Dan: This is the quantum divide.

It's a podcast for people
curious about quantum networking.

What it means for the it industry
and what it might mean for them.

It's still early days for quantum,
but it's a very broad industry with

many different topics to understand.

The most imminent.

Our post quantum cryptography
and quantum key distribution.

Looking further ahead.

There are many academics building
ways to distribute content computers.

To leverage the power of
multiple machines over a network.

And how to manage quantum
state over that network.

Greetings I'm done home.

I'm a quantum curious technologist.

With no classical training
in quantum physics.

So basically that means.

I'll be the one asking
all the stupid questions.

For me, this podcast is a
vehicle to build my knowledge.

And I want to take you
on that journey with me.

Thankfully, I won't be producing
this podcast all on my own.

I'll be joined by my colleagues, Steve.

We want to bring you as many interesting
topics and discussions on quantum

networking that we can together.

Steve, why don't you introduce yourself?

Steve: Hello, I'm Steven dmo,
a research scientist at Cisco.

My background is in quantum
networks and communication.

I'll also be asking the stupid questions.

This podcast has a twofold benefit for me.

One, to stay up to date with
the current trends in quantum

networks and communication.

And two, to improve on being able to
digest the material for the interested

listeners, thanks for joining.

Dan: Okay, for this first episode,
just a couple of minutes to talk about

the vision really for this podcast.

Quantum networking for me
is such a fascinating topic.

I guess not only because of the
sci-fi field of the technology and

the way quantum mechanics works, but
also because computer networking in

general is a passion for a long time
and I feel like I'm coming home to

it, having been away for some time.

Albeit on a slightly alien planet.

So now onto the goal of this
podcast is to slowly educate

myself and you on everything that's
happening in quantum networking.

Initially, Steve and I will cover some
fundamentals, but when I say cover, I mean

discuss peppered with some mild confusion.

I would thank, we won't explain
the absolute basics, but we'll

start with quantum state.

We'll touch on quantum hardware for
networking, direct transmission,

entanglement, distribution, swapping,
and whatever else we come across.

We'll make sure we go into integration
with classical networking, all

the cryptography topics like Q K
D and post quantum cryptography.

But ultimately we're gonna have
some fun with this initially, and

then eventually we'll start bringing
in a wide range of experts and

dabblers to paint a broader picture.

I would say the target audience
here is anybody working in quantum,

but also anybody working in it?

Okay, Steve, let's get started.

Steve: Yeah.

So the key point of the key thing to
do when you're moving quantum stays.

Okay, let's see.

So there's two ways to do it.

Like when, if you wanna bring a qubit
from Alice to Bob over some significant

distance, then there are two ways
to do that, and that's using this

transmission over the quantum channel.

So you just take the cubit, put it into
a fiber, send the cubit through the

fiber, and then it arrives at Bob site.

The problem with that, which I,
yeah, there's some pictures there

when you can't talk about pictures.

You can't show the, you
can talk about pictures.

You can't show the pictures in a

Dan: Yeah.

Steve: Yeah.

So unfortunately, but I
can explain that more.

So the problem with this is when you
transmit a quantum state, if that quantum

state is holding valuable information
and then you send it through the fiber,

you have not much control over keeping
that quantum state in the fiber.

So the quantum state can convert,
get kicked out of the fiber,

and it'll never make it to Bob.

And if you use a lot of resources
to pair the quantum state, then

you've lost something quite valuable.

So what people propose is, instead of
sending the qubit directly through the

fiber, because as the fiber increases
in length, it gets even more hard to do.

The direct transmission is
to use quantum teleportation.

So quantum teleportation is in.

Protocol, so to say that uses
Another part of quantum is quantum

mechanics is quantum entanglement.

So instead of sending the information
containing cubics over the fiber,

what you send is something that's less
valuable is half of an E P R pair.

So that e p R pair you can
generate over and over again.

It contains no information.

It's just a renewable resource, so to say.

You can just generate it repeatedly.

It contains information and if you
lose it, it doesn't really matter,

but if it makes it to Bob's size,
so if Alison Bob share the entangled

pair, then they can send the qubit
state the important qubit state using

the entanglement without risking
the loss of that qubit so they can,

Dan: Yeah, let me lemme take
a step back for a second.

First of all, the approach is
sending Quantum State over the

Quantum Channel using Photons.

How is, how, just for somebody that
knows about traditional networking

and optics, how is that different
to using light to carry traffic?

My understanding is that it's actually a
case of sending one photon at a time.

Is that right?

Steve: Yes, correct.

So when you send a classical
message, the intensity of those

photons, which means the quantity
of those photons, It is just higher.

When you go to the quantum level,
it's basically just filtering out all

of sorry, all the additional photons
until you're left with one, and that

photon will hold the quantum state.

it's, that's, there's a lot
of similarities with classical

communication and quantum communication
using photons fiber optics.

It's more or less.

The challenge of getting the
photons across the channel is

much harder in quantum because
you just have that one chance.

If that one photon and all the information
is in that one photon, but when you're

sending a zero state or one state
classically, you essentially just turn

on the intensity, make it high enough,
it can make it across the fiber.

At least some of the photons
will make it to the fiber.

And there's multiple copies of the
same state where in the quantum

case, you don't have that ability.

You have one chance.

Dan: And that's why they say The
sending the state is very lossy, right?

It's very lossy.

But because you've got the traditional
things like dispersion of lighting

and perhaps the distance the quality
of , and power of the optics and so

on, all of those things, which once a
link is tuned correctly in traditional

networking is sufficient enough to
send up to, 1, 10, 1400, whatever.

But so there is no way to try and
optimize that really, because you

have to send one at a time and have
a detective that's receiving the

same stream in the right order at.

Steve: Exactly.

So there's some exceptions.

There's some schemes to what they call a
quantum amplifier, but in general For an

arbitrary qubit, you can copy it and you
can't make any repetition of the state.

So you get one chance and that's all it.

If it's lost.

You can't recover it.

You can, you basically have to restart
from the beginning, so that's the problem.

But yeah, in terms of the classical
communication, you just, you have

much more power to work with.

You have repetition, you have copying,
you have much more to get that.

Information from point A to point B.

Dan: What would be the benefit of
the approach of using sending the

state over the quantum channel?

Steve: Sending the state directly over
the quantum channel is a lot easier than

establishing entangled pairs between
distancing parties, be mainly because

there's no quantum memory at the moment.

There exists some quantum memories.

They're not at the moment good
enough to do quantum teleportation.

In the lab, there's been demonstrations
of quantum teleportation, but in the

lab setting you have a lot more control
over what's happening in the network.

But yeah, that's the advantage
of using direct transmission is

you don't need quantum memories
and you don't need to establish

entangled pairs with high fidelity.

Those are easier to do sometimes,
like so distance in when it comes to

long distance, you have no option.

You have to use some form of
teleportation or quantum or repeater.

So for short distances, probably
direct transmission could, especially

for things like Q K D, quantum P
distribution, it's probably makes more

sense just to use direct transmission.

But if you're doing something like
distribute a quantum computing, then yeah.

I think I got a little
bit off topic there.

Dan: It's easily done.

Done.

Steve: why?

Why one or the other?

So direct transmission is
simpler to do in general.

Although you can't, it
has the finite distance.

If you want to exceed the finite
distance, you have no choice but use

quantum teleportation, at least in
the early stages of quantum networks.

Dan: okay.

So I'm still sticking on number one here.

Trying to take it slowly.

Sending the state over the quantum
channel, you would be sending qubits

with particular are they in a super
position as they go across the link

or are they sent with a particular
state to be read via the end?

Steve: So it depends on the
protocol that you're running.

So in general, the quantum state is
in any state, any superposition state.

It could be completely, it's
completely up to the protocol.

Yes, it could be in a super position,
but if you're doing something like

Q K D, okay, some of the states
are not in a super position,

but some of them are, depends.

There's so many factors, but in general
you can't make any assumption of what,

what's on, what's contained in that qubit.

So I would say yes, it's always
in a super position state,

cuz that's the safe assumption

Dan: So with Q KD as an example,
what would you be sending over

the link to make that work?

Because we're not talking
about entanglement yet, are we?

So that, that's gonna be a different
set of photos to be sent over the link.

So if you're not doing
entanglement what is it that you

would want send over the link?

Steve: So in the Q K D case, that's
why I like Q KD so much is because

it's like a stepping stone application.

It's not such an intense
application that we can't do it yet.

We definitely can do it now, but what's
contained in the QBI is classical

information encoded into the qubit.

So that means, it means
it's still a quantum state.

It's still a quantum piece of
information, but encoding it is

more it's almost a binary state.

You just have to perform binary encoding.

That kind of simplifies the encoding
process and the decoding process

because you can use things like a beam
splitter, which can direct the zero

state or the one state accordingly.

But what happens is in Q kd, especially
like BBB 84 for example, is the

simplest example to use, I think, is
you polarize the light in the one zero

state or you polarize in a horizontal
basis, which is the plus minus So it's

just using a superposition state or
a classical state, and you transmit

classical information in that way.

Dan: Okay.

Does it give you more options to encode
things in less packets or something?

Because you have more different things
you can represent on a single qubit.

Steve: And Q K D is
still representing bits.

So each photon contains one You
can't exceed one bit per qit.

That's like a Some capacity,
some theoretical capacity of much

information can encode and decode.

On one qubit, you can put infinite
amount of information on the qubit by

encoding, it's a completely continuous
block sphere, for example, but

extracting the information with one
qubit, you can't ex exceed one bit.

Dan: Yeah, that's a good point.

So my understanding about the blood sphere
is it's it's the wave function, right?

Which will collapse when when it's.

Observed into one particular state.

So how could you carry, maybe this
is a tangent, but how could you carry

infinite information if actually when you
look at it, it's only gonna be one bit?

Steve: It's, yeah, that's, you
could put, yeah, that's the thing.

Like for example, let's say you'd
have a thousand bits of information.

That thousand bits of information
can be put finite, decimal

number and then the blocks space,
continuous sphere as just a degree.

You can think of it as just pointing
in a globe or something, in a sphere.

So you can make that infinitely
precise and you can put the

information into that sphere.

yeah, I see you mean like the
information is physically there,

but getting it out is not possible.

And that's why like the
decoding is important.

You can't extract that information out.

So that's the problem.

It's, yeah.

So it is, it's, it depends
how you look at it.

So the information is physically
there, it out, you can't get it.

It's just, it's gone.

Dan: Okay.

I think

Steve: So you can encode it.

but you

Dan: I think I'm confused enough now
to to probably move on to the next one

before it gets even worse.

Quantum entanglement and teleportation.

I know that teleportation is
not like the traditional kind

of Star Trek type teleportation.

And what we're doing here is splitting
entangled pairs of photons, and

these entangled pairs are entangled
in such a way that an action on one.

results in, in same behavior in the
other because they are connected

through the wave function somehow.

The wave function of the universe

Steve: I think so this
wave function observation.

So when I hear wave function, I
think of quantum mechanics and

I think of the short equation.

And the short equation basically dictates
how the quantum state evolves with time.

When you think about quantum
computing, quantum communication,

generally you don't.

Want things to evolve with time, you want
them to evolve after you operate them.

So I like the connection between
wave function and block sphere wave

function would dictate how if you
take the system, you put it into an

environment and then you just observe it.

The wave function will determine how
that system evolves with Tide, with

respect to the environment that it's in.

So you can imagine, let's say
you take a qubit, You prepared in

a state, then you put it into a
magnetic field and then you watch it.

And how, what happens to that qubit in
the magnetic field is defined by the

wave function a particular point So
it's usually a time dependent thing.

So when I think about quantum
communication, I think we don't

want that quad of state to change.

When you encode something into the
qubit, you want it to stay that

way until it's recovered by Bob
or else the information changes.

Basically the, you get
noise in your decoding.

So I always try to picture things
in terms of just fixed Noiseless,

evolution of quantum states,
they only evolve when we a we.

Put them in through shine light at them
or somehow interact with the cubit.

That's the only time it changes.

So it's almost not time dependent.

It's like discrete, time dependent.

I dunno, but you only change when it only
changes state when we do something to it.

So that's I think, an easier
yeah, You have the cubit, it's

fixed until you operate on it.

Dan: Fun.

Steve: So it's entanglement
is, like you said, they're

correlated to photons, to cubits.

They're correlated in a way that if
you measure one of them, then there's

something happens to the other one.

Operating on them alone is not
enough to influence the other.

You have to make a measurement, and
when you measure, then it collapses

the quantum state into a subset of
the states and those subset states.

Actually influence, it forces the
other part of the entanglement to

collapse into one of those states?

Dan: Always identical.

The states, which are a
result after the measurement.

Steve: No, not always.

So there's what we call
maximally entangled states.

Maximally entangled means that
they're either completely correlated,

which means they're exactly the same
or they're anti-correlated, which

means they're exactly the opposite.

But it's not always necessary to
have maximally, entangle, state,

and therefore they don't always
have to be the same output.

And they only also don't have
to have the same patterns.

They don't have to be like
completely correlated or completely.

Antico is something in the middle too.

Dan: So how do you want to explain
the quantum entanglement in

your yeah, I, I know we're both
looking at a circuit diagram here.

Do you wanna describe that or yeah.

Steve: Yeah, so usually what we think
about when we talk about Quan protocols,

you usually want to use the maximally
entangled states that are either

completely correlated or anti-correlated.

The protocols can be modified accordingly.

It's not so important what flavor
they have, but usually we're talking

about the maximally entangled state,
which is in the zero 11 bell state.

That means like if you measure zero
on one, you'll get zero on the other.

For sure.

If on one, you get one on the other side
as well, like completely deterministically

after the measurement has been made.

And those are easy to work
with because then you can write

the math down much simpler.

And thinking about that perfect
correlation is a lot easier to use.

So in quantum teleportation,
we assume that it's that exact

state, the 0 0 1 1 state.

Yeah, so Quad teleportation uses that
state, and at least in principle,

in practice things are different.

You have noise and you somehow,
when you're distributing bell pairs,

you don't always get that state.

You could distribute a bell pair but not
get the 0 0 1 1 state anyways, divergent.

But in the circuit diagram, we are looking
at, we have a arbitrary quantum state.

And then we assume that there's this
bell pair that's already established

between the two communicating parties.

Then what we have, so that means
that Alice, who is descending, the

qubit, has her quantum state plus
one additional state, which is her

of the total entanglement state.

So it's an additional qubit.

So she has two cubits in total,
one containing her information

and one half of an entangled pair.

On Bob's side, he has the other half of
the entangled pair and he doesn't need

to So he only interacts with that qubit
when Alice specifies what to do with it.

So on Alice's side, she takes her qubit
and she performs a certain operation.

And that's a two qubit operation where
she interacts her information containing

qubit with her half of the entangled pair.

And then she has to perform
a measurement on her side.

Actually, she measures
both of those qu bits.

And that's because when you make the
measurement, then the system collapses.

Only when you make the measurement
does the system collapse,

and then she sends those.

So that's what Alice does.

And then now she has, because
she measured two qubits, she

has two bits of information and
those two bits of information she

has to classically send to Bob.

So that disappear classical transmission.

And Bob receives the two bits of
information and he can now do something

on his half of the entangled state,
which is still in a quantum state.

It's not measured.

He has to hold onto it in some memory.

And with those two bits of information, he
applies what we call like a corrections,

some kind of quantum correction.

And what happens after he applies
that correction is his half of the

entanglement is exactly in the state.

Of the information containing qubit
that Alice had on her side and that's

the quantum teleportation protocol.

So now he has a qubit.

It's not measured, he just
performs certain operations on it.

And now what information that qubit holds
is exactly the information that was held

by Alice's side, by Alice's information
contained And very importantly is Alice

no longer has access to any of her qubits.

They're gone.

Or at least the information
inside those cubits is gone.

So It's a physical, it's not a movement.

It's a transfer of information.

So the information is lost on Alice's
side, and it exists on Bob's side.

Dan: Yeah, it's fascinating.

It really is.

So you've got the no cloning, the,

Is what you're referring to there.

But the fact that you can essentially
send information across the optical link

without needing to send the information
across the optical link is wild.

It really is.

Steve: One thing though, is
there is one transmission made.

It's a classical transmission.

Like that's, I know what you mean.

Like it's a fascinating for sure,
you're sending quantum information.

Using classical transmission
that's more precise.

I'd say it's, but you still
have to make a transmission.

You still need some connection
between Alice and Bob.

Dan: Sure.

But the information that's encoded
across the entangled pair is not sent

across the classical connection, is

it?

It's more like a
controlled, the way I see.

It's like a controlled layer.

Steve: that's so that we
would rely on this scheme for.

Transmitting quantum information over
long distances simply because it's too

lossy to send the information containing
cubits directly through the fiber.

Especially when that cubit
is valuable, then it's really

costly to lose that qubit.

Dan: Yeah, and you're losing out
on our whole potential security.

Opportunity here, right?

And that, that the information that's
sent cross entangled pairs cannot

be captured in any way on route.

And I know that obviously we can't
break the laws of physics, so you can't

send it faster than speed of light.

But will it mean potentially that
in very big networks that there will

be quite large speed improvements
in the way data can be transmitted?

Because I'm assuming that the
entanglement that this, it's an instant.

When Bob looks at and acts on the,
on his entangled part of the pair

up there that he gets an instant
reaction from it to reveal the

same information that Alice has.

And that does sound like it's
faster than the speed of light, but

it's not because it's, the control
traffic has to be sent in advance.

Steve: Yeah, exactly.

So because those two bits of
classical information have to be

sent, over, using light speed.

There's no instant, there's an
instantaneous reaction to the

entangle pair, but Bob has no
idea that Alice measured anything

when Bob measures his qubit.

he doesn't know Alice measured hers as
well, there's nothing saying that his

qubit They he'll know that whatever
he measures Alice will have measured,

but that doesn't mean there's any
information encoded in that qubit.

Before any collapse has been
made, any been made is random

output 50 50 in a bell state.

So Bob will measure, he'll see a zero, and
he'll see a one with equal probability.

Alice is guaranteed to see the same
thing, but that just means we both

flip the coin and we saw the same
that's not message transmission.

So there's no Just because we both
have the same random output doesn't

mean I communicated anything to you.

But what's, what could be done is
you can use that as a it's not like

we can have faster communication,
but we can have faster strategizing.

So if we want to play a game together,
for example, and you say, I'll act, if

I measure zero, I'll act in this way.

And if you measure zero, you act in
that way and we can actually play.

We can actually improve in some
schemes, in some games using strategies.

And this is actually more interesting
to me that we can behave in synchronous

without communicating at all.

You can also do this classically,
but in some cases you can modify the

entanglement and actually improve on
the winning probability of some games.

So let me try to rephrase that so you
can imagine, let's say we're playing.

Strategy game.

We both are holding a coin.

So I flip a coin and I get heads and I
say, I'll move left if I and I'll move.

If I get tails and you do the same, or
maybe you do the opposite, and this way

we try to avoid collisions or something.

I don't know.

And you could do that classically,
and we don't have to communicate,

but if we have entanglement, we could
coordinate ourselves, say, I'll measure

my qubit, and you measure your qubit.

Or I'll apply as an operation on my cubit
and then measure it and you do the same.

In some cases you the game.

Yeah, that's not a very good But
you can play games with entanglement

and you can coordinate and win some
specific games with higher probability

than if you just had that coin,

Dan: now, whilst you are trying to explain
the interesting analogy, I am constantly

thinking about the application of this and
how it compares to classical networking.

And what, what applications are
there in classical networking

that this would either.

Improve or the equipment to, or act upon.

And I, it's difficult to think,
potentially control information

potentially decision making in the
network could use this somehow to

Who knows alter the way routing
protocols work or something.

But I would guess there's probably quite
a lot of the benefits that we don't

really know yet, or what they're gonna
be on, how this technology is gonna be

applied to changing the way information
is sent across networks and the internet.

Is there any research out there going
on at the moment that's looking at the.

The higher order applications of
this type, these types of things.

Steve: I know.

So in game theory, subset of
game theory, quantum game theory.

But going networks I know I've seen one
paper, something like five years ago

that talk about using entanglement to
manage congestion in classical networks.

And I haven't been able to find that
paper since, and I don't know if I'm

imagining it or not, but I swear I read
something about that at some point.

And it's essentially choosing paths
in a network using entanglement,

measuring the entanglement to just
make decisions on which path to take.

This way you can choose paths so that
you avoid congestion in the network.

But other than that, I haven't seen
too many results about, like thinking

about using entanglement in that way.

I know, an exhaustive list of scientific
outputs, it's, I think it's not

such a popular field at the moment.

Dan: Yeah, that's an interesting one.

This feels very top heavy too.

Put all of that type of technology
in just to optimize the routing in

that way and ensure that there's
perhaps no queuing, scheduling

happening, interfaces in the route.

But.

Steve: Maybe just one more point I
wanna make is, it's very important

to think about the things that can be
done better with quantum entanglement.

There's actually.

A lot of cases you think, okay,
we have this shared source of

randomness completely correlated.

But that doesn't mean
you have an advantage.

You can also take a ran pseudo
random number generator and plug

in the same seed, and we'll have
the correlated outputs as well.

You don't need entanglement to
have correlated random outputs.

So this is a very fine line
between quantum advantage and

not, and I think this also is why
it's not such a popular field.

It's very hard to find that advantage.

Anyway,

Dan: Yeah, no, this is gonna be
interesting, I think in this podcast this

part and one that we record going forward.

Ultimately we've we spent most of this
time talking about the very fundamentals

of how quantum states can be transferred.

But, there are many different
applications of that potentially,

and there's lots of different aspects
of it, such as the transmitters, the

receivers quantum memory you mentioned.

And the fact that needing to
use repeaters of some kind to.

Send quantum information.

I read something that that about a an
experiment where it actually proved

that quantum repeaters can work.

Something, I'm sorry, I don't have the
actual reference to me, but I'll put

it in the pod notes if I get a chance.

Yeah, and we've touched on the kind
of issues with direct transmission.

The fact that the links are very lossy.

Fiber optics obviously gives you a limited
amount of distance and obviously it's a

bit different when we get into space free
space networks like satellites and so on.

But perhaps that's, that's
definitely a topic for another time.

Is there anything else that you think
we need to add when it comes to the

fundamentals of how Quantum state is.

Transferred, I mean without getting
too much data into the physics.

Steve: I think that's mostly the.

That's the core of it, at least direct
transmission entanglement sw sorry.

Oh yeah, there's, I guess there's
one part yeah, if we go into the more

depths as like the quantum repeater
and what does the quantum repeater do?

That would be one part to touch on, I
think, because that's also, it's just

because you have the ability to do
teleportation doesn't mean you exceed

the limitations of fiber communication.

So you need, still need a repeater,
but teleportation basically enables

that repeater at least what we
call the first generation repeater.

Dan: Yeah, that's right.

Repeat is in the quantum world, are
not the same as fire or something that

is Receiving packets, deconstructing
them or reconstructing them or anything

because it, first of all, it can't
interfere with the photons and the qubits.

So it's using, these things
are using deportation, right?

To my understanding is to receive state
of incoming in cubics and transfer them

to different entangled pairs so that the
stake can then be passed on with that.

Let you know that's my
super high level view, but.

Steve: Yeah.

No, that's a good in, that's
a good interpretation.

It's simply just, it's exactly that.

Just teleportation chain, essentially.

Teleport, teleport, teleport.

And then eventually it
arrives where it needs to go.

But each of those teleportation
requires point to point

entanglement at least in some cases.

It depends how you're implementing
the swapping procedure.

But yeah, you could in theory
do it as a teleportation chain

or you can do this inte ent,
integrous swapping procedure that.

At the end of the procedure, the only, the
endpoints of the chain have entanglement

then you make teleportation directly.

So there's two ways to do it
somehow, but that's mostly it.

Dan: Yeah we're looking quite
forward into the future in being

able to do this type of thing.

Like I said I've saw an experiment
recently where they had enabled this

teleportation using a repeater, but
I guess that was over two links and

obviously in a very in a lab environment
basically, and using technology that's

that's built specifically for that task.

We're gonna be years and decades away
even, but for this to be applicable

in the real world, and I expect these
types of devices will end up looking

like perhaps transceivers or optics
that go in forwarding and information

management note of some kind.

Or you could call them routers,
but ultimately it depends on.

What is this?

They're doing

Steve: But yeah, no, it's, it makes sense.

Yeah.

These things are still completely,
it's mostly academic work.

I think we're some time away from it
deployed in practice, although it's

not, they're not stopping people though.

There's people putting these technologies
into metropolitan scale networks.

It's a push, like a lot of people thinking
forwardly, but also some groundwork to

Dan: Yeah, maybe just a couple of minutes
on, on, on tackling in the real world.

I'm aware of a couple of.

Partnerships that Cisco has with some
universities where some of these kind

of concepts are being tested in the
real world across metropolitan networks.

I'm aware of one in
Cambridge, for example.

Perhaps we can talk about
that in a separate call.

Are there any of us that you'd like
to highlight where quantum networking

is being tested in the real world,

and if So , which concepts that
we touched on today are relevant?

Steve: Yeah.

So generally these, what deployed
into metropolitan scales, either

Q K D as most commonly Q kd.

Actually, there hasn't really been a.

Any entanglement distribution networks
so far until recently, actually,

so the q kd ones are interesting
because it's a commercial product.

People want security and so these
are but , it's getting old, it's

not really, it's all the term.

in the young stage of quantum
networks, it's been done a few

times now and we've seen it.

It gets more advanced every
time, higher communication rates.

But for the first time, I think this
year we've seen a metropolitan scale

entanglement distribution network.

that's something to look at, I think.

And that's what deployed in New York.

I don't know much about it actually.

I need to do my own reading, but
I saw the highlights at least.

And so this network is different
because it's not doing Q K D, but it's

distributing entanglement as far as

Dan: So yeah, the thing with,
I'm translating what you said

there to, to me Q KD is not that
interesting to some people in the

field anymore because it's maturing.

You say That's right.

Obviously it's incredibly exciting in
the way that it's gonna be changing the

way we do cryptography and it's gonna
be important for ensuring we've got

quantum safe cryptography going forward.

Steve: Yeah, I think in general,
it's one of the, it's the most

mature, as you said, the most
mature helping and co communication.

It's gone through quite a few iterations,
definitely seen a lot of varieties of it.

So not only through fiber optics,
also through space communication near

distance, long distance, different
types of protocols, different designs

for the network for the Q K D.

Also, the classical parts have been
well established now, so not only

do you need to transmit the key.

Using the quantum states, but then you
need to extract the key efficiently

and then store the key efficiently.

So not only do you have, you
still have a key, you need to

keep that safe classically too.

So all the things like surrounding Q
K D have been not well established,

but they're much, much further
established than any other

quantum application for networks.

Yeah, I think yeah, I think Q KD is
a topic on, it's only, it's another,

Dan: Oh yes.

Okay.

Thank you Steve.

I think we'll wrap it up there.

There's just so many topics that we
could go into and I think we're gonna

have to end up recording quite a
few of these to to do them justice.

So thanks very much and
I'll speak to you next time.

Steve: My pleasure.

Dan: I'd like to take this moment to
thank you for listening to the podcast.

Quantum networking is such a broad domain
especially considering the breadth of

quantum physics and quantum computing all
as an undercurrent easily to get sucked

into So much is still in the research
realm which can make it really tough for

a curious it guy to know where to start.

So hit subscribe or follow me on your
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in the world of quantum networking.

Spread the word.

It would really help us out.