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arXiv:2302.12660 · Optics Continuum

Optimizing population accumulation in a designated single Zeeman state using microwave spectroscopy

Jia-You Liou, Chien‐Ting Wu, Hsuan-Jui Su, Yi‐Hsin Chen

Published Aug 28, 2023• 3 citations
arXivHTMLPDF

Abstract

We present an all-optical method for the highly efficient preparation of cold atoms in a specific Zeeman state, such as the magnetically insensitive clock state ( m F = 0) or a particular state suitable for quantum information processing and storage. This technique employs a single microwave spectrum, enabling precise determination of the population distribution, microwave polarization ratio, and microwave Rabi frequency individually. By analyzing the microwave spectrum, we can track the population distribution while systematically varying the power or period of the optical pumping field(s). In steady-state conditions, our simplified model, which incorporates resonant and off-resonant transitions, reveals an upper limit to the population purity. Through the optimization of the intensity and polarization of the optical pumping field, we have achieved exceptional population purities of up to 96(2)% or 98(1)% for the desired quantum state. These remarkable results indicate a significant advancement in state preparation accuracy. Our all-optical method introduces an approach to achieving high-purity atomic states while employing novel microwave spectroscopy to accurately detect all unknown parameters, offering valuable insights and potential applications in precision measurement and quantum computation research.

DOI
10.1364/optcon.498692

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We present an all-optical method for the highly efficient preparation of cold atoms in a specific Zeeman state, such as the magnetically insensitive clock state ( m F = 0) or a particular state suitable for quantum information processing and storage. This technique employs a single microwave spectrum, enabling precise determination of the population distribution, microwave polarization ratio, and microwave Rabi frequency individually. By analyzing the microwave spectrum, we can track the population distribution while systematically varying the power or period of the optical pumping field(s). In steady-state conditions, our simplified model, which incorporates resonant and off-resonant transitions, reveals an upper limit to the population purity. Through the optimization of the intensity and polarization of the optical pumping field, we have achieved exceptional population purities of up to 96(2)% or 98(1)% for the desired quantum state. These remarkable results indicate a significant advancement in state preparation accuracy. Our all-optical method introduces an approach to achieving high-purity atomic states while employing novel microwave spectroscopy to accurately detect all unknown parameters, offering valuable insights and potential applications in precision measurement and quantum computation research.
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We demonstrate a simple, all-optical technique to prepare and determine the desired internal quantum states in multi-Zeeman-sublevel atoms. By choosing appropriate coupling and pumping laser beams, atoms can be easily prepared in a desired Zeeman sublevel with high purity or in any chosen ground-state population distributions (spin-polarized quantum-state engineering). The population distributions or state purities of such prepared atomic states can be determined by using a weak, circularly polarized probe beam due to differences in transition strengths among different Zeeman sublevels. This technique will have potential impact on quantum-information processing in multilevel atomic systems.
We present a demonstration of a cold-atom optical-microwave double resonance (DR) Ramsey clock utilising an additively manufactured loop-gap-resonator cavity and grating magneto-optical trap (GMOT). The use of additive manufacturing allows for complex cavity structures, more difficult to produce with traditional machining techniques, while the GMOT architecture significantly simplifies the optical system required to trap and cool the atomic sample. In the current demonstration a single laser is used to trap < 3 × 106 87Rb atoms, cool them to below 10 µK, optically pump and read-out state populations of the atoms after microwave interrogation. A Ramsey-type interrogation scheme is employed with an empirically evaluated optimum free evolution time of 10 ms, limited by the loss of signal due to atoms falling out of the read-out beam. We demonstrate a short-term stability of < 2×10−11τ−1/2, in reasonable agreement with the predicted short-term stability based on the signal to noise ratio of the measured Ramsey fringes. Excellent field homogeneity of the cavity microwave field is demonstrated though Rabi oscillations, while almost complete optical pumping and good field orientation is evidenced by Zeeman spectroscopy of the ground-state hyperfine energy levels. This work is a novel approach towards more compact and portable cold-atom microwave clocks with significant potential for further miniaturization of the system.
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An optical pumping scheme is presented that uses incoherent Raman transitions to prepare a trapped cesium atom in a specific Zeeman state within the 6S1/26{S}_{1/2}6S1/2​, F=3F=3F=3 hyperfine manifold. An important advantage of this scheme over existing optical pumping schemes is that the atom can be prepared in any of the F=3F=3F=3 Zeeman states. We describe an experimental implementation of the scheme and show that a fraction $0.57\ifmmode\pm\else\textpm\fi{}0.02$ of the total population can be prepared in the desired state, with the remaining population distributed fairly uniformly among the six other states. We demonstrate the scheme in the context of cavity quantum electrodynamics, but the technique is equally applicable to a wide variety of atomic systems with hyperfine ground-state structure.
We present the results of stroboscopic microwave spectroscopy of a radio-frequency-dressed optically pumped magnetometer. The interaction between radio-frequency-dressed atoms and a synchronously pulsed microwave field followed by Voigt-effect-based optical probing allows us to perform a proper ground-state interrogation for dressed state and assess the efficiency of the state preparation process. This work shows that through the stroboscopic technique the microwave spectrum is simplified when compared to the continuous counterpart. This is a necessary step towards investigating vector magnetometers in unshielded environments, where the influence of the nonlinear Zeeman effect, a source of heading errors, would otherwise be spectrally unresolved in dressed states. To theoretically describe the system, we solve the dynamical equation of the density matrix employing Floquet expansion. Our theoretical results are in good agreement with experimental measurements over a wide range of parameters and pumping conditions.