Our new paper shows how near-term quantum computers can be used to simulate excited states of molecules.
While low-depth quantum algorithms, such as the Variational Quantum Eigensolver (VQE), have been used to determine ground state energies, methods for calculating excited states currently involve high-depth circuits or a large number of additional samples. Our new algorithm makes use of a technique called overlap estimation to simulate excited states much more efficiently, and we show how it can be implemented using a low-depth circuit on small quantum computers available now or in the near future. Our algorithm can be applied more generally, for example to enhance principal component analysis, which has found applications in bioinformatics, neuroscience, image processing and quantitative finance. Click here to read the paper in full!