You’ve just captured the intel and now you
have to get it back to the CIA, ASAP.
You have the latest encryption, but there’s
still a chance the network could be compromised,
and there’s no way to know.
Do you risk it?
This scenario could be from a spy thriller
or a video game, but it’s not totally absurd.
In fact, scientists across the globe are working
on a solution to this very problem.
And this week, physicists at Princeton and
the Australian National University have made
some progress.
In a paper published in the journal Nature
Physics, they announced that they’re a little
closer to making a long-range quantum internet
a reality.
A quantum what?
Alright, we’re going to need to take a step
back here.
A quantum internet, which would encode information
using tiny particles, could be the perfect
way to send messages that are completely secure.
You’ve probably heard about quantum computing,
which uses quantum bits, or qubits, instead
of the ones and zeroes our regular computers
use.
Qubits are special because they’re based
on the physical properties of particles, like
an electron’s spin.
An electron’s spin can be up or down, but
because this is quantum mechanics, where everything
is complicated and weird to think about, its
spin can also be up and down at the same time.
That’s what’s known as superposition,
where particles like electrons or photons
are in two opposite states at once.
It makes no sense in the context of how we
normally experience the world, but that’s
just the tip of the very, very strange quantum
mechanical iceberg.
On the scale of tiny particles, the classic
principles of science start to break down,
and things happen that seem like they should
be impossible.
But based on a lot of experiments and math,
we know they are happening.
So even though it can be hard to wrap our
brains around it, we’ve just had to accept
that particles can do things like be in two
opposite states at once.
With quantum computing, we’re using this
weirdness to our advantage in two main ways.
First, you can encode more information in
a qubit than in a conventional bit.
Two conventional bits, for instance, will
have one of four possible values: 00, 01,
10, or 11.
Each qubit, though, can be both a zero and
a one at the same time, so two qubits can
be all four possibilities at once.
As you add more qubits, the amount of information
you can store and process goes up incredibly fast.
With a 300 qubit computer, you could do more
calculations at once than there are atoms
in the universe.
Basically, a big enough quantum computer would
be infinitely more powerful than the best
supercomputer we could ever build the regular
way, and it’s why physicists have been geeking
out over this ever since they realized it
was theoretically possible.
The second main advantage of quantum computing
is that you can use qubits to send information
in a way that’s inherently secure.
When you encrypt information, you jumble it
up so that when you send it, anyone listening
in won’t be able to decipher the message.
But the person you’re sending it to, who
you actually /want/ to read it, needs to be
able to decode it, so you send them a key
they can use to decrypt the message.
Problem is, if someone’s eavesdropping on
the key, they’ll be able to decode it too.
There are lots of ways cryptographers try
to get around this, but they all have some
flaws, and in theory could be hacked eventually.
Quantum computing, on the other hand, might
be the perfect answer because of another weird
rule of quantum mechanics:
When you measure something like an electron’s
spin, the act of taking the measurement actually
/changes/ some of the electron’s properties.
So if you use qubits to send your friend Bob
a key, and your archnemesis Eve intercepts
any of the particles before sending them along
to Bob, you and Bob will be able to tell that
someone messed with the qubits before he got
them.
In other words: no one can eavesdrop on your
key without you knowing about it.
This is next-order encryption, and we’d
like to take advantage of it.
But that means having more than one quantum
computer, and hooking them up over long distances.
Basically, we want to build a quantum internet.
And that’s where this new research comes
in.
We already have a massive global network of
fiber optic cables, so it’d be great to
piggyback on our existing infrastructure as
we build the internet of the future.
And fiber optic cables are a pretty good choice,
because you can use photons of light as qubits.
But there are two big challenges.
First, to use those fiber optic cables, you
need to transmit photons with a certain wavelength.
Second, qubits are super fragile.
If anything interferes with the particles
before you transfer your message, you’ve
lost your data.
So you need to keep your qubits stable.
We’ve already discovered how to use certain
materials to store quantum information for
long enough to send it through a network,
but they don’t work on the right wavelength
for our fiber optic cables.
And the materials that are compatible with
those cables can store information for only
a fraction of a second.
That’s too short.
To solve this problem, the Australian team
wanted to find a way to lengthen that time.
So they started experimenting with a crystal
that had some erbium in it.
Erbium is a rare earth metal, and a crystal
with erbium ions in it can work on a wavelength
that matches fiber optic cables, but it can
only store quantum information for short bursts.
To increase that timeframe, the group applied
a super-strong 7 Tesla magnet.
That’s the strength of the most powerful
MRI machines.
Magnets are helpful because they can freeze
electrons in the crystal in place, which keeps
them from interfering with and destroying
the data.
And … it worked!
The magnet increased the crystal’s storage
time to 1.3 seconds.
Now, that might not seem very long, but it’s
a 10,000-fold improvement over what scientists
could do before — and it’s good enough
for a quantum internet.
Other experts have estimated that with quantum
repeaters to boost the signals, you need storage
times of just 1 second to send messages 1000
kilometers.
So, where’s our quantum internet?
Any kind of widespread network is still a
ways off.
For one thing, the Australian setup required
very low temperatures to work: 1.4 Kelvin,
or -272 Celsius.
That’s seriously cold, and seriously expensive
to maintain.
And, of course, there’s that strong magnetic
field.
The researchers think their material will
still work with a less powerful 3 Tesla magnet,
but it’s not like that’s nothing.
Think of a more typical MRI machine instead
of the most advanced.
Not exactly chump change.
Even if we solve those problems, quantum networks
might never be used for things like watching
this video, or to execute run-of-the-mill
Google searches.
You know, like ‘quantum repeater’ or ‘erbium
crystal’.
They’ll be reserved for super-secret situations
when you want your communication to be absolutely secure.
So, maybe your banking, but probably more
like high-level international intelligence.
Basically, spy stuff.
But no matter who ends up using it, the quantum
internet will be a major upgrade for the world
of cryptography.
Thanks for watching this episode of SciShow
News, and if you want to learn more about
quantum computers, you can check out an earlier
episode we did about another amazing quantum
computing breakthrough.
