Quantum computers are able to deal with large problems, like molecular modelling, financial prediction and cryptography. A classical controller is used to control the qubits of the quantum computer. A proposed controller, operating at 4K, needs a clean voltage supply in order to function well. The long interconnects between the room temperature power supplies and the 4K classical controller are not loss-less and do have parasitic capacitance and inductance. Low drop-out (LDO) voltage regulators are able to clean this dirty supply voltage and produce a stable, regulated voltage. Therefore, a cryogenic 40nm CMOS LDO voltage is designed. This regulated is designed with room temperature models and optimized for operating at 4K. The specification are competitive to other LDO voltage regulators.