Bridging the quantum universe and classic world

Quantum computers have the potential to achieve performance and speed far beyond current HPCs.

However, as Professor Mario Ruben of the Karlsruhe Institute of Technology (KIT) points out, such machines would also be quite susceptible to external interferences – with information flow in and out of the system ranked as a “critical” point.

Fortunately, KIT researchers managed to successfully “read out” the quantum state of an atom directly – simply by using electrodes. 

“Normally, every contact with the outer world changes information in a quantum mechanical system in a completely uncontrolled manner,” explained Ruben.

“We therefore have to keep the quantum state stable and shielded. On the other hand, information has to be read out in a controlled manner for further use.” 

According to Ruben, magnetic molecule complexes may present a possible solution as a metal atom with a pronounced magnetic moment – or “spin” – is located in its complex center. Interestingly, the spin is surrounded by organic molecules that shield the atom.

“When synthesizing this protective enclosure, we can exactly define how much the metal atom sees of the outer world,” said the scientist.

The above-mentioned research is based on a metal atom terbium that was provided with an enclosure of about 100 carbon, nitrogen, and water atoms and subsequently placed in the center of nanometer-sized, electric gold contacts.

Due to the properties of the molecule, the electrodes had an effect similar to the three channels of a transistor. Electric voltage of the middle gate electrode influenced the current through the other two electrodes. 

In this way, the working point was set. Then, the molecule was exposed to various changing magnetic fields and the jump of the spin was reflected by the amplitude of the current curve. 

“By measuring current flow, we found that the nuclear spin of the metal atom is stable for up to 20 seconds… For quantum mechanical processes, this is [actually] a very long time.” 

Ruben says he is confident the results will be of particular importance to spintronics and quantum computing. 

“Spintronics uses the magnetic spin of single particles for information processing. The word describes the symbiosis of spin and electronics. Quantum computers use quantum mechanical effects, such as the entanglement and super-position of spins, for the parallel execution of algorithms at high speed,” he added.