**Part 3 – The future of telecommunications**

In this last part of the blog, we are analyzing the next big changes that are coming hand in hand with quantum mechanics and how they can affect telecommunications in the future.

It’s been a century since scientists discovered that, on the most intimate scales, nature operates according to principles that even today, after almost 100 years, still leaves us stunned and with our mouths open.

One of these principles is the Heisenberg uncertainty principle which states that the position and the velocity of an object cannot both be measured exactly, at the same time, not even in theory.

Thus, the more precision is achieved in determining the position of the object, the less certainty there is about its speed. And vice versa, if it is the speed of the object that is known with great precision, then there is no certainty about its position.

Einstein refused to accept quantum indeterminacy (insisting on his famous phrase “I am convinced that God does not play dice” ) and sought to show that the uncertainty principle could be violated by suggesting ingenious experiments designed to accurately determine incompatible variables such as velocity and position. The most famous of these experiments was devised by Albert Einstein at Princeton together with Boris Podolsky and Nathan Rosen in 1935 and is known as the EPR “paradox”.

Suppose, Einstein said, that an atom or subnuclear particle is disintegrated to give rise to two identical particles traveling in opposite directions from which they are allowed to travel undisturbed until a great distance separates them. By the principle of action and reaction, the speed of one fragment will be equal and opposite to that of the other:

This means that the measurement of the speed of one fragment immediately tells us that of the other, regardless of the distance at which they are.

Therefore, if we decide to measure the speed of particle A, for example, the speed of the other B will be automatically known.

This measurement on A will alter, according to the uncertainty principle, the position of A, but not presumably the position of the other particle of the pair, the one that is extremely far apart and on which there has been no interaction. Once the velocity is known, the precise position of B is now measured, thus being able to deduce both the position and the velocity of the particle B, which is a violation of the uncertainty principle.

Experimentally what was discovered is that mysteriously if we measure the speed of A exactly, we not only lose the notion of the position of A but also of B!

Likewise, if we measure the position of A exactly, we will lose track of its velocity and the velocity of B.

How can particle B know if in A we are measuring position or velocity even though the two particles may have moved millions of kilometers apart by the time the measurements are made?

According to the theory of relativity, information cannot travel faster than the speed of light, so that the instantaneous acquisition of knowledge about the particle located in a very distant place could break this fundamental principle.

In summary, this experiment shows us that particles that were once bound by an interaction, continue, in a sense, to be parts of a single system and that they will respond jointly to subsequent interactions.

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This famously counter-intuitive quantum phenomenon describing behavior that we never see in the classical world is called **Entanglement**

The direct and experimental demonstration of the paradoxical reality of the quantum world is based on modern versions of the imagined EPR experiment and was carried out in 1982 at the University of Paris-Sur by Alain Aspect.

More recently, in May 2012, an international team of scientists from Austria, Canada, Germany and Norway achieved the instantaneous transmission of information using this method between two points located 143km apart, between the observatories that the European Space Agency (ESA) they have in the Canary Islands and Tenerife (published by the journal Nature on September 6, 2012). This achievement opens a new path for quantum long-distance communications.

Scientists from the University of Bristol and the Technical University of Denmark published on Dec 2019 the results of an interesting new investigation, where they claim to have achieved “quantum teleportation” between two computer chips for the first time. Quantum teleportation works by creating pairs of entangled photons and then sending one of each pair to the sender of data and the other to a recipient.

According to those responsible for this feat, they managed to send information from one chip to another instantly, without the chips having any type of physical or electronic connection. If this achievement is confirmed, the door would be opened to the so-called “quantum internet” capable of transmitting millions of times more information than the current one.

Researchers in the US, China, and Europe are racing to create teleportation networks capable of distributing entangled photons. But getting them to scale will be a massive scientific and engineering challenge. The many hurdles include finding reliable ways of churning out lots of linked photons on demand and maintaining their entanglement over very long distances — something that quantum repeaters would make easier.

these challenges haven’t stopped researchers from dreaming of a future quantum internet yet.

On Dec 4, 2020, it was published in PRX Quantum (a Physical Review Journal) that scientists are getting closer to make a super-secure, super-fast quantum internet possible: they’ve now been able to ‘teleport’ high-fidelity quantum information over a total distance of 44 kilometers (https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.1.020317)

Another important principle for the quantum communication goal is the Quantum superposition. It is another fundamental principle of quantum mechanics that is based on De Broglie’s postulate which argued that all the particles can behave also as waves. Just as the light had a dual behavior as a wave and as a particle (the photon), electrons, and in general any material object, must have a wave behavior and consequently a dual nature as well.

An example of a physically observable manifestation of the wave nature of quantum systems is the interference peaks from an electron beam in a double-slit experiment. The pattern is very similar to the one obtained by the diffraction of classical waves.

Performing the same experiment using electrons instead of light, the pattern obtained is similar even when shooting the electrons one by one. This means that the electron is in a superposition state moving through both slits at the same time.

If we try to find out through which slit the electron passes using a device that registers the passage of the electron through the slit without impeding its journey to the screen, the pattern changes detecting the electron always going through one or the other of the holes but never through both, behaving like marble from the classical world.

** **This means that the electron is in a superposition state being at the same time in all places until it is observed and “collapses” in a real particle.

This surprising and counter-intuitive result is used in Quantum communication where particles, typically photons of light, are transmitted on a state of superposition, which means they can represent multiple combinations of 1 and 0 simultaneously. The particles are known as quantum bits or qubits.

The beauty of qubits from a cybersecurity perspective is that if a hacker tries to observe them in transit, their super-fragile quantum state “collapses” to either 1 or 0. This means a hacker can’t tamper with the qubits without leaving behind a telltale sign of the activity.

A paper by Google computer scientists appeared on a NASA website last year, claiming that an innovative new machine called a quantum computer had demonstrated “quantum supremacy.”

According to the paper, the device, in three minutes, had performed a highly technical and specialized computation that would have taken a regular computer 10,000 years to work out. The achievement could presage a revolution in how we think, compute, guard our data and interrogate the most subtle aspects of nature.

Ordinary computers store data and perform computations as a series of bits that are either 1 or 0. By contrast, a quantum computer uses qubits, which can be 1 and 0 at the same time, at least until they are measured, at which point their states become defined.

Eight bits make a byte; the active working memory of a typical smartphone might employ something like 2 gigabytes, or two times 8 billion bits. That’s a lot of information, but it pales in comparison to the information capacity of only a few dozen qubits.

Because each qubit represents two states at once, the total number of states doubles with each added qubit. One qubit is two possible numbers, two is four possible numbers, three is eight and so forth. It starts slow but gets huge fast.

“Imagine you had 100 perfect qubits,” said Dario Gil, the head of IBM’s research lab in Yorktown Heights, N.Y., in a recent interview. “You would need to devote every atom of planet Earth to store bits to describe that state of that quantum computer. By the time you had 280 perfect qubits, you would need every atom in the universe to store all the zeros and ones. “

Quantum computing is just one of the many functions towards the development of a quantum network that will deliver the quantum Internet. We can imagine entangled qubits as a pair of dice – while each can land on any number, they are both guaranteed to add to seven no matter how far apart they are. Data in one location instantly reflects data in another. By the clever arrangement of entangling three qubits, it’s possible to force the state of one particle to adopt the ‘dice roll’ of another via their mutually entangled partner. In quantum land, this is as good as turning one particle into another, teleporting its identity across a distance in a blink.

But still, quantum internet has many challenges ahead. The most significant challenges that academia and industry need to address are:

- the development of error-correcting codes for error-free quantum computing
- the building of architectures and interfaces between quantum computers and communication systems
- the development of reliable quantum memories
- the development of quantum programming languages, compilers and middle-ware stack

The future is coming fast. Be prepared!