How can you answer correctly without knowing what the question was? The quantum RAM and its use in the QPQ protocol.

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.