What do we need quantum computers for? Aren't todays computers not powerful enough? - Although computing power is constantly increasing, big mathematical models such as weather simulation or algorithms for traffic flow optimization quickly reach their limits with existing computing capacities. As a matter of fact, quantum computers can actually process enormous amounts of data. For example, a quantum computer could (at least in theory) process the movement data of all vehicles in a city in such a way that traffic light changes, average speeds of all vehicles in the model and other exogenous and endogenous factors could be taken into account in a mathematical model in such a way that each vehicle would be guided along optimized routes to avoid traffic jams - and even the calculated time of the arrival would be much more accurate than today's estimates.
What distinguishes the quantum computer from today's computers? - First, today's computers are based on the binary logic of 0 and 1 (current flows, current does not flow). Although the quantum computer also knows the "bit", the bit of a quantum computer can assume ALL states between 0 and 1; this is called quantum bits or qubits. The state between 0 and 1 is called superposition. Second, these so-called qubits can be interconnected with each other, i.e. the behavior of one qubit influences the behavior of the qubit it is connected with. The rule of thumb is: The more qubits are entangled with each other in a quantum computer, the more computing power. The highest number of entangled qubits has so far been achieved by the company Google, with 72 qubits.
In order to fully exploit the potential of quantum computing in practice, a lot of research is still needed: there are still numerous challenges to be solved. For example, it is only possible to keep the superposition state of a qubit stable for around 100 milliseconds. And even for this an enormous effort is required. Quantum computers in research laboratories are as large as mainframe computers in the early days of computing.