There’s a Lot to Topological Materials and the Application to Quantum Computing

Randomized measurements reveal topological quantum states

Key points…

+  Topological materials – materials that have surface properties very different to those found in their bulk – are currently revolutionizing condensed-matter physics thanks to their unique characteristics. Researchers in Austria, France, the US and Germany have now put forward a new technique to identify and characterize the global invariants that mathematically describe these materials in various experimental platforms in the laboratory. The work could advance our understanding of these structures, which might be used in next-generation energy-efficient electronics and quantum computing applications.

+  Topological materials show similar geometries on the molecular scale, which gives rise to several unusual mechanical and electrical properties. Topological insulators, for example, do not carry electrical currents in their bulk, but current does flow along their surfaces through special “edge” states. Crucially, the electrons in these states can only travel in one direction, and they also steer around imperfections or defects on the surface without backscattering. Since backscattering is the main energy-dissipating process in electronic devices, these “topologically-protected states”, as they are known, might be useful ingredients in next-generation energy-efficient devices.

+   Random operations

+  The experimental recipe consists of subjecting a quantum state to a number of different random operations and studying how it reacts, Vermersch says. “By then using random matrix theory, we have proven that we can estimate MBTIs from this data set obtained from such randomized measurements.”

+  The specific feature of this technique is that although the topological invariants are highly complex, non-local correlation functions, they can still be extracted from statistical correlations of randomized measurements, he adds. Such random measurements are possible in synthetic quantum matter (or “quantum simulators”) made from tried and trusted experimental platforms such as cold atoms, trapped ions and superconducting quantum bits, to name but three. “Our protocol for measuring the topological invariants can be therefore be directly studied in these existing systems in the laboratory,” says Vermersch.

Source:  physics world.  Isabelle Dume,  Randomized measurements reveal topological quantum states…

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