# Basics

QuBit, quantum teleportation and entanglement. These terms are essential for understanding quantum technologies such as the quantum computer or quantum networks. Using graphs and small examples, these three terms are discussed in more detail in this article. In the text, as a supplement, there are *Excursus* that contain more detailed information on the content such as mathematical definitions and derivations.

## Excursus: Why quantum computing? The Grover Algorithm

This example uses the Grover algorithm to illustrate why quantum computers are superior to classical computers in terms of computing time.To find an element from an unsorted database with N elements, a computing time is required that is proportional to O(N) (large O notation). Already in 1996 Grover could show that with an algorithm based on quantum technology the number of computational steps can be reduced to an order of O(N^{0,5}).

By reducing the number of computational steps, Grover’s algorithm reduces the time required to find an item in a database. This algorithm is one of several that exploit the properties of quantum phenomena to achieve an increase in computational speed [3].

*further information about the Grover algorithm:* https://qiskit.org/textbook/ch-algorithms/grover.html