A quantum simulator of impossible physics

The research group Quantum Technologies for Information Science (QUTIS) of the UPV/EHU-University of the Basque Country, led by the Ikerbasque professor Enrique Solano, in collaboration with an experimental group of the University of Tsinghua (Beijing, China) led by professor Kihwan Kim, has created a quantum simulator that is capable of creating unphysical phenomena in the atomic world, in other words, impossible physical phenomena. The researchers in the two groups have succeeded in getting a trapped atom to imitate behaviours that contradict its own fundamental laws, thus taking elements of science fiction to the microscopic world. "We have managed to get an atom to act as if it were infringing the nature of atomic systems, in other words, quantum physics and the theory of relativity. It is just like what happens in the theatre or in science fiction films in which the actors appear to display absurd behaviours that go against natural laws; in this case, the atoms are obliged to simulate absurd actions as if an actor in the theatre or in science fiction were involved," explained Prof Solano.

The results of this research have been published in the journal Nature Communications, in the article "Time reversal and charge conjugation in an embedding quantum simulator." The research team of the UPV/EHU's QUTIS group has been led by Prof Enrique Solano and has had the participation of Dr Lucas Lamata and Dr Jorge Casanova, currently at the University of Ulm, Germany.

In this experiment the researchers reproduced in the lab the theoretical proposal previously included in a previous piece of research led by the QUTIS group; it describes the possibility that a trapped atom can display behaviour that is incompatible with the fundamental laws of quantum physics. More specifically, we are talking about operations prohibited in microscopic physical systems, such as charge conjugation, which transforms a particle into an antiparticle, or time reversal, that reverses the direction of the time arrow.

To conduct the experiment it was necessary to use a charged atom trapped by means of electromagnetic fields under the action of an advanced laser system. We could describe symmetry operations of this type as prohibited ones, as they could only exist in a universe that is different from the one we know and governed by different laws. Yet in this experiment it has been possible to simulate the realisation of this set of impossible laws in an atomic system.

The UPV/EHU's QUTIS group is a world leader in quantum simulation and its influential theoretical proposals are often verified in the most advanced quantum technology laboratories. In this case, physical operations that are prohibited for the atomic world can be reproduced just as in science fiction, in other words, just as if they were taking place artificially in a quantum theatre.