## What is a quantum computer?

A quantum computer is a processor that functions according to the laws of quantum mechanics. Unlike a conventional computer, a quantum computer does not work on the basis of electrical states, but on the basis of quantum mechanical states. Important in quantum mechanics is the superposition principle and quantum entanglement. There are already theoretical studies that show that certain computer science problems can be solved much more efficiently by exploiting quantum mechanical effects than is comparatively the case with a classical computer. For example, the search in really extremely large databases can function particularly efficiently and the factorisation of large numbers can also be carried out more quickly. This makes it possible to reduce the calculation time of many mathematical and physical problems quite significantly. So far, however, the quantum computer is a predominantly theoretical concept and there have been various proposals for its realisation. However, quantum computers have already been tested on a small scale in the laboratory. At first, these had only a few qubits. The biggest success to date is 65 qubits for the processor, which was set as a record in August 2020. Not only the number of qubits is decisive for success, a low error rate for computing and reading is also important, as is the time for which qubits can be maintained without errors.

## Where can quantum computers be used?

In principle, quantum computers can perform all the calculations of conventional computers, but there are particular strengths where classical supercomputers have particular difficulties due to their complexity. For example, quantum computers succeed above all in optimisation tasks in finance and logistics and in simulations of new chemical substances for advanced biotechnology and the development of medicines and in the development of new types of accumulators. Quantum computers can also be used helpfully in cryptography. Such a quantum computer is also advantageous in energy optimisation.

A hybrid computer consisting of a quantum computer and a conventional computer can also be used in a VW navigation system. Such a quantum computer is already said to exist with 2048 qubits.

## What are the difficulties with quantum computers?

Quantum computers require complex cooling to function properly and are therefore not available for the consumer market for the foreseeable future. However, research will already be able to benefit from such computer systems in the medium term. There are numerous simulations that can be made with the help of quantum computers.

## How expensive is quantum computing?

The special flagship of Germany's technology location is the first quantum computer. This one costs 11,621 € monthly rent. The computer has a total of 27 qubits and is stable enough for industrial operation. IBM is planning a quantum computer with more than 1,000 qubits by 2023.