Modelling shows which quantum systems are suitable for quantum simulations
Ultracold atoms in an optical lattice have been considered for quantum simulation. © arö/HZB
A joint research group led by Prof. Jens Eisert of Freie Universität Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems. This is done with the help of complex solid state systems that can be studied experimentally. The study was published in the renowned journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).
"The real goal is a robust quantum computer that generates stable results even when errors occur and corrects these errors," explains Jens Eisert, professor at Freie Universität Berlin and head of a joint research group at HZB. So far, the development of robust quantum computers is still a long way off, because quantum bits react extremely sensitively to the smallest fluctuations in environmental parameters.
New approach
But now a new approach could promise success: two postdocs from the group around Jens Eisert, Maria Laura Baez and Marek Gluza have taken up an idea of Richard Feynman, a brilliant US-American physicist of the post-war period. Feynman had proposed to use real systems of atoms with their quantum physical properties to simulate other quantum systems. These quantum systems can consist of atoms strung together like pearls in a string with special spin properties, but could also be ion traps, Rydberg atoms, superconducting Qbits or atoms in optical lattices. What they have in common is that they can be created and controlled in the laboratory. Their quantum physical properties could be used to predict the behaviour of other quantum systems. But which quantum systems would be good candidates? Is there a way to find out in advance?
Finding good candidates
Eisert's team has now investigated this question using a combination of mathematical and numerical methods. In fact, the group showed that the so-called dynamic structure factor of such systems is a possible tool to make statements about other quantum systems. This factor indirectly maps how spins or other quantum quantities behave over time, it is calculated by a Fourier transformation.
Bridging the gap
"This work builds a bridge between two worlds," explains Jens Eisert. "On the one hand, there is the Condensed Matter Community, which studies quantum systems and gains new insights from them - and on the other hand there is Quantum Informatics - which deals with quantum information. We believe that great progress will be possible if we bring the two worlds together," says the scientist.
- Shedding light on insulators: how light pulses unfreeze electronsMetal oxides are abundant in nature and central to technologies such as photocatalysis and photovoltaics. Yet, many suffer from poor electrical conduction, caused by strong repulsion between electrons in neighboring metal atoms. Researchers at HZB and partner institutions have shown that light pulses can temporarily weaken these repulsive forces, lowering the energy required for electrons mobility, inducing a metal-like behavior. This discovery offers a new way to manipulate material properties with light, with high potential to more efficient light-based devices.
- Lithium-sulphur batteries with lean electrolyte: problem areas clarifiedUsing a non-destructive method, a team at HZB investigated practical lithium-sulphur pouch cells with lean electrolyte for the first time. With operando neutron tomography, they could visualise in real-time how the liquid electrolyte distributes and wets the electrodes across multilayers during charging and discharging. These findings offer valuable insights into the cell failure mechanisms and are helpful to design compact Li-S batteries with a high energy density in formats relevant to industrial applications.
- Self assembling monolayer can improve lead-free perovskite solar cells tooTin perovskite solar cells are not only non-toxic, but also potentially more stable than lead-containing perovskite solar cells. However, they are also significantly less efficient. Now, an international team has succeeded in reducing losses in the lower contact layer of tin perovskite solar cells: The scienstists identified chemical compounds that self-assemble into a molecular layer that fits very well with the lattice structure of tin perovskites. On this monolayer, tin perovskite with excellent optoelectronic quality can be grown, which increases the performance of the solar cell.