We report on the 'QUantum-Enhanced Space-Time experiment' (QUEST), and its successor 'SPI-QG' which consist of co-located Michelson interferometers with the ultimate goal of searching for signatures from quantization of space-time. We performed a first engineering run with QUEST which already sets new upper limits for stochastic gravitational waves in the range 13 to 80 MHz -- an auxiliary result from the fact that our experiment also resembles a table-top scale gravitational-wave detector. We also report on the future version of this experimental paradigm, SPI-QG, in which we plan to employ single-photon detection readout on a larger-scale set of Michelson interferometers with 7.5m long folded arms. SPI-QG stands for 'Single-Photon detection Interferometry for Quantum Gravity'. In this version of the experiment, single photon readout is expected to increase sensitivity to stochastic signals, such as from quantization of space-time. With this we should be able to test existing predictions of quantized space-time signatures.