The main purpose of this White Paper is to summarise for a general audience the current status of quantum cryptography implementation security and to outline the current understanding of the best
practice related to it. We will illustrate the discussion with Quantum Key Distribution (QKD), although many of the arguments also apply to the other quantum cryptographic primitives. It is beyond the scope of this paper to analyse the security of all QKD protocols. To maintain readability, we will outline how the physical implementation may impact security but will not provide a detailed theoretical analysis. For the latter, we refer the reader to the references cited in the paper.