Spectroscopy: Shifting light with spin

Frank K. Wilhelm

J. Delpy, S. Liu, Pascal Neveu +3 more

A light-induced nonequilibrium regime is introduced in the standard spin noise spectroscopy, in which the laser light plays the role of both the probe beam and a driving field. The effect of the induced coherences is experimentally and theoretically demonstrated to be a splitting in the spin noise spectrum, which originates from and allows for the measurement of light shifts experienced by the atomic levels.

Yuehua Pang, Yi Shen, Jiahao Huang +1 more

Ramsey spectroscopy serves as a key tool for frequency measurement. Although entanglement can enhance the measurement precision, the atom-atom interaction required for entanglement generation may lead to a frequency shift. In addition, the spectra also suffer from light shift caused by the interaction between light and atoms. Thus, it is difficult to achieve high precision without inducing additional systematic errors. Here, we propose to realize high-precision entanglement-enhanced Ramsey spectroscopy with composite pulses. First, we utilize spin-squeezed states generated by one-axis twisting (OAT) dynamics to enhance the measurement precision. We find that by applying a suitable pulse after OAT, the resonant frequency can be inferred and the light shift can be reduced by using composite pulses. To increase the signal slope, we use anti-OAT dynamics to perform interaction-based readout after interrogation. By designing suitable composite pulses, it can significantly increase the signal response and further improve the measurement precision. Although both schemes can mitigate the light shift, it cannot be entirely eliminated. Thus, we develop the autobalanced entanglement-enhanced Ramsey spectroscopy. By using combination of different sequences with short and long interrogation times and feedback control, the light shift of both our protocols can be completely suppressed, which increases the measurement accuracy. Besides, we also investigate the effects of background atom-atom interaction and find that it only reduces the measurement precision without introducing additional frequency shift. Our study offers an alternative method for achieving precise frequency measurement, which has the potential to be of significant application in quantum sensors such as atomic clocks.

H. Z. Cummins

J. D. Koralek, Luyi Yang, D. R. Tibbetts +3 more

Phase-sensitive transient grating spectroscopy was used to measure the Doppler shift of light diffracted off moving spin and charge density waves, allowing complete characterization of spin and charge transport in the 2D Fermi gas.

Stephen Mark Barnett