The new method for determining the quantum state in quantum simulators reduces the number of necessary measurements and makes work with quantum simulators much more efficient.
In a few years, a new generation of quantum simulators could provide insights that would not be possible using simulations on conventional supercomputers. Quantum simulators can process a great amount of information since they quantum mechanically superimpose an enormously large number of bit states. For this reason, however, it also proves difficult to read this information out of the quantum simulator. To be able to reconstruct the quantum state, a very large number of individual measurements are necessary. The method used to read out the quantum state of a quantum simulator is called quantum state tomography. "Each measurement provides a 'cross-sectional image' of the quantum state. You then put these cross-sectional images together to form the complete quantum state," explains theoretical physicist Christian Kokail from Peter Zoller's team. The number of measurements needed in the lab increases very rapidly with the size of the system. "The number of measurements grows exponentially with the number of qubits," the physicist says. The Innsbruck researchers have now succeeded in developing a much more efficient method for quantum simulators.
For more information see:
Entanglement Hamiltonian Tomography in Quantum Simulation. Christian Kokail, Rick van Bijnen, Andreas Elben, Benoit Vermersch, and Peter Zoller. Nature Physics 2021. doi: 10.1038/s41567-021-01260-w https://www.nature.com/articles/s41567-021-01260-w