I will present some methods to access any quantum superposition of memory cells in an array of (classical or quantum) memory cells. This is a quantum-coherent version of the random access memory (RAM) that is present in any computer. I will then describe its use for the QPQ protocol: It is a quantum cryptographic primitive that allows a user to retrieve an item from a database in possession of another user, without revealing which item she retrieved. If the database owner tries to obtain information on the query, the person querying the database can find it out. The protocol ensures also data privacy of the database.