This Ph.D. project involves searches for hidden sector dark matter, including QCD axions and axion like particles (ALPs). Our group at Sheffield leads the 'Quantum Sensors for the Hidden Sector' collaboration, and collaborates with the Axion Dark Matter Experiment (ADMX) collaboration in the USA. A Ph.D. in this area would involve elements of detector simulation, lab based characterisation of detectors and detector parts, instrumentation design and operation, characterisation of microwave electronics both at cryogenic temperatures (to 10mK) and at room temperature, and data analysis. Teamwork with other members of the QSHS collaboration and with ADMX will be important. The QSHS collaboration consists of scientists at Cambridge, Oxford, Lancaster, RHUL, NPL, UCL and Liverpool, as well as Sheffield. The ADMX collaboration have their current experimental apparatus at The University of Washington, Seattle, with other active groups at Fermilab, The University of Florida (Gainseville), Lawrence Livermore National Lab, and on other U.S. based campuses.