In contrast to classical bits, quantum bits can assume two states simultaneously: right and left, yellow and blue, zero and one © KIT

Cyclones, traffic congestion, demographic development; if one wants to predict the effect of such events, computer simulations provide important services. However, many processes in nature are so complicated that conventional computers fail to calculate. Here, researchers place great hopes in quantum simulators. One of the most fundamental natural phenomena is the interaction between light and matter in photosynthesis. Physicists at the Karlsruhe Institute of Technology (KIT) have now taken a major step towards the quantum mechanics understanding of plant metabolism. They report this in the journal Nature Communications.

“A quantum simulator is a precursor of the quantum computer. In contrast to this, he is not able to carry out any calculations, but is designed to solve a specific problem, “says Jochen Braumüller of the KIT Physical Institute. Since the high efficiency of the process of material and energy conversion, which the plants carry out with light, can not be fully understood with classical physical theories, researchers such as Braumüller have drawn on the quantum model. Together with scientists from the Institute for Theoretical Solid-State Physics (TFP) he showed for the first time in the experiment that quantum stimulations of the interaction between light and matter as a basis of photosynthesis and thus the basis of our life function.

The interaction between light and matter in photosynthesis – for example when sunlight hits a leaf – can be described at the microscopic level as the interaction of the photons of light with the atoms of matter. The high efficiency of this mechanism of almost 100 percent suggests that it is subject to the rules of quantum physics, which is difficult to simulate with classical computers and simple bits. For this, information is represented by a switch which can store information as 0 or 1. Quantum bits, on the other hand, are characterized by the fact that during the simulation they can assume states 0 and 1 simultaneously following the quantum-physical rules.

Braumüller and his co-authors have now developed one of the first functional building blocks for a quantum simulator of the light-matter interaction: superconducting circuits represent the atoms, thus the matter, and electromagnetic resonators the photons, ie the light. The physicists were thus able to produce an effect in which both the quantum bit and the resonator were simultaneously in two opposing states. “Qubit and resonator are intertwined,” says Michael Marthaler of the TFP of KIT. “This is also the reason for the exponentially improved computing power, compared to classical computers.” With the fulfillment of this basic principle of quantum mechanics, the researchers have now shown the feasibility of analog quantum stimulation with superconducting circuits.

As a next step, they want to expand their system with many other building blocks. “A classical simulation of this extended system would take longer than the age of the universe,” says Martin Weides, who has been a group leader at the KIT Physical Institute since 2015. If the planned quantum mechanics simulation is “a milestone on the way to the universal quantum computer.”

Source: KIT