Roee Ozeri
Quantum metrology is a science investigating the limits imposed by quantum mechanics on the precision with which measurements can be carried out. By using methods borrowed from quantum information science and coherent control precision limits can be pushed further. Multiple methods have been developed in the context of Quantum Computation to extend the time over which quantum superpositions remain coherent. While negating the effect of noise, all these methods allow for the application of quantum gates in their logic subspace. Desirably, logical qubit dynamics is induced by operators which have minimal overlap with the noise in the environment. Many such methods, including Dynamic Decoupling (DD) protocols, Decoherence Free Subspaces (DFS), and Quantum Error Correction Codes (QECC), were demonstrated experimentally in several systems, including trapped ions. The successful implementation of these methods is in some sense boring – they were designed to be successful. Their failure (and they all fail at some point) is interesting. That is because it exposes a very small and subtle part of the environment: that which overlaps with the qubit logical operations. This part of the environment is normally masked by the much larger noise background. In this talk I will review the application of the methods above in trapped-ion qubit arrays. Examples include the use of DD for precision magnetometry and light-shift spectroscopy. The use of a two qubit DFS for the measurement of the magnetic interaction between two electronic spin at a micrometer-scale distance, and the use of repetitive QECC for Heisenberg-limited metrology.