Entanglement-assisted quantum metrology

Understand

Entanglement-assisted quantum communication employs pre-shared entanglement between sender and receiver as a resource.

• We apply the same framework to quantum metrology, introducing shared entanglement between the preparation and the measurement stage, namely using some entangled ancillary system that does not interact with the system to be sampled.
• This is known to be useless in the noiseless case, but was recently shown to be useful in the presence of noise.
• Here we detail how and when it can be of use.