Okay, so I’ve heard qubits and qutrits, but until recently hadn’t heard ququarts. More googling revealed qupents. Okay, then after a little more research I found an old 1999 paper which, while not containing a six level quantum system, did contain,
In particular, our protocol transfers entanglement from a pair of quantum correlated
light fields to a pair of trapped atoms in a process of quantum state exchange, or qusex.
Ahem.