has
has inspired or what I do because of
his amazing experiments is Junjie, but he's down
in the lab here at JILA. But I
think he's a really remarkable
individual
and a role model
in size for everybody
that can cover many different directions.
So
so but, I mean, I I it's hard
for me to tell
because, I mean, of course, there are
amazing people nowadays that are driving the field
in a way that we can imagine. Even
my students
now,
when I look at them, some of them
are very impressive.
Definitely
much better that what I was or many
of my colleagues at that time. So I
think people are learning and becoming so strong
that, that's what I'm very optimistic that we
will have
a really, really, really impressive,
advances,
as we move forward.
With theorists like Anna Maria Ray and practitioners
like Natalie de Leon
making their way to Helgoland for Helgoland twenty
twenty five later this year. It promises to
be something of a fascinating workshop. And I
wanted to find out more about that, so
I spoke to Jack Harris, one of the
people
involved in organizing it. I'm a professor of
physics at Yale University. Personally,
I,
became a physicist
because of curiosity about quantum mechanics and sort
of what I learned in high school from
semi popular
books,
for general audience. This would be like John
Gribben and Roger Penrose
and,
Paul Davies, folks like that.
So, yeah, I became a physicist because of
curiosity about quantum mechanics and,
maybe the philosophical
side or just the kind of gee whiz
side that it's amazing that the world we
live in seems so familiar is built in
such a peculiar
way. My day to day research is still
partially motivated by that. A chunk of my
research group,
work on experiments that are really motivated by
trying to understand in how big an object
can you see behavior that is quantum mechanical.
Oh,
so how big an object can you see?
Okay. So I have learned that maybe a
helpful 1 helpful way of thinking about this
question
is that it's not like 1 dimensional thing
like. It's not just, oh, well in a
in an atom, oh, but now in a
molecule. There's sort of a couple axes to
think about.
1 is certainly
how big the object is, maybe like in
terms of its mass. That's certainly an important
axis.
Another is maybe how big it is in
space,
which is to say if you've made a
superposition
of an object, the 2 parts of the
superposition separated by 1 nanometer,
1 millimeter, 1 meter. That's an important question.
And then the third question, which is a
little bit more subtle is, okay. You have
a big object. It's spread out over a
lot of distance. But what specifically is the
quantum phenomena
that you are seeing it exhibit?
There's a bit of a hierarchy here.
And 1 way that I like to think
about it is, okay, you do an experiment,
you measure it, the data that you record,
the phenomena that you observe,
what aspects
of quantum
sorry. What aspects of classical intuition
does it require you to abandon?
And some phenomena that are you know, we
think of as distinctly quantum mechanics. Let's say
0 motion.
The idea
that you remove all the energy you can
from an object, and it still got motion.
This certainly comes about from quantum mechanics, but
you get phenomena like that even in classical
mechanics
if you just didn't quite successfully,
cool the object sufficiently. There's, like, a lot
of the quantum fluctuations that you might see
would look just like thermal fluctuations.
And so that's maybe sort of a a
modestly quantum phenomenon.
It's how are you
differentiating between those things? So I gave you
an example of data that you could take,
which would be you know, if you were
very careful, you could say, look, I have
this harmonic oscillator.
I've studied it very carefully. I really carefully
removed all the energy, and it still has
this little bit of motion, which is set
by Planck's constant.
And so you could reasonably claim that you
have seen a quantum mechanical effector.
But a skeptic could say, look,
you know, I don't really believe that quantum
mechanics applies to such big things, and you
just made a mistake, and it's still coupled
to a thermal bath. That's fine.
There are other experiments that you could make,
like, suppose that you, in certain states,
if you measure if you prepare a state
and measure the position and reprepare the state
to measure the position, we all know you
get a certain distribution.
And if you
prepare that state, but sometimes instead of measuring
position, you measure momentum,
You'll also get a distribution.
And quantum mechanics also allows you to prepare
the states and measure some combination of position
and momentum,
some linear combination.
And if you take all of those results,
you know, you'll get distributions for each of
these measurements. None of them are gonna look
particularly exotic. But if you were to say,
what is the underlying distribution,
the simultaneous
distribution of position momentum
that I must have had prior to my
measurements
to give me these outcomes,
you can be,
you will there are,
datasets
where the answer to that question will involve,
like, a negative probability
distribution.
The only way that you could get,
a distribution for momenta that looks like this
and a distribution for positions that look like
this is if the
underlying joint probability
of position and momentum,
involved negative probabilities, which is sort of not
not a real thing. That's not what a
probability is. And so people you could interpret
this as reflecting the fact that it is
not really possible for a system to have
simultaneously,
value of position and momentum.
So that's a sort of, that's data that
you could take, and you would look at
it, and you would say, look. Whether or
not I believe in quantum mechanics, there is
no story
that explains this data
by giving,
the system
actual values of position momentum
independent of my measurements. You say whether or
not I believe in quantum mechanics. I mean,
are there people who don't believe in it?
Not really, but it's still a useful exercise
for a couple reasons.
1 is,
let's say every, I think every most reasonable
people believe that quantum mechanics is an extremely
accurate theory of every system we've applied it
to so far.
But I also think it's safe to say
that, like, we've never had a theory in
all of the history of science that covered
everything. Every theory has had a limited domain
of accuracy.
And so we want to know, like, at
some point, maybe we'll do an experiment that
goes outside the domain of accuracy of quantum
mechanics. And so it's very important to be
able to say,
I saw
phenomenon x. Like, I just my date here's
the data in my lab book that I
saw. Is this or is this not consistent
with quantum mechanics?
And,
so do you we all believe that quantum
mechanics is a pretty good theory, but but
if you believe at some point it's not
going to be accurate, you it's very helpful
to be able to distinguish between what you're
seeing is required by quantum mechanics or contradicts
it.
Another way to answer that question is,
if,
again, like, if you absolutely believe quantum mechanics,
which, you know, I do for all the
all the things that we experiment on,
but
if the apparently weird data that you take
does have, in principle, a classical explanation,
then chances are the phenomena that you're observing
don't let you do anything that classical mechanics
wouldn't let you do.
Another way of saying it is that if
you see phenomena that don't have a classical
explanation,
you may you may be able to do
things that you literally would not be able
to do under the laws of classical mechanics.
And the quintessential
example of this would be quantum computing,
cryptography, and,
information processing. They are aspects of
this science which will be impacting on people's
lives. But it to a certain extent,
they could live their lives without ever knowing
that quantum was involved in them. Right? I
think that's fair to say in the same
sense that, you know, people use their
phones and tablets and computers without maybe appreciating
the field effect transistor and, you know, the
band structure,
behavior of electrons flowing through crystal and semiconductors.
So, yeah, maybe this
technology that we hear so much about will
just become part of the background at some
point. There's this other thing that's happening in
in in the in the world at the
moment. You may have heard of it. It's
called artificial intelligence.
And,
it that's had a, like, a huge impact.
People are talking about it on the news
in education establishments
all over the place all the time at
the moment. Do you think there will come
a time when people are talking about
quantum technologies
to that extent? Is it gonna have that
sort of impact?
I'm not great at predicting the future,
but let me I I think there are
some important differences, at least in the world
as it is today, which is that to
some extent,
quantum computing
may not look like a real game changer.
I mean, maybe I have this wrong. So
quantum computing, first of all, is not, like,
my area of expertise.
But
as I understand it, you know, it offers
big speed ups around certain computational tasks.
And, you know, our society is built on
the assumption that computational tasks will gradually be
sped up over the years, right, whether it's
Moore's law or whatever.
AI, I think, is different
in that it has really revolutionized
the way that people think
of what computers can do. I mean, at
some level, it is still just about better
algorithms and hardware
and conventional speeding up. But I think AI
is really,
a shift in,
what computers can actually do in terms of
mimicking human beings, in terms of producing content
that seems original
in a way that quantum computing is sort
of maybe in some ways just a a
technique for keeping Moore's law going.
As I say, Jack Harris is 1 of
the organizers of Helgoland twenty twenty five, and
I wondered what he was most excited about
at the workshop. There are 2 parts. 1
is just a story.
So, like, every community,
every kind of group of people,
that's united by something is probably united by
stories.
And,
in science, we're united by ideas and goals
and beliefs,
maybe mostly.
But in addition to that, there are, you
know, a handful of stories. The apple falling
on Isaac Newton's head is a story.
And,
1 of the stories,
which is, you know, part
folk tale, part myth, part actual history, some
kind of blend of that. But, 1 of
the stories in our community is that,
you know, it was clear by
'19 o 05/00, '19 o 09/00 that something
very deep was going on,
that we didn't that wasn't understood. And Niels
Bohr led the way in starting to puzzle
that out. But,
for twenty or so years, there were ideas,
but not like a firm mathematical
theory.
And
the full history, which is, you know, at
least partially true, is that there was this
promising young graduate student who had terrible allergies
and asked his adviser if he could go
to the kind of 1 place in Germany
that was free of pollen.
And this is Werner Heisenberg, and this is
1925.
And in the 3 that he was there,
he made,
you know, in a nutshell, he invented quantum
mechanics, and there should be finger quotes around
that. But, you know, he made a major
breakthrough. It took a big leap. It was
kind
of a watershed or the watershed event.
And
the idea that,
there's something very romantic about this. Like, this
could be in a Mary Shelley novel. Right?
Somebody
disappears to this remote,
island in the middle of the North Sea
and, you know, watching the sunrise
over the
red,
bluffs,
you know, has this brilliant flash of
insight.
It's not I don't think the real history
is exactly that simple, but this is a
very compelling story.
And it's very compelling that, like, the topic
of our
fascination
has a place and a time,
like, a an actual,
you know, clearly defined
quantized
discrete place in Ireland
and a clearly
defined moment, you know,
That's that's just kind of, kind of a
cool
sort of a story to have,
as part of the fabric of a community.
I I love it particularly as a story
because I read a book about it,
whilst I was on a small island. In
which island? It's Lundy Island. Yeah. Oh, and
yeah. I know. Off the course off the
coast of sort of Cornwall and Wales. Yes.
Exactly. That's I've had a great,
okay. So the other for more personal side
of this is, like, I have a little
bit of a fascination with islands.
So, like, I have looked into going to
Lundy and not quite made it. Oh, you
should. Lundy's amazing. I'm very envious.
I grew up on an island.
Did you? Which 1?
Yeah. On, the island of Martha's Vineyard.
Ah. It goes to Massachusetts in The US.
Yeah. I you're excited about the the the
the location as well then, are you? Oh,
a %. Yeah. So as I mentioned, I
grew up on an island, and I think,
eventually leaving the island and coming to the
mainland, It
is like a sort of,
I think, you know, islands are a little
bit special. Like, the way that
your world view is
when there's
a border. Like, there's an end to your
world. And it's not sort of gradual, like
you drive down the highway a little further
and it's some other time. No. It's like
you're on or you're off.
This yeah. I think this shapes people's thinking
a little bit.
So it's it's a folktale, but also you
like to believe it because you think it's
true.
Well, that's the point of folktales. Right?
They're,
they have some literal truth, maybe a lot,
maybe a little, maybe a medium amount. And
they have also deeper truths,
which are sort of like, how would we
like to think about ourselves? What do we
value?
And,
yeah, that's what makes a folktale a good
folktale.
Fair enough. What what are you looking forward
to from the conversations that are gonna take
place there? Oh, so,
the principle of sort of organizing
that was done. So there are 4 of
us who did the organizing.
There's me. There's Chaslav Bruckner at Vienna,
Florian Marquardt
at the Max Planck Institute in Erlangen, and
Steve Girvin,
who's also here at Yale. And I think
the motivating like, we we talked this through
many different ways, and I I think 1
of the motivating principles was that,
a hundred years on,
there are, like, a gazillion things. Everything is
involves quantum mechanics to some extent. Like, we
could be talking about particle physics or
many body condensed matter physics or chemistry or
material science. But if you think about sort
of what was in the minds of the
founders,
in those years and shortly afterwards and sort
of
what those thoughts would connect with today.
It seems that there are really 2
amazingly
different
components to that. And,
but that they
even though they have sometimes been very much
separated out, they really have a lot to
say to each other, which are the same
which are foundational questions. Like, what is,
what is causation? What is cause and effect?
What is matter? What are the physical properties
that entities can possess and how do they
possess it?
And then
how do, like, those ideas in particular end
up getting applied?
So to build a quantum computer, which sounds
like very to some people, would be sort
of technical in engineering. It's a computer you
build it. It does the things you want.
But to make a quantum computer work, you
really have to,
absorb
a lot of the foundation's
topics. You really have to understand, you know,
what is a measurement, how do measurements
impact things, what kinds of information,
you know, alters the way a system is
going to behave.
So we're at this point where real world
practical
things like computing, like code breaking,
like detecting signals,
our ability to do that hinges on our
ability to understand
the foundational questions about quantum mechanics.
And so the scientific goal of the workshop
is to kind of bring those 2,
world views together.
And it's not that
they aren't already together, but it's sort of
to enforce that or to underscore that. I
know. Is is there gonna be stories on
the island? Is it all gonna be science
focused, or are you gonna be telling the
history as well?
Okay. So there are there's 1 session.
In fact, the first very first session, the
kickoff session is
sort of history oriented.
So there are 3 folks all with, you
know, very serious science training and background, but
who have a substantial interest in the history,
who are kicking off. 1 is,
Douglas Stone,
who is a
physics PhD and professor of applied physics here
at Yale University and an expert in laser
physics and musoscopic electronics,
but also,
has a serious history,
training. Serious training as a historian and wrote
an amazing
history of Einstein's work on quantum mechanics,
which will correct
huge misconceptions.
So if you were raised as I was
to believe that, like, Einstein never really understood
quantum mechanics, didn't like it, it was all
sort of icky to him,
and he was kind of a fuddy duddy
and got it wrong. No. This is completely
incorrect. In fact, like, what historians, I think,
knew, but what Doug explains really wonderfully in
this book, which is called Einstein and the
Quantum.
In fact, it's the opposite.
Einstein figured out almost all of the crazy
stuff about quantum mechanics before everybody else. He
understood that randomness was going to be fundamental.
He understood that entanglement was key,
you know, a a lot of the things
that we consider weirdest about quantum mechanics. And
it's true he didn't like it, but he
was pointing it out to many of the
founders.
He developed maybe 1 reason he doesn't give
as much credit is that he developed it
really in the context of thermodynamics
and statistical mechanics
rather than an equation of motion.
But so, anyway, that's that's 1 talk. Another
talk is by Elise Kroll,
who's actually in the philosophy department at, NYU.
But she is an expert in the history
of the development
of thoughts about quantum mechanics and particularly about
the role played by Greta Herman,
and other folks who,
sort of realized that some of the initial
skepticism,
people like John Von Neumann towards, you know,
other interpretations of quantum mechanics was maybe,
not on such firm grounds.
And then Philip Ball,
who is
widely known as a writer of science and
stuff, but is a physics
PhD.
And, yeah, is gonna talk about,
some of the historical
context for how Heisenberg and Pauli and folks
in our community were thinking about things in
the run up to 1925.
Amazing. You're making me even more sad that
I'm not gonna be there now, which is
Okay. Well Right. But it's gonna be happening
for everybody who's listening because nobody else can
go. Right? It's full. It's it it's full.
It's not you know, people do sometimes cancel,
and we would love to have it be,
like, you know, in putting the program together,
I think the number 1 thing that struck
us was that, you know, you could fill
up 2 or 3 or 4 of these
programs with,
you know, incredibly high level
speakers who would be wonderful to hear from.
And
it's just it's a it's a shame that
it has to be
only five days, and,
Helgoland is a really small place. It is
1 or 2 square kilometers.
They have a tight cap. There is a
little conference center there, but it has a
very tight cap on how many people can
come. So,
it's possible we'll have cancellations and the odd
slot will open up, but, yeah, it's pretty
much full.
Okay. Well,
better people than me should have their slots.
A lot of people than me are listening.
There should be a very wide range of
people. Like, the hope is that there are
surprises and connections that nobody would have would
have put to watch. So Oh, it's a
lovely thing. I I presumably, you've not been
there. I know you like islands, but you've
not been there before.
I'm planning to make a an an advanced
reconnoitering trip,
this spring, but it's true. I had not
yet been there.
My
it's a little weird to just schedule a
random trip to a desolate island in the
middle of the off season,
but it felt too
uncomfortable to organize a conference in a place
that I couldn't even really picture. So, yeah,
I'll make a I'll make a quick trip.
And, indeed, as you say, it will satisfy
a certain
curiosity about remote pilots. It's been wonderful working
with,
the 4 you know, having 4 co organizers.
That's been really wonderful to work with. It's
been really wonderful to have the support staff,
that have helped org you know, put things
together.
Katharina Kissner at Erlangen and Florian Carla here
at Yale.
And now I'm just looking forward to seeing
this place and meeting these people.
And, you know, I hope that people have
a good time and good conversations and ideas,
you know,
are are born.
That would be the best possible outcome. Yeah.
I wonder what if you if because you've
mentioned a few books and things, and
obviously, you've devoured quite a few on this
on this topic. Is there, are there any
that you recommend particularly to our listeners?
Sure. I mean, at the risk of betraying
my, prejudice and ignorance in an experience,
I would say I really
some books that I really loved were Philip
Ball's Beyond Weird.
A little bit more technical,
but not super technical by any means is,
Jeffrey Boob's banana
world,
Nicholas Gisan's
quantum chance.
It's older, but I will say as a
high school student,
maybe nothing inspired me as much as Roger
Penrose's
emperor's new mind. I
think if you're interested
in,
sort of, you know, quantum mechanics is mysterious
and so is the origin of universe and
the structure of matter. And at some level,
they all tie together. And in those bigger
pictures, I think Lisa Randall's books,
I think,
Brian Green's books, Neil deGrasse Tyson's,
those have all, I think, inspired people who
have,
you know, curiosity, but not, like, deep formal
training. I would also recommend that you head
on over to physicsworld.com
where you can find Robert Kreece's article, Return
to Helgoland,
celebrating one hundred years of quantum mechanics. And
since you're clearly a fan of podcasts about
physics,
I would recommend that you also head over
to the Physics World weekly podcast, which begins
the International Year of Quantum Science and Technology
by looking at quantum networks and sensors.
That along with plenty more coverage of the
twenty twenty five international year of quantum science
and technology
on physicsworld.com.
I'd like to thank Jack Harris, Natalie de
Leon, and Anna Maria Ray for talking to
me for this episode of the Physics World
Stories podcast.
And we'll be back next month when we'll
be looking
at Pele's tears,
and thank you very much for listening.