# The theory of entanglement-assisted quantum metrology

### APA

Zhou, S. (2020). The theory of entanglement-assisted quantum metrology. Perimeter Institute. https://pirsa.org/20020060

### MLA

Zhou, Sisi. The theory of entanglement-assisted quantum metrology. Perimeter Institute, Feb. 12, 2020, https://pirsa.org/20020060

### BibTex

@misc{ pirsa_PIRSA:20020060, doi = {10.48660/20020060}, url = {https://pirsa.org/20020060}, author = {Zhou, Sisi}, keywords = {Other}, language = {en}, title = {The theory of entanglement-assisted quantum metrology}, publisher = {Perimeter Institute}, year = {2020}, month = {feb}, note = {PIRSA:20020060 see, \url{https://pirsa.org}} }

Sisi Zhou Perimeter Institute for Theoretical Physics

## Abstract

The quantum Fisher information (QFI) measures the amount of information that a quantum state carries about an unknown parameter. Given a quantum channel, its entanglement-assisted QFI is the maximum QFI of the output state assuming an input state over the system and an arbitrarily large ancilla. Consider N identical copies of a quantum channel, the channel QFI grows either linearly or quadratically with N asymptotically. Here we obtain a simple criterion that determines whether the scaling is linear or quadratic. In both cases, we found a quantum error correction protocol achieving the channel QFI asymptotically and an SDP to solve the optimal code.