  The low frequency region of the spectrum is a challenging regime for quantum
probes. We support the idea that, in this regime, performing Ramsey
measurements carefully controlling the time at which each measurement is
initiated is an excellent signal detection strategy. We use the Fisher
information to demonstrate a high quality performance in the low frequency
regime, compared to more elaborated measurement sequences, and to optimise the
correlated Ramsey sequence according to any given experimental parameters,
showing that correlated Ramsey rivals with state-of-the-art protocols, and can
even outperform commonly employed sequences such as dynamical decoupling in the
detection of low frequency signals. Contrary to typical quantum detection
protocols for oscillating signals, which require adjusting the time separation
between pulses to match the half period of the target signal, and consequently
see their scope limited to signals whose period is shorter than the
characteristic decoherence time of the probe, or to those protocols whose
target is primarily static signals, the time-tagged correlated Ramsey sequence
simultaneously tracks the amplitude and the phase information of the target
signal, regardless of its frequency, which crucially permits correlating
measurements in post-processing, leading to efficient spectral reconstruction.
