Prof. Linnhoff, in which industries can quantum computing offer added value in a timely manner?
Prof. Dr. Claudia Linnhoff-Popien: For this, we must first talk about timely application areas. I count simulations, optimizations and artificial intelligence among them. Let's stay with optimization. Here, you can take virtually any task that has to do with combinatorial optimization to a fast quantum advantage. So I consider a large set of discrete elements, select from it a subset that satisfies constraints and is to be optimized with respect to a cost function.
Can you illustrate this with a practical example?
Prof. Dr. Claudia Linnhoff-Popien: Let's look at the optimization of transport routes. Let's take a truck with five large pallets to be delivered to five cities. For five different cities, the set of discrete elements is the set of all conceivable routes five factorial. So that's five times four times three times two possible routes. So I have 120 different routes how the truck can leave the different cities. From this I select a subset. The simplest subset is a set of ones, because I want to determine exactly one recommended route.
In addition, this route should satisfy constraints. This is the distance between two cities, which adds up to the total length of the route to be taken. To determine the shortest route, this route must be minimal with respect to a cost function (gasoline, time, wear and tear) - this is a classic example of combinatorial optimization.
And this is where the quantum computer comes into play?
Prof. Dr. Claudia Linnhoff-Popien: Right! Because the classical computer would now calculate the length of all 120 routes one after the other to determine the shortest distance. That still sounds simple now. However, this calculation becomes very complex as soon as we increase the number of cities to, say, 50 cities. With a good 50 cities, we have more routes (50 factorials) than there are atoms in the entire universe. No classical computer will ever be able to compute 50 different cities with all conceivable possible routes. A quantum computer, however, requires only one computational operation to do so - an incredible advantage for this type of problem.
And now the question is, "How can this benefit be translated to a practical application?" Let's look at the factory of the future, where robotic arms will be used. There, for example, the question arises, "What is the shortest route that the robotic arm, which has to weld five points in succession, chooses on a workpiece?"
Another example would be portfolio optimization in finance. On which positions (funds, shares, tangible assets, etc.) do I divide my money in order to get the greatest possible return or the greatest possible security?
Or an example from drug research: which different active ingredients do I have to combine with each other in order to get a desired effect (drug, vaccine, etc.) and minimize side effects? Where is the optimum?
As you can see, the possible applications are not limited to one industry - the areas of application for quantum computing are cross-sectoral and offer enormous potential for the economy.
Accessibility
Language
