Entanglement is used for faster-than-light data transmission using a one-to-one transmitter and receiver.
Culture entanglement technology of the 29th century CE had a transmission range of at least 3500 light years. There was also a probability of greater than 2% that the receiver would fail to collapse, resulting in total transmission failure. The high rate of failure meant entanglement was only used in extreme emergencies.
- Quantum entanglement at Wikipedia.