Quantum metrology with time-dependent Hamiltonians*

I will give an overview of recent results [1,2,3] in generalizing the theory of quantum metrology to the situation when the Hamiltonian is time dependent. In the general case, optimal precision requires coherent control of the system, together with adaptive feedback. When these ingredients are combined, we will show that existing bounds for the precision using time-independent Hamiltonians can be broken. Application to precisions frequency measurements will be discussed.

[1] S. Pang, A. N. Jordan, Nature Communications 8, 14695 (2017)
[2] J. Yang, S. Pang, A. N. Jordan, Phys. Rev. A 96, 020301(R) (2017)
[3] A. N. Jordan, Science 356, 802 (2017)