Spectral decomposition and high-accuracy Greens functions: Overcoming the Nyquist-Shannon limit via complex-time Krylov expansion
The method overcomes the Nyquist-Shannon limit in computing low-energy spectra of quantum systems by augmenting time series with complex-time Krylov states. This technique allows for arbitrary frequency resolution, significantly improving accuracy for Green's functions even in two-dimensional models where standard Fourier transforms fail.