Abstract
Weak measurement (WM) with state pre- and post-selection can amplify otherwise undetectable small signals and thus has potential in precision measurement applications. Although frequency measurements offer the hitherto highest precision due to the stable narrow atomic transitions, it remains a long-standing interest to develop new schemes to further escalate their performance. Here, we demonstrate a WM-enhanced correlation spectroscopy technique capable of narrowing the resonance linewidth down to 0.1 Hz in a room-temperature atomic vapour cell. The potential of this technique for precision measurement is demonstrated through weak magnetic-field sensing. By judiciously pre- and post-selecting frequency-modulated input and output optical states in a nearly orthogonal manner, a sensitivity of 7 fT Hz−1/2 at a low frequency near DC is achieved using only one laser beam with 15 µW of power. Additionally, our results extend the WM framework to a non-Hermitian Hamiltonian and shed new light on metrology and bio-magnetic field sensing.
Highlights
Weak measurement (WM) with state pre- and post-selection can amplify otherwise undetectable small signals and has potential in precision measurement applications
Contrary to this strong procedure, the notion of weak measurements (WMs) introduced by Aharonov et al.[1] describes an intriguing situation where partial information is gained by feebly probing the system without undermining its initial state
Precision frequency measurements based on atomic transitions lie at the heart of many precision measurements, including atomic clocks[19] and optical magnetometry[20]
Summary
Weak measurement (WM) with state pre- and post-selection can amplify otherwise undetectable small signals and has potential in precision measurement applications. This D value corresponds to an HWHM of ~1 Hz for the g(2)(0) profile, which is much smaller than the power-broadened EIT resonance linewidth of 13 Hz. The optimization of D for the best B sensitivity turns out to be a trade-off between L and SNR: a smaller L requires a larger D, but a larger D aggravates the effect of the laser intensity noise on the g(2)(0) value and results in a drastic reduction of the SNR, as explained in the previous subsection.
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