# How does quantum computing work?

**In the next few years we will move from the digital age to the quantum age. In this article we present the basic elements of quantum computing, one of the technologies with the most disruptive potential.**

Digital transformation is driving change in the world faster than ever. Would you believe that the digital age is about to end? **Digital literacy** has already been identified as an area where open knowledge and accessible opportunities to learn about technology are urgent to address gaps in social and economic development. Learning from the key concepts of the digital age will become even more critical in the face of the imminent arrival of another new technological wave capable of transforming existing models with amazing speed and power: **quantum technologies** .

In this article, we compare the basic concepts of traditional computing and quantum computing; and we also began to explore its application in other related areas.

## What are quantum technologies?

Throughout history, human beings have developed technology as they have understood how nature works through science. Between the years 1900 and 1930, the study of some physical phenomena that were not yet well understood gave rise to a new physical theory, **Quantum Mechanics** . This theory describes and explains the functioning of the microscopic world, the natural habitat of molecules, atoms or electrons. Thanks to it, it has not only been possible to explain these phenomena, but it has also been possible to understand that subatomic reality works in a completely counterintuitive, almost magical way, and that events take place in the microscopic world that do not occur in the macroscopic world.

These **quantum properties** include quantum superposition, quantum entanglement, and quantum teleportation.

- The
**quantum superposition**describes how a particle can be in different states at once. - The
**quantum entanglement**describes how two particles as separate as desired may be correlated so that, to interact with the one, the other learns. - The
**quantum teleportation**using quantum entanglement to send information from one place to another in space without having to travel through it.

Quantum technologies are based on these quantum properties of the subatomic nature.

In this case, today the understanding of the microscopic world through Quantum Mechanics allows us to invent and design technologies capable of improving people’s lives. There are many and very different technologies that use quantum phenomena and some of them, such as lasers or magnetic resonance imaging (MRI), have been with us for more than half a century. However, we are currently witnessing a technological revolution in areas such as quantum computing, quantum information, quantum simulation, quantum optics, quantum metrology, quantum clocks or quantum sensors.

## What is quantum computing? First, you have to understand classical computing

To understand how quantum computers work, it is convenient to first explain how the computers that we use daily work, which we will refer to in this document as digital or classical computers. These, like the rest of the electronic devices like tablets or mobile phones, use bits as fundamental units of memory. This means that programs and applications are encoded in bits, that is, in the binary language of zeros and ones. Every time we interact with any of these devices, for example by pressing a key on the keyboard, strings of zeros and ones are created, destroyed and / or modified within the computer.

The interesting question is, what are these zeros and ones physically inside the computer? The states zero and one of the bits correspond to electrical current that circulates, or not, through microscopic pieces called transistors, which act as switches. When no current flows, the transistor is “off” and corresponds to a bit 0, and when current is “on” and corresponds to a bit 1.

In a more simplified way, it is as if bits 0 and 1 correspond to holes, so that an empty hole is a bit 0 and a hole occupied by an electron is a bit 1. It is for this reason that these devices are called electronic . As an example, figure 1 shows the writing in binary language of some characters. Now that we have an idea of how today’s computers work, let’s try to understand how quantum computers work.

## From bits to *qubits*

The fundamental unit of information in quantum computing is the *quantum* bit or *qubit* . The *qubits* are, by definition, quantum systems two -now levels see examples- that the same as the bits may be at the low level, which corresponds to a state of low excitation or energy defined as 0, or in the high level , which corresponds to a state of greater excitation or defined as 1. However, and here lies the fundamental difference with classical computation, the *qubits*They can also be in any of the infinite intermediate states between 0 and 1, such as a state that is half 0 and half 1, or three-quarters of 0 and one-quarter of 1. This phenomenon is known as quantum superposition and is natural in quantum systems.

## Quantum algorithms, exponentially more powerful and efficient computing

The purpose of quantum computers is to take advantage of these quantum properties of *qubits,* as quantum systems that they are, to be able to run quantum algorithms that use superposition and entanglement to offer much greater processing power than the classical ones. It is important to point out that the true paradigm shift does not consist in doing the same thing that digital or classic computers do – the current ones – but faster, as can be erroneously read in many articles, but rather that quantum algorithms allow certain operations in a totally different way that in many cases turns out to be more efficient – that is, in much less time or using much less computational resources.

Let’s look at a concrete example of what this implies. Let’s imagine that we are in Bogotá and we want to know which is the best route to get to Lima out of a million options to get there (N = 1,000,000). In order to be able to use computers to find the optimal path, we need to digitize 1,000,000 options, which means translating them into bit language for the classic computer and *qubits.*for the quantum computer. While a classical computer would need to go one by one analyzing all the paths until the desired one is found, a quantum computer takes advantage of the process known as quantum parallelism that allows it to consider all the paths at once. This implies that, although the classical computer requires the order of N / 2 steps or iterations, that is, 500,000 attempts, the quantum computer will find the optimal path after only √N operations on the register, that is, 1,000 attempts.

In the previous case the advantage is quadratic, but in other cases it is even exponential, which means that with n *qubits* we can obtain a computational capacity equivalent to 2 ^{n} bits. To exemplify this, it is common to say that with about 270 qubits one could have more base states in a quantum computer – more different and simultaneous strings of characters – than the number of atoms in the universe, which is estimated to be around 2 ^{80} . Another example is that it is estimated that with a quantum computer of between 2000 and 2500 *qubits* , practically all the cryptography used today (known as public key cryptography) could be broken.

## Why is it important to know about quantum technology?

We are in a time of digital transformation in which different emerging technologies such as blockchain, artificial intelligence, drones, Internet of things, virtual reality, 5G, 3D printers, robots or autonomous vehicles have an increasing presence in multiple fields and sectors. These technologies, called to improve the quality of life of human beings by accelerating development and generating social impact, are advancing today in parallel. Only rarely do we see companies developing products that exploit combinations of two or more of these technologies, such as blockchain and IoT or drones and artificial intelligence. Although they are destined to converge thus generating an exponentially greater impact,

Quantum technologies, due to their disruptive potential, are expected not only to converge with all these new technologies, but also to have a transversal influence on practically all of them. Quantum computing will threaten the authentication, exchange and secure storage of data, having a greater impact on those technologies in which cryptography has a more relevant role, such as cybersecurity or blockchain, and a less negative impact but also to be considered in technologies such as 5G , IoT or drones.

Soon in Open to the Public we will highlight some specific examples of how the application of quantum technologies is being disruptive in various sectors and how open knowledge helps us prepare for these disruptions. Meanwhile, we invite you to learn in depth about the subject through the publication

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