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World Quantum Day 2022: IIT-CNR and the Quantum Internet research studies

Celebrating World Quantum Day, the international day to promote the public understanding of Quantum Science and Technology.

Today is World Quantum Day, the international day to promote the public understanding of Quantum Science and Technology: a frontier research that not only will determine an evolution of computers, but will probably mark the beginning of a new era for the Internet.
IIT-CNR is naturally involved in this new field of studies, participating in two important research projects, HPCQS and Quancom, and being part since February 2022 of the IBM Quantum Network.


Claudio Cicconetti, IIT-CNR researcher who is currently studying Quantum Internet, has told us something about his most recent researches, dedicated in particular to the quantum routing problem.
To learn more about Quantum Internet you can also watch Cicconetti’s speech
“Beam me up, Scotty”, or teleportation and other (useless) lies on quantum networks.


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The next few years will see the development of the Quantum Internet, which will interconnect quantum computers in much like the way the Internet has been doing for “classical” computers (and smartphones, video game consoles, smart things, etc.) for the past 50 years. A couple of questions come to one’s mind. Why do we need a Quantum Internet? If we do, why don’t we have it already?

To answer the first question, let us consider that a quantum computer is fundamentally different from the computers we use every day. It uses quantum bits (qubits), which can each represent any possible combination of two states (for example a qubit can encode “90% the light is ON and 10% the light is OFF” or “45% ON and 55% OFF” and so on), whereas by contrast the classical bits are limited to a single value (the light can be ON or OFF, but never a mix of the two). Also, these qubits can be entangled to produce a new quantum state in which the contribution of each qubit becomes inextricably linked to that of the others, even if we displace one of them to another far away location.

Thanks to these properties, quantum computers in the future will fulfill the growing needs of science, industry, and society. But, we have learnt in the past decades that the interconnection of computing infrastructures can accelerate further the evolution of information technologies and create new unforeseen applications: think of the cloud and what it means to us today! The same can happen with quantum computing, but unfortunately the existing communication infrastructure (a.k.a. the Internet) cannot be used “as is”, since it was designed to transfer bits, not qubits.

This takes us to the second question: if having a Quantum Internet is useful, then someone is already building that, right? Well, no. Not yet. The problem is the following. Remember the entanglement of qubits? It turns out that enabling entanglement between any two quantum computers in the world is possible theoretically, but very difficult practically. In particular, we would need a so-called quantum repeater, which is a (as-yet-theoretical) device that can teleport a qubit from one node to the next one until the final destination is reached. Quantum teleportation is the operation needed to transfer the state of a qubit from one system to another, and it is the best we can do since it is just not possible to copy a qubit, like routers and switches do at a rate of trillions per second with classical bits, because of a fundamental law of physics known as the “no-cloning theorem”. However, quantum communication technologies are evolving very fast, and in the research community it is widely agreed that the mythical quantum repeater will become reality soon, thereby unlocking immense possibilities offered by the materialisation of the Quantum Internet.

In the meantime, at IIT within the Ubiquitous Internet research group, we are studying solutions for the Quantum Internet, so that we will be ready when it comes to us. One of our ongoing activities is about the quantum routing problem. In the Internet, routing is the process that decides which is the best path to reach one computer from another (for example, how to reach Google’s servers to issue a web search query from one’s mobile phone). This process is performed very efficiently based on algorithms and protocols that have been designed under the assumptions of transferring packets of classical bits, which for this reason are ineffective to select the best path to establish remote entanglement in the Quantum Internet.
In the last decade, some of our fellow researchers have investigated this problem and found elegant solutions for quantum applications that require a constant rate of entanglements; one such example is Quantum Key Distribution (QKD), which can be used to transfer messages of classical bits with unconditional security, that is in a way that makes it impossible for a third party to eavesdrop the content. On the other hand, we are focusing on a different kind of application, which has been neglected so far in the community but is emerging as a promising opportunity: distributed quantum computing, which allows multiple quantum computers to pool their resources together and solve problems that are unattainable by any of them alone. We believe this application will be especially important in the first phases of development of the Quantum Internet, when the quantum computers interconnected will have relatively modest capabilities, precisely as happened at the dawn of the Internet. However, distributed quantum computing uses a variable rate of entanglement, which makes it different from all other applications addressed so far, and hence calls for a different approach to routing, which we are studying by means of analysis and simulation tools.

The interested reader can find further details and initial results on quantum routing for distributed quantum computing here.

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