Quantum sensing technologies have been improving rapidly in recent years. The high sensitivities achievable will enable searches for very small signals from dark matter and gravitational waves. I will discuss two separate projects as examples. We propose a new way to use trapped atoms as atomic clocks combined with astrophysical proof masses to search for gravitational waves. Unlike previous detectors, this technology should enable searches in the very low frequency band between roughly 10^-6 and 10^-4 Hz, in the gap below satellite-based detectors such as LISA and above pulsar timing arrays. I will also discuss the use of trapped ion technology for dark matter direct detection. In particular the recent advances in ion trapping, partially motivated by quantum computation, has led to sensors capable of detecting millicharged dark matter and possibly axions and hidden photons as well.