> https://phys.org/news/2021-06-quantum-cascade-lasers-private-free-space.html

Quantum Key Distribution QKD and the ridiculous cost
and waiting time for this paper tech is totally unnecessary
for building your own guerilla meshnets p2p among
your neighbors reaching around the globe right now TODAY.

Just one year of payments to your shitty cable/dsl ISP you
can build a simple box with two NICs to each of two neighbors
for a redundant mesh path... copper, fiber, RF, laser, etc.
Literally under $750 one time HW will last you not one year
but 10 years, under $10/month.
Peer every 100 nodes with outside internet for $0.20/Mbit/month
until your meshes can span 1000's of km to be your
own complete p2p tier-1 meshnets. You already have
strong opensource crypto to independently encrypt every
p2p link using PSK, rotation, quantum-safe algos, etc.

BTW, all ISPs up through Tier-1's refuse to independently
encrypt and pad each physical link because they love spies
and spying. They won't encrypt the physical links, your meshnet will.

It costs so little to build it yourself eliminating middleman ISP
that there's great small business profit to be made selling the
boxes and copper, fiber, laser, RF gear to those who want
to link up to the mesh but can't follow the self-HOWTO.

And it's a great meetup to spread cryptoanarchy,
cryptocurrency, etc.

> WiFi routers

Consumer WiFi schemes suck at reliably moving
bandwidth 24x7 and are a channel allocation and
interference nightmare and should not, certainly not
without directed antennas, be used for building a real
p2p one-owner-per-node meshnet unless you have
no other means to reach a peer node directly over
copper, fiber, laser, guerilla UWB RF, etc.
And if you still can't reach, then encrypt and tunnel it
over cable/dsl ISP until you can.

> WiFi routers should have incorporated
> ability to communicate between nearby units.  The vast majority of WiFi
> routers are within hearing distance of other routers.

Some WiFi can do raw mode or at least ad-hoc,
but the problem is it's all omnidirectional over the
same limited spectrum... too many speakers, too
much density, too much power to override others, all
broadcast, plus all the owners who give zero shits
about coordinating a plan with anyone else because
they're not in it to do a common goal of p2p meshnet,
they just want to blast their phones and laptops to
their ISP screw their neighbor, and good luck trying
to talk to them about channel allocation/power you see
via your analyzer... so without a common meshnet project
such WiFi ends up being a race to spam itself to death.

With a guerilla p2p meshnet around the world,
you're specifically engineering to build the most
reliable interference-free distributed-ownership
encrypted fastest direct p2p-node links you can.



"
Free-space optical communication, the
communication between two devices at a distance
using light to carry information, is a highly
promising system for achieving high-speed
communication. This system of communication is
known to be immune to electromagnetic
interference (EMI), a disturbance generated by
external sources that affects electrical circuits and
can disrupt radio signals.
While some studies have highlighted the possible
advantages of free-space optical communication,
this system of communication has so far come with
certain limitations. Most notably, it is known to offer
limited security against eavesdroppers.
Researchers ... have recently introduced a
unique system for more secure free-space optical
communication based on a technology known as
quantum cascade laser, a specific type of
semiconductor laser that typically emits mid-infrared
light.
"The core idea behind our research is that private
free-space communication with quantum key
distribution (i.e., based on quantum physics
properties) is promising, but it is probably years
away, or even further," ... "Currently, the main limitations
of this technology are the requirements for cryogenic
systems, very slow data rates and costly
equipment." Colleagues propose an alternative to
previously proposed systems for achieving private
free-space communication, which implement a
cryptographic protocol based on the laws of
quantum mechanics. The new system they devised
is based on the use of two uni-directionally coupled
quantum cascade lasers.
The researchers' approach combines what is
known as chaos synchronization with the mid-
infrared wavelength of quantum cascade laser
technology. Chaos synchronization is a specific
property that has been examined in the context of
semiconductor lasers for decades.
"Chaos synchronization is the key to private
communication, while mid-infrared wavelength
means that the attenuation of the atmosphere is
low in comparison with near-infrared wavelength,
where most of the semiconductor lasers emit,"
Spitz explained. "We can thus envision
transmission with a very long range and with
immunity to the atmospheric conditions. Moreover,
the mid-infrared wavelength implies stealth, as the
background radiation is in the same wavelength
domain."
The mid-infrared wavelength of the quantum
cascade lasers makes it even harder for a potential
eavesdropper to decipher information exchanged
using the researchers' system. This means that the
security of communications is increased further.
"I feel the most notable achievement is the
successful chaos synchronization between two
QCLs," Spitz said. "For a long time, the possibility
to generate temporal chaos in this type of structure
was controversial because they rely on a different
technology, in comparison with most of the
semiconductor lasers, which overall makes QCLs
more stable, so not really prone to chaos. A few
years ago, we experimentally demonstrated that
QCLs can generate temporal chaos, and we now
took this one step further by achieving private
communication based on chaos synchronization."
So far, the researchers merely described a proof o
concept of their proposed system, where the
distance between the two quantum cascade lasers
is merely of one meter. This is not a realistic
configuration for free-space communication.
However, they hope to improve their system, to
make it more suitable for real-world
implementations.
"We plan to increase this distance to hundreds of
meters, then kilometers, in order to build an
operational system," Spitz said. "Apart from
quantum cascade lasers, there are other mid-
infrared semiconductor lasers, such as interband
cascade lasers (ICLs). We plan to repeat the same
experiment with ICLs, to determine the best
configuration for private communication at mid-
infrared wavelength."
More information: Private communications with
quantum cascade laser photonic chaos. Nature
Communications(2021).
DOI: 10.1038/s41467-021-23527-9.
"