Quantum computers are a revolutionary new type of computer that can do much more than classical computers – if you know how to use them properly. The exhibit illustrates a major difference between quantum and classical computing – the principle known as superposition. 

Classical computers use bits (whose value is either 0 or 1) to represent numbers. Quantum computers, on the other hand, use “qubits”, which can have a value of 0 and 1 at the same time. This means that quantum computers can perform simultaneous calculations involving millions of numbers whilst a classical computer can only work with one number at a time.

Almost Like Magic

By contrast, a quantum computer is like a magical coin, which can show one of its sides but also a state between them: Half Tony and half Samantha, for example. You can see both of them on the coin in our exhibit if you don’t look through the filter.

This state between 0 and 1 is referred to as “superposition”. So a qubit can be in a superposition state, representing both the value 0 and the value 1 simultaneously. It doesn’t collapse into a certain state and take on the value 0 or 1, Samantha or Tony, until we measure it. If you look at our exhibit through the filter and turn the filter, that is exactly what you will see: Only one of the two is visible.

Superbrain

Superposition enables quantum computers to perform numerous different calculations in parallel. Imagine, for example, if you could add lots of pairs of numbers all at the same time and see all the results without actually having to go through every single addition. That’s the kind of brain power that superposition offers in quantum computing.

It is important to note that superposition is a complex concept that is not easy to visualize. Quantum physics, which quantum computing is based on, is a sophisticated science. In essence, though, superposition merely means quantum bits can take on multiple states at the same time and are not limited to one single number.

Large simulations on quantum systems are not yet possible in the current phase of quantum computing. However, new research findings show that quantum systems allow special computation methods that do not work well on standard hardware but are very efficient on quantum computers.

Our aim is to integrate these new methods into simulations and make SimTech one of the first simulation research centers to explore the use of quantum computers.

New Opportunities–New Challenges

Algorithms for simulations on high-performance computers are optimized for current hardware. But quantum computing is different because it completely changes the efficiency of standard operations. A number of complex problems can be solved much more quickly or precisely on quantum systems, thus challenging best practices in algorithm design.

Quantum computers work with qubits. Unlike conventional bits, qubits can store 0 and 1 information at the same time. That means they exist where the two states overlap: a principle scientists refer to as “superposition”.

The more numbers to be represented, the more advantageous qubits are. Two numbers (0 and 1) can be represented simultaneously using one qubit, four numbers (00, 01, 10, 11) using two qubits and 1024 numbers using 10 qubits.

Modifying for More Advantages

To solve problems effectively on quantum computers, we need to adjust our computation paths to qubit characteristics. This modification process has revealed that quantum computers offer advantages in fields such as cryptography, quantum physics, and quantum chemistry.

The benefit of using quantum computers for cryptography purposes is self-evident. In one computation step, we can try considerably more (2ⁿ as many more with n qubits) codes than with conventional computers. It is also possible that quantum physics and quantum chemistry problems could be simulated effectively on quantum computers as they are, after all, based on exactly the same physical principles. 

But when it comes to things like solving large equation systems, for flow rates around a heat pump for instance, there are three questions we need to answer: 

1. What changes do we have to make to our calculation sequences (or, indeed, the entire computation path) to exploit qubits’ ability to process two states simultaneously and to be entangled?
2. How do we get our input data into the quantum computer and the calculated result back out?
3. How do we deal with the instability of qubits, i.e. the fact that they change state over time even without us actively performing computations to make the changes?

We know lots of measurements are needed to get all the results for question 2 because the qubits collapse into a 0 or 1 state each time they are measured, which means we can only measure one of the many numbers present each time.

So we are considering which parts of our calculations would actually be suitable for quantum computers, could be performed quicker than on conventional computers, and how we can obtain reliable and not completely random results. After all, it would be nice to be sure whether that delicately designed bridge will actually be stable, that plane will be safe to fly, that predicted implant expiry date is right, or whether we are just being duped by unstable qubits.