Quantum computing: a leap as big as the one between the abacus and modern computing
If the 19th century was the age of the machine and the 20th century that of information, the 21st century will be the quantum age. It is not hyperbole. William Daniel Phillips, Nobel laureate in Physics in 1997, believes that quantum computing represents a technological leap without comparison to those we have experienced so far, greater even than that between the abacus and current computing.
Quantum mechanics emerged at the beginning of the last century as the field of physics that describes the behavior of nature at subatomic levels (for example, of particles such as photons or electrons), for which classical mechanics could not find a satisfactory solution. Later, in the early eighties, the American physicist Richard Feynman proposed the construction of a computer whose internal states were quantum variables. This Nobel laureate, along with fellow American Paul Benioff and Russian mathematician Yuri Manin, laid the foundations for this new computation, thus starting the second quantum revolution. This attracted the interest of the security agencies of several governments, when the American physicist Charles Bennett and the Canadian Gilles Brassard proposed the first quantum cryptography protocol and the American mathematician Peter Shor an algorithm that drastically reduces the execution time of the factorization of numbers, one of the foundations of current cryptography.
Like classical computing, it is based on the concept of bit (which can take the value 0 or 1), in quantum computing the cúbit (of English qubit, quantum bit), is the minimum unit of information. Unlike the bit, which can only be in one of these two states, the cúbit It can be found simultaneously in states 0 and 1. It is as if we were going from a light switch that turns it off or on, to one that lets us have many intermediate states. So with 10 cubits we would have 1,024 simultaneous states and, each time we add a cúbit, we double the computing power.
It must be taken into account that generating and managing cubits is a huge scientific and engineering challenge, as you have to avoid cubits interact with the environment until they are measured, for which, in some cases, the circuits are cooled to temperatures lower than that of deep space (close to absolute zero, -273 degrees Celsius). Despite this, today quantum computers still have many errors, since the coherence of the values of the qubits is lost.
There are two ways to work with quantum computers. One is based on the so-called quantum temple (quantum annealing) ―Used by the D-Wave company― in which the problem to be solved corresponds to a model whose solution is the lowest energy state of the system and which are suitable for executing optimization problems. The other is that of computers that support gate-based quantum computing ―used by IBM, Google or Rigetti―, in which a problem is decomposed into a sequence of primitive basic operations, which are performed by quantum gates. It must be taken into account that quantum computers do not replace current ones, but rather coexist in hybrid architectures in which a classical computer sends the appropriate instructions to the quantum computer, collecting and processing the results that it returns.
Quantum computers not only allow us to simulate nature much better, but also to execute algorithms that for “classical” computers are impractical, since they would take too long – in some cases, even the largest supercomputer in the world, several million years – or would need an almost infinite memory. In fact, in 2019 Google announced “quantum supremacy” with an experiment designed by the Spanish Sergio Boixo: a quantum computer managed to do in a few minutes something that would take a conventional supercomputer thousands of years.
There are hundreds of interesting applications for this new type of computing in fields such as economics and financial services, chemistry, medicine and health, logistics and supply chain, energy and agriculture. And, of course, quantum computing has a fundamental impact on cybersecurity and Artificial Intelligence. This has prompted many governments (the United States, the European Union, the Netherlands, France or Germany) to include quantum technologies in their research agendas and ecosystems.
In order to contribute to making quantum computing a reality, a group of researchers and computing professionals [entre los que se incluye el firmante de este artículo] proposed in the Manifesto on Software Engineering and Programming Quantum, the involvement of everyone: companies and professionals, identifying the projects that can benefit from this technology; the scientists, trying to solve the outstanding questions; governments supporting research and transfer, and academics, considering quantum computing in curricula and study plans. Quantum computing offers the opportunity to experience the same as the pioneers of computing in the sixties of the last century and be protagonists of this new era.
Mario Piattini Velthuis. Professor of Computer Languages and Systems at the University of Castilla-La Mancha
Chronicles of the Intangible is a space for the dissemination of computer science, coordinated by the academic society SISTEDES (Society for Software Engineering and Software Development Technologies). The intangible is the non-material part of computer systems (that is, software), and its history and its evolution are related here. The authors are professors at Spanish universities, coordinated by Ricardo Peña Marí (professor at the Complutense University of Madrid) and Macario Polo Usaola (professor at the University of Castilla-La Mancha).
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