Dan: Okay, welcome back
to The Quantum Divide.

This week we've got a very exciting guest,
but before, before we introduce him I

just want to say welcome back, Steve.

It's been three episodes
since since you've been away.

I've had a great great series of
conversations with Harold Olivier

from INRIA, Shreyas Ramesh from
Accenture, and Juan Moreno from AWS.

It's been pretty busy, pretty fun.

So welcome back.

Steve: Yeah, thanks a lot.

It's been a busy couple months.

I had to take a little hiatus,
but here I am back again.

Dan: Yes good man.

Okay.

Yeah, listen, before, before we start
with today's guest I want to just

tell you about a personal quantum
moment that I had, and it was actually

meeting this team that really got
me personally into pursuing more

knowledge in, in quantum technology.

It was at a Cisco Live!

Event.

And I met a company called
Quantum Optics, Jenna.

He told me all about their entanglement
based QKD and it totally blew my

mind and I love talking about that.

But that's who we're with today, so
I'm lucky very lucky to be joined by

Kevin Fuechsel from QuantumOptics Jena,
who's the CEO of QuantumOptics Jena.

Welcome, Kevin.

Kevin: Thanks a lot.

And it's a pleasure to be here
and be part of your your podcast.

So we are really happy
to have this opportunity.

And it's really a pleasure that
we bring you to the quantum side.

I love to hear your story every time.

Dan: Very good.

Yeah, great.

Listen let's start like we normally do.

Just to hear a bit about you,
how did you get into quantum?

What's your path to
becoming a CEO of a company?

And yeah, let us know how it's going.

And and and then we'll start with
a few questions and go from there.

Thanks.

Kevin: Yeah, happy to.

I probably don't have a typical
quantum career, I would say.

So I start my PhD in semiconductor
and nanostructuring technologies.

I did my.

work in photovoltaics at the beginning
and also my PhD is in this field.

After PhD, I've got the opportunity
at the Fraunhofer Institute of Applied

Optics and Precision Engineering
in Jena to work in the field of

strategy, marketing, and communication.

And in there I was also responsible
for some strategic projects and I think

it was 20 14, 20 15 when first things
of Quantum get also on our radar.

We, yeah we thought about what
can we do in this regards.

We had a first project with
a team of the ECOC in Vienna.

At this time, 2015 which was dealing with
an entanglement photon pair source which

should be space proofed at this point.

So also our co founder Oliver or my co
founder Oliver de Vries who's now a CTO

was heavily involved in this project.

And there we get the first.

Let's say connections to to
quantum to all the stuff around

quantum communication, especially.

And we recognized in 2018, I think
it was that the quantum market is

maybe ready to have another startup.

And we believe that we
could play a role there.

And so we decided to to think about.

It takes us two years after this first
thoughts to really found the company.

So in 2020 we decided to to move on.

So we in October we found the company,
um, also in 2020, we start discussing

our idea with first investors because
we we know it's a, it would be a, it

will be a deep tech company where you
need some investment to really move on.

So typically you have to decide at
the beginning, if you want to do

it, I'd say with your own money.

So in in 2020 we we decided to to move on.

Getting investors on board the
process there was quite fast.

So it just takes us three months
to convince investors to to get on

board and run the company with us.

The good thing was with my activities
in in the strategy field also had the

opportunity to coach some startups
and do some innovation process stuff.

This helps a lot if you then do this.

By your own, so you know all the
let's say how to create a business

model this business model, a canvas
stuff, this value proposition stuff.

And we've done this let's say a
year before we found the company

and get also the idea of what a
potential product has to look like.

Because at the institute itself,
we just had the entangled source.

So this was the product what we are.

Taking out of the, or not taking
out what the experience we

had as we started the company.

And based on this especially in the first
year, we built up everything around.

But I guess we will come to
this in the later questions.

Dan: Yeah, before Steve chimes in,
I know he's champing at the bit.

I just wanted to ask you, you
started in semiconductors, but

then you went into photonics.

How was that transition
or was it just natural?

Because it's all part of

Kevin: Yeah.

Dan: Atomic and photonic

Kevin: Yeah.

If you work in photoable tanks or
solar cells, whatever technologies

it's every time a combination of
semiconductor physics photonics.

And I work in the, in a department
which deals with optical coatings.

So typically it is, let's say the
interconnection between the real

world and the devices, structuring or
designing interfaces, which guide light

to the thing or to the parts of devices
where things happen so electrically.

So this was the main.

Issue there.

So we, it was also a fun project.

It was it has some relations
with nanostructured silicon.

So there was also some kind of quantum,
because you can do, you can structure

silicon in a way that it transits from a.

Indirect semiconductor to
a direct semiconductor.

If you go to, let's say dimensions
of nanometers or less than a

nanometer this is also fun.

So you get some experience in all those
quantum effects if you working in physics.

In general, I would say so, it's
at least from, for now, it's still

every time a little bit spooky if you
think about this entanglement stuff.

It's something you cannot.

Imagine from your real life experience.

So it's some it every time is really
fun to explain it especially to people

who are not in this mathematical
world or in the physics world.

And Because then you see directions
and this, that this quantum revolution,

which we are in now is really
something which can change paradigms.

And it can change also how we use
technologies because think about it.

We are now at the point where
we can control or where we use.

Single photons where we use
qubits was over the elementary

particles, so this is exciting.

I would say,

Steve: Yeah, I think especially, it's
not that easy to explain to people

how entanglement works and what's
so fascinating about it, especially

if you can't use mathematics or, the
physical properties to explain it.

But it's very exciting times, probably
10 years ago, no one would imagine

we have an ecosystem of quantum
computing, quantum communication

which leads me to the question next,
I guess the first question from my

side, it's not a technical question,
but it's more on the business side.

So a lot of the startup companies
coming from UK, US, but you sense

that Germany is a little slower.

I wonder what your impression is there,
how is it getting investment in Germany,

setting up the company in Germany?

I know you've spread out by now to other
countries, but it started in Germany.

So maybe you have some help,
some advice for others trying to

navigate the ecosystem of Germany.

Kevin: A very good question.

And also I would say an observation.

So I would say the German culture is not
let's say do well known for a startup

mentality, but I'm happy that we have.

Yeah.

At least some startups running also
in Germany or starting in Germany.

My suggestion for anybody around who
wants to do a startup, do it, just do it.

Do me a favor.

Just do it.

It's not too, so complicated.

It's a lot of fun.

And even if you, if it doesn't succeed
you will learn so many things for getting

back to industry or doing other stuff.

That's really a value which you you
will get out of this process at the end.

I think our learning was
especially for seed rounds.

It's not too complicated
to get funding in Germany.

So you have so many partners and so
many funding opportunities right now.

You can start with
typically BMBF projects.

There is this EXIST fund.

I would say, we just say try to ensure
us the transit from academia to to a

company in a, let's say A longer way,
I would say but you also have investors

who would do a great seed investments.

We have our seed investors one from
one is the Fraunhofer tech fund.

It's a dedicated fund
for Fraunhofer startups.

Another one is the Beteiligungsmanagement
Thuringia or short BMT, which is a

fund especially for our local area.

And we have a third party or third
fund ELAS Technologie Investment.

They are private investors.

I know them personally a long
term and I could convince them

that we are a cool startup.

We have happy to have them on board.

But so as we have the seed round, we
have to say no to other investors.

So there are also plenty of other.

Potential investors.

The High Tech Grunderfonds Germany.

HTGF is available which has also
some great startups in the portfolio.

So if you want to do this just
go, you don't have to be shy.

So just go out speak
to investors to funds.

They are very open.

If they believe you are a great team and
you have a unique technology, I think

you will get Your round closed very soon.

This is not the challenge I
would say, or it's not the the

challenge, you can solve this.

Dan: Fascinating.

Let's give you the stage now to talk
about I suppose actually I'm going

to cheat and give you two questions.

First of all, I'm interested
about Jena in Germany.

So why Jena?

I've just Googled it quickly.

other search engines are available.

And I read that it's a major
center for optical and precision

instruments and glass products.

Is it, does that have anything
to do with why you're in Jena?

And then if you could give us your
overview of what it is your company is

doing when it comes to quantum networking.

I know you have a number of different
products and different industry

verticals, and maybe go to market.

So please walk us through all of that.

We'd love to hear it.

Kevin: yeah, sure.

Yeah.

Why, obviously we, I study physics
and, also Oliver studied here, so

we have also our families live in,
but that was not the main driver.

The main driver was really as well
known for photonics and optics.

So we have, I think 200 years of
history in optics in, in, so it's

the birthplace of Carl Zeiss.

The company it's also the
birthplace of auto shot.

And it's an interesting story how
you, if you think about how the

companies are funded or getting
to the point where they are now.

Are we limited in time in the podcast, but
then, or can I go a little bit around this

Dan: Yeah, go for it.

Kevin: it's an interesting story,
which demonstrates how innovation

can happen, so it was a Carl Zeiss
who found his company building up

microscopes or optical instruments.

And at some point he during his
manufacturing was trial and error,

you take some lenses and you
put them together and you have

a look if it is working or not.

And he comes to the conclusion, maybe
that's not the smartest way to do things,

and he decides to go to university.

To the University of Vienna and ask a
professor there which was Ernst Abbe.

And and Abbe, hey, can you
help me with some mathematics?

Can you find some mathematics
to to actually calculate things?

Shapes of lenses, for example, or
what are the limitations of devices?

And Everybody who is involved in
photonics, who they know the upper

limits for resolutions of microscopes.

So this is the output, the basic theory.

And on the other hand he gives the
company some kind of mathematical

tools to design optical instruments.

And this was a starting of let's
say a very interesting story because

we get the work close together.

Abbe takes the lead of Zeiss
after let's say Carl Zeiss was

was not available or retired.

And he really did a lot at the say
I think at the end, more than 30,

000 people worked in Jena around
optics and photonics, which is

quite a lot if you think about a
city size of 100, 000 inhabitants.

There is a lot of competencies
around Jena in optics from optical

design to manufacturing to testing.

So all this is here and you can see this.

Why not see, but you can feel this if
you are doing physics around and doing

some networks, also networking stuff
around many, there are over a hundred

companies dealing with optics and
photonics in this area, in this local

area which gives you let's say a lot of.

Experience people.

And for us we strongly believed
in, as we found the company that

it will be a good sign if we take
the name of the city where we found

the company into our company name.

So we are really proud to have quantum
optics, because something which

which stands for competencies in
optics and photonics and To maybe get

the shift to your second question.

So for us we really, we truly
believe that the quantum technologies

will be the enabler of the future.

And we also want to be
part of that future.

And for us, it's in everything we
do it's important to to use quantum

technologies in a way that we
can create a quantum added value.

We don't want to do quantum because
quantum is fancy because we believe

that quantum will bring you some value
to products, to solutions, which you

cannot achieve with classical solutions.

This is, this we truly believe and the
first product we think is most successful.

There is a low risk of failing is in
the field of quantum communication.

Our company or we see in the
future different markets for us.

So the biggest or the most interesting
right now is quantum communication.

We also have some activities right
now in the field of quantum imaging.

And we also believe that in the
future, especially if you think about

quantum computers there might be
niches for us where we can help with

our technologies to to improve or to
enable quantum computing networks.

Let's put it this way.

So these are the three pillars for
us where we want to to do business.

But the most interesting right now
is for sure, quantum communication.

Steve: So at Quantum Optics Jena at the
moment focusing on quantum communication,

specifically in quantum key distribution.

As far as I, as far as I
know, you can expand on that.

And I'm just curious of what
differentiates your pro, your

your approach from companies
who are also performing quantum

key distribution as a product?

Kevin: Yeah.

So as you already said in the
introduction, so we believe that the

approach of entanglement is the right one
to To go for in quantum key distribution.

So for all the listeners outside, so
quantum key distribution is, it's a frames

the the concept of delivering symmetric
encryption keys to certain parties

with the help of quantum technologies.

And in our case, it means the source for
these keys is the entangled photon pair.

Source at the end, it generates and
entangled or in qubit state which

which is entangled in a way that
if you have now two Parties, let's

call them Alice and Bob, work in
the framework of the ecosystem.

And if you now send the photons to Alice
and Bob, so one to Alice, one to Bob.

And if they measure the state, or the,
let's say the state they will Let's

see, break the entanglement or the
entanglement is done at this point.

And the beauty is the measurement
results if this is really entangled

they don't have to talk about results.

They already know what the
other side will have measured.

And this gives you the
opportunity to create.

Or to distribute keys in a way that
you also will find attackers within

these the line of transmission, because
if you measure a single photon or

an entangled photon, you break the
entanglement and you cannot clone this

anymore and create the same state.

And this is the, for us, this is
the main value of this QKD approach.

You have a source of high entropy because
it's also a quantum process which we are

using to generate those qubit states.

You distribute those qubit states in a way
that you will identify any eavesdropper.

So you can make sure that the keys
you Receive at the end will be

highly secure and you can use those
keys for your data encryption.

So it's the basic approach
of of our company.

And we believe at the moment we have.

Maybe the most advanced complete
entanglement based QKD system.

There are many companies all
around doing other cool stuff.

There are CBQKD, there is DBQKD
with prepared measure approaches.

At the moment, the There is not say the
market is is in the making, I would say.

I every time tell tell others you don't
fight over the cake if it's not baken.

There is also a lot of corporations
and we have we know probably the

most companies around and discuss.

Things with them, and we will see how
this will will be in the future, or how

this will be developed in the future.

For us, we personally, or we as a
company, really believe entanglement is

a really nice approach because it has
some advantages in terms of assumptions,

especially for a quantum channel,
because we only have Two photons, and

this makes life, especially for the
security proof a little bit easier.

Steve: Like I have a
follow up question then.

So that sounds, people might
think about the system and say,

okay, entanglement distribution.

It's such a complex tool to
have or such a complex resource.

But what's the hardest part of
distributing entanglement, do you think?

Is it preparing the entanglement,
sending the entanglement over the

channel, measuring the entanglement?

What's the biggest hurdle of
sending entanglement between

devices, do you think?

Kevin: To be honest, I think we have one
of the simplest system set up you can

ever imagine in terms of a QKD devices.

So it's really just a simple
entangled photon pair source and

then those measurement devices.

So the hardest challenge for us is
it's not the physics around that

because we have, there are so many.

Papers around and so many research
groups with really cool approaches to

doing multiplexing entanglement stuff.

So this is really fun to see.

Also, the hardest part for us
was getting to system to a 24 x7.

Operation, so that you don't need
a physics PhD or backgrounds in

engineering to run the system actually.

And so the main challenges for
us were two, so one was how can

we synchronize two clocks which
are way apart in the easiest way.

And therefore we.

Yeah we, this was a hard one.

This was the first step and the
second step was if you distribute

entanglement over networks and you
don't go over real fibers those

fibers are not, they will not.

stabilize the system, or
let's put it this way.

If you have a, we take a polarization
and if you distribute a dedicated or

a special or a fixed polarization or a
fiber it will not you will not measure

this fixed polarization at the other end,
so there will be some changes and those

changes are, they happen all the time.

They depend on pressure on
temperature on whatever.

And this was the second part.

How can we compensate in a smart
way those changes in polarization?

And this takes us over a year to
develop the technologies around

to enable this at the end which
is now also the coolest thing.

For us, because we have now the tools
to really compensate for changes

and run the system in the 24 x7 way.

This is really the hard stuff.

So if you come from academia,
there are really smart people

around and they do great stuff.

But for us as company, the hard stuff
was to to find an approach or find

the solution to do this 24 x7 without.

An engineer turning things
changing parameters, et cetera,

Dan: That's fascinating, Kevin.

I'm just going to recap some of that.

And I'm also going to go back to the
hardware cause I want to go up the stack.

I think, and it sounds like the complexity
for you is around the software, the

operationalization, the simplification
of control and those types of things.

But ultimately the way the entanglement
generation works, correct me if I'm wrong,

is you have some kind of a pump photon,
which is sent into a crystal of some kind.

which then splits it into two lower
power, lower wavelength entangled

photons, which are a Bell pair.

They're an EPR pair of some kind.

That's my understanding.

And then those are sent down the two
different links to Alice and Bob.

Have I described that well enough or
is it have I missed out huge chunks?

Kevin: But the wavelength is not shorter.

It's longer to be honest.

That's the only mix up in this
case, but yeah, so the process

we are using is called SPDC.

So it stands for.

Spontaneous parametric down conversion.

It's a process which is well
known in nonlinear optics.

So if you would do some
conversion of laser light, this

is typically the way to do this.

And in our case, it means you have a pump
photo, which Has a certain possibility

or probability to be transferred into
two photons within a crystal, so it's a

very low number, which you transfer, but
the energy conservation and also momentum

conservation has to take place for sure.

But.

It can happen, and in our case to to
create an entanglement or create this

this qubit state we use a configuration
which is called cross crystal.

So now we do a quick conduct experiment.

So just imagine you have an pump
laser, which where do The oscillating

field of the wave is horizontal.

So it, it oscillates in
horizontal direction.

And it now interacts
with the first crystal.

You have a question then?

Dan: Kevin, why is it called a, why is
it called a pump photon or a pump laser?

Kevin: Oh, that's a good question.

I don't know, to be honest.

It's classical.

It pumps,

Dan: okay.

Kevin: That's now for optics

Dan: Carry on.

Kevin: You learn it during
your studies this way.

So it's every time pump photon, signal,
idler photon, but I just want to avoid

signal idler photon because it's maybe
a too specific, but yeah, so you have,

you have a laser, you just can imagine
you have a laser pointer, right?

A very sophisticated laser pointer
which shines through the crystal.

And now this this Oscillation
is horizontal, right?

It interacts with the first crystal and it
has a certain probability to arrange those

two photons, which are longer wavelengths
or so typically you can imagine, let's

say you pump with 400 and you can get
to 800 nanometer photons out of this so

now we have or we take, we have a second
crystal, which is rotated by 90 degrees.

. to the first one.

And now we have vertical
polarized lights, right?

This shine, or this goes through the
horizontal polarized or the first

crystal, because it will not interact.

Those crystals are designed
in a way that they will not

interact with with this photons.

And so now the magic happens,
or this SPDC process happens

in the second crystal.

And you have also two photons.

They are not entangled yet.

The entanglement comes into place or
this qubits generation comes into place.

If you now have a pump laser, which has a
45 degree angle to a horizontal vertical.

So it's just in the middle of this
of this, and in this case, you don't

know where the magic happens because
there's a probability of 50 percent

that this will happen in the first.

Or in the second, since there are only
two photons and there are created at the

same time, at the same space, you have
to measure that's the only way to do this.

And if you will look this on a on a
mathematical way, and then you get those

Bell state stuff and you, you see the
whole beauty but for the listeners it's.

It's this kind of simple, you just go
inside this architecture with 45 degrees.

And then the magic happens for sure.

You have to do some other stuff
to compensate for, let's say

birefringence effects, et cetera.

But this is then the, that's
where we come into play.

tHe team is really great and
they know how to do this.

And building this up that you
can distribute entanglement up

to a hundred kilometers.

Dan: Great.

Sorry, Steve.

I'm going to jump in again.

Too many questions trying
to get out of my head.

So let's talk about the other end.

You mentioned timing.

Let me start with quantum memories, right?

The way traditional networking
works is if you're sending something

over a a network and you, maybe the
applications need to wait or you have

some kind of buffer in there, right?

Which.

where you can receive information,
you can queue it somehow, and that

can happen anywhere in the network.

Now with optics, with photonic qubits,
ultimately my understanding is that

there aren't really any quantum memories
yet that can hold photons effectively.

There's a few crazy experiments
out there that I've heard about,

but it feels this is one of the
challenges you've had to solve, right?

And the challenge is that Alice and, Bob.

need to receive the photon,
photons exactly the same time.

And that's why you have...

Yeah, please correct me on this.

Kevin: No,

Dan: you have a very accurate
synchronization between Alice and Bob's

devices, so that they can perform their
measurement on the photons as they're

received to do the QKD calculation
and work out that part of the key.

Kevin: Maybe we have to to differentiate
at this point a little bit.

Quantum memories or quantum
repeaters the purpose of them is

to distribute entanglement over.

Longer distances, right?

So in our case or in our setup, we
don't need a quantum repeater or we

don't work in this scheme, so it's
really distributing two photons

to create a symmetric key on both
ends or on on entities who want to

communicate without the The repeater
stuff so far, so this is for sure.

Interesting.

There are many, uh, research
organizations investigating in

this also some first startups we
see on the horizon investigating

quantum repeaters, quantum memories.

And for those purposes yes, you need some
kind of storage or let's say longer times.

to have the photons there.

But in our case, we just
have to synchronize.

So it's a little bit easier.

We just have to synchronize two clocks
to do a coincidence measurements.

We just need to to lock
them to each other.

And as I mentioned before
so how we do this, we.

If you create the photons, right?

I mentioned that this happens in
this, those crystals and there

you have at the same time, so this
process is completely stochastic.

So we don't have a system, but
there are fixed repetition rates.

So the creation of the
photons is something we cannot

influence when this happens.

But if it happens The two photons
will be created at the same time, and

then they are distributed to those
entities, and they will have, or if

you look on a stream of those photons,
you can find the pattern, and that's

how we do those synchronization.

We look on the Fingerprints of those
measurements if you have, let's say

you have a one second of measurement
can do some correlations and you will

find a peak where let's say most of
the signal has the same pattern, with

this, we are able to synchronize our
system to a value which is in the

region of the jitter of our detectors.

So we're talking now about 50 picoseconds,
maybe a hundred picoseconds as

synchronization rate, which is quite
interesting, especially for network guys

because they, for 5G, 6G applications,
you need sub nanosecond synchronization

which is maybe some advantage or some
quantum added value we can bring in the

future also in, into the into this game.

But the reason or the the
process we are using is really the

generation of the quantum sequence
itself for the synchronization.

So you don't need additional
hardware typically to run

those synchronization process.

But it's different to
this quantum memory stuff.

It's just locking the systems that
you can do a coincidence windows

or coincidence measurements.

So our coincidence windows or the
timeframe where we are looking

for events is just one nanosecond.

And for sure you have to synchronize
better than a nanosecond to do those

coincidence measurements, right?

So coincidence measurement for all those
who are not familiar with physics is

Alice and Bob measure at the same time.

And the time is in this one
nanosecond window an event.

This would be a coincidence.

Dan: Got it, thanks.

And I was thinking about...

Photons being received at different times.

But I think in this case, on a, certainly
on a point to point link, you rely on

the speed of light and therefore, you
can rely on the coincidence measurements.

Kevin: Yes.

Dan: Thanks.

Steve: I wanted to paint a little
bit different picture because I

think Dan, maybe I suspect tyouhave
a vision of entanglement distribution.

There's three ways to
distribute entanglement.

I think they're thinking of the one
where you have a centralized node sending

qubits both ends, but it seems like at
Quantum Jena they have Alice sending

half of the entanglement out to Bob.

And this is why it's only two clocks, if
I'm not mistaken, it sounds like that.

It seems like the entanglement is
generated at Alice and half is sent

to Bob, rather than a third node
generating entanglement to Alice and Bob.

There's also the option that Alice
and Bob both create entanglement

and send it to the center.

And

Kevin: that's where the quantum
memory in this case, so you have

Alice and Bob and maybe somebody in
the middle who received the photons.

In this case, you need a quantum memory,
to match the or to to get the correlation

between those two sent entangled
states, so that's for sure there.

You need a quantum memory or
quantum, how do you call this?

Maybe, um, a different story.

Entanglement distribution
is from one source.

Yeah.

It can be in the middle of Alice and Bob
we called our QKD also source independent

QKD, because you don't have to trust
the source, because we will measure if

it is an entanglement source, you can
see this in Bell state measurements,

if this is a truly entanglement source,
or if this is something which is, let's

say, generated from a third party.

So this you can find because you can
prove that you are in the quantum

regime and not in the classical regime.

This we will find with our measurements.

And so the source can be in the
middle but typically from a practical

perspective, we had the situation
that often the source is at.

Alice or Bob site located.

Because typically our customers, they
don't have a dedicated room in the middle.

So they typically have two data centers,
for example, and then they connect

them with the help of the entanglement.

Steve: So now, okay, so we
talked a bit about the memories.

So it seems overcoming the distance
limitations requires the quantum

memories, unless you go, I mean there's
other options, potentially go into

space, use satellites, but there's
still, there's an upper bound on how

far space communication can get you.

How do you see the future for quantum
communication for overcoming do

you believe in quantum repeater
technology, or do you think

something, something else will happen?

Maybe go right to direct transmission with
error correction, or what do you think?

Kevin: Yeah, it's a good question.

And the answer would be, I
don't know, , to be honest.

I see multiple scenarios.

If you think about, or
let's assume we, we have.

A quantum repeater technology, right?

So what would be the use case?

The use case would be really,
we go through longer distance.

Let's say we go to 200, 400,
600 kilometer distribution of

entanglement and doing QKD.

Then you can ensure that let's say A
talks to a DEF, whatever without the

knowledge of the key in between, right?

So this would be a very
interesting use case.

But actually I also see that it's
maybe easier or faster to build

up a trusted node network, right?

So where you have ABCDE knowing
the key material and but you,

they are under control of.

You or somebody you who you
trust it's maybe easier to

build up something like that.

And using this architectures for
building up networks in the future,

that's probably, we see this.

Easier to achieve than distributing
or building up a quantum memory,

quantum repeater infrastructure,
but of course there might be use

cases which it's needed then, right?

For us right now, we don't see a direct.

Business case in the next one, two,
let's say three years going over this

period, maybe it's also interesting to
have a product there, but so far as a

startup and you, if you have investors,
they are quite happy if you have some

revenue and we don't expect to have
revenues so far with quantum repeat or

quantum memory technologies, because
this is a very academic right now.

Of course there are some startups
as well in this field, and I really

appreciate that they are there.

And but for us, we decided to to
focus right now on this quantum

communication or QKD product at the end.

And also if you think about classical
telecommunication, everybody is is

talking about the limits of QKD,
but at the end, also classical.

Telecommunication is not possible to
transmit over thousands of kilometers.

You have amplifiers in between.

Yes, you have amplifiers.

That's now the case for quantum.

You cannot amplify that
because it's quantum, right?

So you have to measure and then send
it again and you will destroy the

entanglement or the measurement itself.

So that's the different now.

And but I, I think or we see at the moment
that the clients we have or the scenarios

we see will be with those trusted notes
at the beginning and then maybe use cases

come on top when you go longer distance.

But it's not unmanageable to
have trusted notes in between.

At least from our perspective,

Dan: Yeah, so thank you, Kevin.

One thing that occurred to me was around
the fact that there are no standards yet,

apart from the protocol operations and how
QKD works and key generation and so on.

Those kind of mechanisms and mathematics
have been around for decades.

When it comes to the hardware
functionality, the transparency

of the configuration, what
are your thoughts on that?

What's your stance on
making things more open?

And I guess it's in your customer's
interest to know what's going

on inside the infrastructure
that you're providing them.

So what's your stance on that?

Kevin: A , a good question.

So we really appreciate
the work standardization

organization have done so far.

So I think ETSI has done a very good
job to define interfaces for the

interconnection of let's say QKD
hardware and classical IT hardware.

So interfaces how can we bring
our quantum keys to encryptors or

whatever wants to have the quantum key.

So this is, I think, defined and
also other hardware developer have

done some protocol stuff to implement
quantum keys or external keys.

To their to their hardware.

So this is something
which is already solved.

I would say, uh, standardization
is say if you compare now QKD

concepts, that it's maybe getting
a little bit more complicated

because let's say there are so many.

Technologies around you have
DBQKD you have CBQKD you

have entanglement based QKD.

So you cannot use our system,
for example, with a CBQKD

system, so this will not work.

But We will see how this will
evolve in the in the future.

We also see some, if you look
on it or hardware right now,

you also have this issue, right?

So a system which you buy
from one provider will.

Maybe not work with another one.

We even have the case right now or last
week, where we set up a demonstration

system with SFP modules where you think
they are well defined, the interface is

clear but also there it's not the case, so
we cannot connect to SFP systems because

they are not from the same manufacturer.

Even there it's happening and We
also see this for QKD devices, so

it's maybe hard to use, let's say,
one part of Quantum Optics Jena

QKD system and things like that.

Doing the distribution
to another QKD provider.

This maybe will not happen.

But from the interface point of view
there I think we are also well aligned.

We have done a very nice demonstration
at a conference in Hannover a couple of

weeks ago with three other QKD providers.

And the key management system
was able to speak to everybody

and the setup was quite fast.

So it just was done in
six hours, I would say.

And you can use those
technologies already.

So from this perspective, the integration
into existing IT infrastructure Is doable.

So this can happen already now.

So there are many activities from
different companies, different

institutions to make this happen.

And this already works.

Another point for us is for sure.

The question of certification.

So aside of standardization, it's
how to certify such a product.

And there we see a lot
of activities right now.

Many groups and institutions are think
about how can we certify products?

How can we enable or make sure
that the security which QKD.

Will provide is really on the
implementation level the same,

like QKD in general if you want to
attack this, it's probably the the

implementation of the QKD system where
you have the where you limit the the.

Possibilities or we have to
be very carefully that you

don't do something stupid.

But this is already in an
investigation of the investigation.

Steve: It's always a challenge to come
up with standards and get people to obey

the standards and start working with
those devices to make sure that they're

working properly as they're defined.

But we mentioned in the, in your
answer, you mentioned about the future.

So I'll talk a little bit about
what's the future for Quantum Jena.

So I know, the entanglement right now
that you've described as point to point

or two party two party entanglement.

is a vision to do multi partite
entanglement to absorb some of

these other protocols that require
GHZ states across multi nodes, like

anonymous communication, for example.

What do you think about that?

Kevin: Yeah that's a really good question.

And we believe that QKD.

Has to go beyond a point to be honest.

It really comes into, we have to talk
about networks and complex networks,

not only point to point thing.

And what we have done in the past
was not the crazy stuff with, let's

say, multiplexing or yeah, using
different wavelengths in one source.

It was really the easiest.

Things first, and the easy thing
was just using beam splitters

to doing multi party QKD.

As we put a beam splitter inside one
of the photon arm, or the arm of your

entanglement, and you can have multiple
Alice, or multiple Bobs however you

want to set up something like that.

And that's also our best
selling product right now.

So it's really building up systems with
two Alice modules and one Bob, or three

Alice modules and one Bob, or one.

Alice and to Bob something like that.

What's now very interesting for certain
parties to investigate the possibilities.

And yeah, we see for us also
the future of building up this

setups where you have entanglement
distribution to create quantum keys.

And beyond that so Beyond this
simple beam splitter setup with doing

multiplexing or let's say using the
full spectrum of the of the distribution

of your photons and cutting this into
a separate pieces and then distribute

those pieces to different parties.

That's the next level for us where we have
some projects right now to develop stuff.

But this is the way I
think many parties will go.

Going to multiple parties complex networks
and really, as I said, bringing quantum

values to more than two, two entities.

This is where we have to go, I think.

And because then also the price of
the QKD system scales differently

than let's say, by a second
link you don't have to purchase.

a second QKD system and
you just have to purchase a

measurement device, for example.

That's where it's
getting very interesting.

Steve: I know we're nearing
the top of the hour.

I wanted to ask maybe a slightly more
technical question about how do you see

the challenge of overcoming using shared
fiber for both classical and quantum?

I know there's a lot of
challenges with Raman scattering.

It's not an easy problem to solve.

It's very academic at the moment,
but it seems essential that to

sell to customers, they don't
want to install additional fibers.

What do you think?

Kevin: Yes.

We also see this at the moment.

There are different voices.

So there are voices telling us we have
enough fibers, don't care about it.

Just give us a quantum or we
have a quantum channel and

then we do everything on that.

But we also see, especially for
Enterprise or B2B models they typically

have, let's say only a fiber pair and
they don't want to rent another one.

So we heavily investigating
this right now.

So multiplexing is for sure,
a very interesting topic.

It's doable, I would say, but
as you mentioned, you have so

many things taking into account.

If you go on a real network with a lot
of Different colors and a lot of light,

doing single photon measurements, right?

You see everything in such a
system and you have to to make

sure that you filter very good.

You doing some special tweaks
to, to avoid interconnections, et

cetera, but it should be doable.

The beauty of the approach we
have is we are quite flexible in

wavelengths, so we can design.

if . The whole system in a way to, to
go to different wavelengths, you can go

to the O band you can go to a dedicated
and maybe don't need the classical

or the actually data communication.

So this is now under investigation
also for us to really have a

system in the future, which
maybe fits also to those needs.

Dan: It sounds like you're looking
at more real world implementation.

You're looking at scaling systems to
support the needs of your customers.

It's really interesting stuff
that you've got going on.

So Kevin I've become aware of,
um, the governmental stance

on QKD in the US, in the UK.

I'm not sure what stance is in Germany.

But I guess it, it does.

The NCSC and NIST don't seem to be all
in on QKD, put it as simple as that.

And I I'm interested to know your
thoughts on that because obviously

that changed that really significantly
changes the market for you.

.
Kevin: We see and probably this
is not a secret if I tell this.

So the activities in Asia are quite.

Quite quite good.

You have QKD implementations
in backbone links in China, for

example, you have the Micius mission
in which is also done by China.

We have a very active community
in, in Singapore, for example.

Also some activities in South Korea.

So I would say they are leading right
now all the implementation activities.

Our point of view, especially for Europe
is there is some kind of commitment

from also governmental side, right?

So you have the European quantum
communication infrastructure activities

called short Euro QCI, where all
the member states of the European

Commission Committed to build up a
infrastructure based on QKD, which

is a huge thing in our point of view.

So it's really good to see all
the activities around in different

countries, different approaches
different testbeds different deployments.

And then let's say you have
the the statement of the NSA

and NIST in the US which.

In my perspective let's say
limits the activities of research

organizations, also startups in the U.

S.

in the past years.

There are quite some startups
around but I guess they have.

They have to fight against the opinion of
NSA and this all the time, and maybe they

are not as advanced as they could be if
they really have the support also there.

But right now we also see
some interest in the U.

S.

So a couple of months ago, we also decided
to start a dollar company in the U.

S.

as well because of that.

So we believe our product can be
a very good market fit in Europe.

And in North America as well.

So this are the main regions
we are focusing right now.

Because maybe the, we will see some
changes also in the in the in the

statement of of those entities,
because at some point they are right.

If you're talking about
QKD, the implementation of.

Of the QKD hardware is where it will
be decided also if this is a secure

system or is it, if it, if you have
some lack of of security and, uh, that's

why you have to be careful for sure.

And we are aware of this we investigate
different approaches And to make sure

that this will be a product for those
or which fits those concerns which

will be a stable product at the end.

So yes at the moment I think is
a little bit behind europe, in

quantum communication It's a totally
different story in under in other

fields, but in quantum communication
europe is quite active right now

It's the european commission.

It's also The German government
invests heavily in, in quantum

communication activities.

There are big projects around.

So one is called QNET.

The other one is called SQUAD and there
are big consortiums with many players

leading around quantum communication.

Dan: Great.

Thanks.

Believe it or not, I was actually doing
a little bit of research around around

what's, how busy academia has been,
papers, patents and citing and stuff

over the last few years for quantum
communication, quantum networking.

And you're right.

China was, a ratio of something
like four or five to one in terms

of, Um, those activities, so they're
definitely ahead in this domain.

You're right, and that's
interesting, isn't it?

How that's really occurred, and maybe
the regulation, maybe the position

of governments is a key part of that.

So I could wrap it, but I think
I did have one more question.

Yeah, so I'm jumping back a little bit.

So Steve, you mentioned multipartite QKD.

You mentioned GHZ states, which
are 3 qubit entangled states.

I know about the protocols for QKD,
BB84, there's B92 as well, I think.

I haven't gone into detail on, on,
on them too much above and beyond

what you've said on this podcast.

But when it comes to the three qubit
state , are, you and your company

working on protocols potentially that
can leverage multipartite states?

Or is there enough, are there
enough protocols on the market that

have been invented by other people
that are enough to just provide

the infrastructure to serve them?

Kevin: So right now.

We have a look on that, I would
say but as a company, you have

limited resources, I would say.

You have to balance this somehow but
we are aware of those concepts as well.

We try to be supportive or active in
research projects with new, let's say new

source designs or new source concepts,
new protocol concepts, and learning

from Actually, the academia, if this is
something for the future, or if this is

something which is purely academic, so
and if we come to the conclusion That

this might be something for the future.

We have to put resources on that as well.

It's a very interesting to see those
other concepts, But for now, we don't plan

something as a product in the near future.

So it's observing, I would say right now,

Dan: Cool.

Thank you very much.

I will wrap it this time.

So that's it.

Thank you very much for your time.

That was a fascinating conversation and
that's the usual whole bunch of questions

in my head still, but maybe for next time.

Thank you very much,

Kevin: happy to be back.

you have if you have some further
questions, feel free yeah.

Thanks for having us.

Steve: Thanks a lot for your time
and answering all those questions.

Thanks.

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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Spread the word.

It would really help us out.