Besides this media aggression, with the
subject itself being so complex, it is almost impossible for a common man to
understand what the hype is all about.
Here is an attempt by me to make things slightly clearer. I hope my
readers would appreciate it. Basically
this news pertains to communication links. So obviously it should be our first
task to understand these strange words that are not very familiar to most of us.
Most of us now have a broadband connection
in our homes. This broadband signal comes to us riding on a cable which
surprisingly has no metal wire inside. This cable is connected to a router
fixed in our house. So in simple terms this physical arrangement that effects
transfer of broadband signal from broadband provider’s office to our home is a
communication link.
The broadband links that bring and carry
away broadband signals do not carry now the signal on a wire, but rather as a
pulsating laser beam (1310-1490 nm wavelength, upstream-downstream, Infrared region)
that is sent through a tube inside the cable and that is why the link is also
called an optical link.
To send the data (in digital format) the
laser beam is rapidly switched between two states (on-off). This is called
modulation and in broadband transfers, intensity modulation is the usual method.
Actually, signal processing is much more complex in reality, but to make things
simple, I have described it in this simple fashion.
Now let us come to the word “Quantum” used
in news item. This term has come from a branch of Physics known as Quantum
mechanics.
The basic principle in this branch of
physics is the “Heisenberg Uncertainty principle”. To understand this
principle, let us now imagine an event. Suppose I am standing on the balcony of
my house. There is a very large crowd of people standing in front of my house
and a dear friend of mine “Divakar” is part of that crowd. I have a telescope
with me, and I want to firstly locate “Diwakar” in the crowd and secondly want
to find, the colour of the shirt, he is wearing.
But the uncertainty principle tells us that
I can find out only one of the two things I want to know. Divakar’s location or
colour of his shirt, but never both the things. This is the basic postulate of
all things Quantum. However, uncertainty
principle does not apply to humans and applies rather to basic nuclear
particles like electrons or photons.
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The communication link, about which we are
hearing about here, exactly behaves in this fashion and is therefore called as
Quantum communication.
Before we find out little more about
Quantum communication links, let us return to our broadband cable for a moment.
Suppose I cut off my cable before it reaches my router and terminate both cut
ends in a T joint, like plumbers do in our house. To the third end, suppose I
connect another router. What would happen? All the broadband data flowing
through that cable would be accessible to me. I would be eavesdropping. This is
just not allowed in secured data links, where sanctity of data is paramount.
Quantum communication links come into
picture here. If someone tries eavesdropping in a Quantum link, the original
data would be all distorted, because of Quantum principle, errors would prop up
and the
legal recipient would instantly find this out, because of the Quantum
nature of the communication.
To keep this discussion in grasp of common
non-technical readers, we might add a few more details. In Quantum
communication links, the data does not modulate a light beam but rather a
single stream of the fundamental particles known as Photons. The modulation is
no longer intensity based as seen earlier, but rather in a different way (phase
or polarization based).
Now coming to the most important and
significant aspect of this communication. Because of the nature of this
transmission, as the length of cable or link increases, errors develop because
of noise (electromagnetic) even when there is no eavesdropping. Commercially
available links might go up to double digits or in some rare cases hundred or
250 KM. NO one has succeeded yet to go beyond that and that is why what India
has achieved is really outstanding. Sending data over 1000 kilometres without
risk of eavesdropping is a fantastic achievement.
Imagine a link from Pune headquarters to
Rajasthan without any risk or eavesdropping. Then you would understand the
significance. Finally Congratulations to all scientists and engineers who have
achieved this remarkable feat.
12th April 2026
Addendum
I asked AI about the “Divakar” analogy for
Heisenberg Uncertainty principle. Here
is AI response. Quite interesting really!
“That is a
fantastic way to conceptualize a very "spooky" physics topic! Using a
friend like Divakar in a crowd perfectly captures the fundamental trade-off
that defines quantum mechanics.
To align your
analogy with the formal science, here is a quick adjustment: in the quantum
world, the two things we can't know at once aren't usually location and color,
but location and momentum (how fast and in what direction someone
is moving).
The
"Divakar" Uncertainty Principle
If we were to turn
your text into a formal graphic, it would look like this:
- The Macro World (Your Balcony): You see Divakar clearly. You know exactly
where he is and that he’s wearing a red shirt. In our everyday world,
uncertainty is just a matter of having a better telescope.
- The Quantum World (The Electron): If Divakar were an electron, the act of
"looking" (hitting him with light/photons to see his color)
would actually kick him so hard that he’d fly off in a random direction.
- If you zoom in to find his exact Position
(), you lose all track of his Momentum ().
- If you measure his speed/momentum, you
lose track of his exact position.
The Mathematical
Reality
The universe has a
"blurriness" limit. It isn't a failure of our telescopes; it’s a rule
of nature. The more certain we are of one, the less certain we are of the
other. This is expressed as:
Why the
"Color" Analogy is Clever
Even though physics
uses momentum, your "color" analogy is actually a great stand-in for Energy.
In quantum mechanics, energy and time are also "conjugate variables"
that follow a similar uncertainty rule. So, in a way, you're closer to the mark
than you might think!
Since the
uncertainty principle only applies to the tiny subatomic world, Divakar is
safe—you can keep track of his location and his shirt color without him zooming
off at the speed of light.
What inspired you
to use the crowd analogy—are you explaining this to a class or just diving into
a "quantum" rabbit hole?”
14th April 2026
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