Oral:Optimizing Dynamical Decoupling Sequence Using Real-Time Noise Sensing.*

Nitrogen Vacancy (NV) Centers are a promising candidate for the implementation of quantum technologies.  This is partly due to the high coherence times of the nuclear spin, even at room temperature, that can be extended with dynamical decoupling (DD). However, in an experimental setting the noise can fluctuate and to accommodate for that we can use the electron spin in NV center as a spectator qubit. This choice is motivated by the contrasting gyromagnetic ratio of the electrons corresponding to the spectator qubit, with the very low gyromagnetic ratio of nuclei corresponding to the memory qubit. The dynamics of the spectator qubits are therefore much faster than the memory qubits. By using Coherent Population Trapping (CPT), a Λ-type system trapped in the dark-state can be used to sense the noise in real-time. The noise causes a non-zero population of the excited state, leading to photon emission. The time series of the photon emissions has been used to sense the noise in real-time^[1]. We use this to obtain a probability distribution of the characteristic time of the noise. Consequently, we show that the optimal time between two DD pulses (τ) can be determined analytically. By continuously updating τ, we can actively tailor the pulse sequence in order to have a longer coherence time.