ancilla

noun

1. (rare)A maid.

   “‘And pass me that towel,’ added Ada, but the ancilla was picking up coins she had dropped in her haste […]”

2. An auxiliary or accessory

   “The filter achieves this two-qubit filtering effect by using two ancilla photons as probes that detect whether or not the two input photons are in the desired states.”

3. An ancilla bit

   “The circuit uses a single ancilla for each stabilizer generator.”