The Qubit: introduction to quantum algorithms


Sometimes, in popular settings, the quantum computer is labeled as a particular “incredibly faster” computer. Although this consideration is not entirely far from reality, it is necessary to make some clarifications.

The quantum computer is structurally distinct from a classical computer, so much so that the logic that determines its internal processes differs from the common one, as it can only be described thanks to the laws of quantum mechanics.

In order to highlight the aspects of innovation brought about by the quantum computation model, it is necessary to proceed with a reference to the classical computation model or to the information processing method by today’s computers.

The data is coded through bit sequences. A single bit represents the classical unit of information and is described by two possible states 0 and 1, therefore any data processed by a computer is represented as a binary string (succession of 0 and 1).

The most distinguishing element is identified precisely in the different unit of information adopted by a quantum processor, the classical concept of bit is overcome and generalized by that of quantum bit or qubit.

The quantum states that describe the qubit are not limited only to the values ​​of 0 and 1, as happens for the bit, but can assume infinite intermediate configurations, realizing the phenomenon that in quantum mechanics is called superposition.

By exploiting this phenomenon, the scientific community has devised some algorithms through which the quantum computer is able to calculate a certain result in a much smaller number of steps than its classical counterparts.


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The authors

Veronica Cristiano, a bachelor’s degree in Mathematics from the University of Pisa and a master’s degree in Mathematics with a specialization in Cryptography at the University of Trento, joined the Telsy Cryptography research group in mid-2021.

Francesco Stocco, a master’s degree in Mathematics at the University of Padua and the Université de Bordeaux attending the course of study “Algebra Geometry And Number Theory” (ALGANT), joined the Telsy research group in Cryptography at end of 2020 focusing in particular on issues related to quantum technologies.