Study: How Powerful Are Quantum Computers Really?

Until now, data is processed and stored in the classical way – this also applies to all processes that take place in the quantum world. For example, as soon as the quantum state of a photon is measured, the information about it is available in classical form. The question therefore arises whether it is not better to capture such quantum information – for example from molecules or magnetic fields, which “live” in this quantum world – with quantum sensors, to process it with quantum computers and only at the very last minute to return the result to the classical – to shape – that we can grasp.

Google announced big breakthrough in 2019
Scientists around the world are working on various solutions for the realization of such quantum sensors and quantum computers. In 2019, a team from Google Quantum AI – see video – reported in “Nature” magazine that with its 53 quantum bits (qubits) “Sycamore” quantum processor, which is based on superconducting circuits, the desired superiority of quantum computers over the fastest classical computers ( “quantum supremacy”).

How many different tasks are already being processed on the already available quantum processors – “the problem is always that you first have to split a task from the macroscopic level to the quantum level to run it on the quantum computer. And at the end I have to read out the result and bring it back to the macroscopic level,” explains Richard Küng of the Institute for Integrated Circuits at the University of Linz, who is co-publishing the current publication with colleagues from the California Institute of Technology. (Caltech) and Google Quantum AI.

Exploring the benefits of quantum data
Instead of going through this bottleneck twice, the scientists looked at whether it is an advantage to stay in the quantum world for data processing and process quantum mechanical data on the quantum computer, so without information “translation”. To do this, they devised three hypothetical experiments in which – similar to the game “Mastermind” – the goal is to crack a code.

Such a task is usually solved by performing an experiment (with “Mastermind” starting with a random set of colored pencils), receiving data (with “Mastermind” the information whether the colors and positions of the pencils are correct or whether the pencils have the right suit but have the wrong position) and evaluate them (if the task requires it, with a supercomputer) until you get a result.

However, if it is not about classical information (such as the color and location of a playing piece), but about quantum information (such as the state of a molecule) and if you have a quantum computer, you can work in a completely different way: You do not have to directly measure and translate data in the classical world, but can leave the information in the quantum world and process it with quantum memory and quantum processor.

“With the hardware available today (Google’s ‘Sycamore’ quantum chip, note) we were able to mathematically prove based on concrete problems that there really is a difference and that quantum computers can learn from exponentially less experiments and data than conventional ones. strategy,” says Küng. Specifically, with 40 qubits, the researchers have shown that an exponential quantum advantage is possible with the currently available quantum processors.

The computer scientist sees the potential of this information processing at quantum level mainly in problems of a quantum mechanical nature. As examples he cites photosynthesis, which is still not understood because of the quantum effects that occur, the design of new pharmaceutical active ingredients, where quantum mechanical effects are also important, or protein folding.