Fri. Apr 19th, 2019

Quantum physics will change our lives

La física cuántica cambiará nuestras vidas

Internet invade our environment. Computers, phones, watches. In the coming decades, the interconnection It will also reach our homes. To the vehicles. To the clothes, even. There will be cars that drive alone. Intelligent refrigerators that make the purchase for us. Sensors in shirts that monitor our health at all times. Our home will know when to turn on and off the heating to keep us comfortable or when to call the doctor if we are sick.

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But all connections involve risks. The information it is a valuable treasure and there are those who specialize in stealing it,
. The companies that manage data invest a lot of efforts and resources in shielding them, in a constant race against these pirates of the 21st century.

"Today there are very secure systems that make it difficult to spy on communications, but not impossible," says Lluís Torner, director of the Institute of Photonic Sciences (ICFO) in Castelldefels. No digital data is 100% secure, no personal messages, no medical records, no defense information or commercial transactions. And as the connections expand, so does the risk.

"If the information is not secure, it is a disaster. We will not be able to use all the technology that comes, "explains Carlos Abellán, co-founder and executive director of the Quside company.

But, what if someone invented a way to transmit information in a completely secure way, proof of any hacker? That is precisely the promise of quantum communications, a technology in development that can guarantee confidentiality not by the shielding of protocols and algorithms, but by the very laws of physics.

The security of connections is vital to be able to use the technology that comes

This type of communications is developing in the so-called second quantum revolution. After the laws of quantum mechanics were used in the first to develop new technologies, now we aspire to directly use the quantum elements, such as atoms or photons, to go further, since their behavior is radically different from that of the matter on a larger scale.

In the quantum world, for example, a particle can be in two states simultaneously while nobody observes it, but, if someone tries to detect it, it will opt for one of the two. It is what is known as quantum superposition. It would be like throwing a coin in the air with your eyes closed. As long as we do not see what result has come out, it can be both face and cross, with a 50% chance for each option: the coin would have two overlapping states. As soon as we look, we will know if we have drawn heads or tails, so the probability will change.

Another strange property is the quantum entanglement. Two particles can be linked so that they share the same state despite being separated kilometers away. "It would be as if I were in Castelldefels and you were here in Barcelona, ​​that both of us would throw a different coin into the air and we would always have the same result. If I make a face, you too. And if I get cross, to you equal ", illustrates Hugues de Riedmatten, researcher Icrea in the ICFO.

"The truth is that we do not know why the Universe behaves like this. But we can take advantage of it, "says Carlos Abellán. According to experts, in the medium term communication will be the field that benefits the most from quantum technologies.

The current cybersecurity is based on encrypting the data through two factors. First, you have to create a lock that protects the information, in the form of an algorithm. The problem is that all algorithms are built following logical sequences and, therefore, through logic you can develop keys that open those locks with relative ease. To avoid this, locks are created that can be opened only with randomly created keys, that is, keys of numbers generated at random, with which logic is no longer enough to force them.

But there is a second problem: the recipients of the encrypted messages have to be able to decipher them. Therefore, you must also send the keys that allow you to decrypt them. And, if someone intercepts this key without a trace, the security vanishes.

Receiver and sender will know instantly if someone tries to intercept the message

That's where quantum technologies come in. The objective is to create a communication channel based on quantum bits to distribute the keys. That is, particles such as atoms or photons that have two superposed states, which share at a distance with other particles, explains Valerio Pruneri, an Icrea researcher at ICFO. Thanks to the entanglement and the superposition of the quantum bits, it is possible to send keys so that, if someone tries to get them, both the receiver and the sender of the message realize that they are being watched. "If someone tries to eavesdrop, it changes the state of the quantum bits and the two parties know it," says Pruneri. Thus, upon discovering that the key has been stolen, they can interrupt the communication and generate a new lock.

Pruneri leads the CiViQ project, with the goal of developing this technology so that it can be applied on a large scale. It is part of the European program Quantum Flagship, which was presented to the public of the Mobile World Congress, held in Barcelona between February 25 and 28, and which together with the Human Brain Project and the Graphene Flagship is one of the research projects most ambitious in Europe, with an investment of one billion euros.

The idea is not to quantumly transmit all the encrypted information, but only the keys to decrypt it. "The main challenge is to take quantum technology out of the laboratory, apply it to the real world and verify that it can be integrated with classic networks at an affordable cost," says Valerio Pruneri. "The communications networks are very aggressive with the quantum elements," explains Vicente Martín, professor at the Polytechnic University of Madrid (UPM) and director of the Computational Simulation Center (CCS), who also participates in CiViQ in close collaboration with Telefónica. "A classic fiber optic signal has about 100 million photons," while a quantum signal is encoded by a single photon. "It is very difficult to reconcile the classic communications with the quantum ones", underlines Martín. The CiViQ project has almost 10 million euros to pursue that goal.

In Spain, CiViQ also participates in two start-ups, VLC Photonics, which emerged from the Universitat Politècnica de València (UPV), and Quside, which was born from an ICFO project. Quside has created the first integrated chip to generate encryption keys based on quantum principles. "The current random numbers used in encryption are not really random, since they are born of algorithms," says Carlos Abellán. That is another weak point, because a sufficiently powerful machine, or a quantum computer, could get to decipher them. "Quantum is the only way to generate real randomness." According to Abellán, the Quside chip will begin to be applied in the next few years in data centers, autonomous cars and other devices connected to the internet of things.

"We are already able to establish secure communications from one point to another separated by a distance of about 400 kilometers," says Pruneri. "In the long term, the goal is that any point in the world can be connected securely with any other point, using satellites combined with fiber optic cables and quantum repeaters, which are being developed and will allow the interlacing to be distributed over longer distances" .

The Schrödinger internet

Superimposed and interlaced.
Quantum physics has opened new doors in computing: superposition and entanglement can be applied to create computers capable of solving problems that are beyond the reach of conventional computing. It is about storing bits not in the classic plates and hard disks, but in quantum particles. Instead of having two exclusive states like the conventional bits (0 and 1), the quantum bits, or cubits, can be in two overlapping states: 0 and 1 at the same time, which multiplies the possibilities.

The main limitation.
Quantum computers have a weak point. "The number of quantum bits is very limited because they are very difficult to control," says Hugues de Riedmatten of ICFO. The current record in quantum computing is at 50 cubits and "for the moment there is no quantum computer that has done a better job than a classic one".

Computer networks.

But there is a way to overcome this limitation: the quantum internet. Physicists have set out to develop a network of quantum computers connected through the entanglement of their cubits. Thus, when adding the capacities of the different machines, the total power of the system will increase exponentially, according to Riedmatten, which participates in the QIA project of the Quantum Flagship to pursue that goal. Quantum internet can also help increase the distances of quantum communications and improve their security.

New possibilities
But "the most important thing is that with quantum computing you can do things that a classic computer can not do," says de Riedmatten. Quantum computers would allow us to study the behavior of matter on a scale that is impossible today. For example, a quantum simulator could be used to study how proteins fold in different ways, a key process in diseases such as Alzheimer's or Parkinson's. Or help develop new drugs or materials with unusual physical properties that are not fully understood today, such as some types of superconductors. According to de Riedmatten, it is difficult to predict when quantum computing will become a reality, but "it will be a paradigm shift".

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