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arXiv:2505.03459

Methods for quantum interference in atomic ensemble

Niladri Ghorui, Sudip Mandal, Swarupananda Pradhan

Published May 6, 2025• 0 citations
arXivHTMLPDF

Abstract

An experimental method for obtaining quantum interference signal in atomic ensemble using a bi-chromatic field is discussed. Here, the quantum interference signal is obtained by scanning the magnetic field rather than conventional method of changing the frequency separation between the light fields. We could simultaneously observe resonances due to population redistribution and quantum superposition between non-degenerate states, which otherwise involves fundamentally different approaches. The method is implemented to Rubidium atoms in buffer gas filled as well as anti-relaxation coated atomic cells. Apart from phenomenological interest, the modified experimental procedure is found to be convenient for in-situ calibration of three axis magnetic coils. The investigation will be useful for high as well as low vector magnetic field sensing.

DOI
10.48550/arxiv.2505.03459

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An experimental method for obtaining quantum interference signal in atomic ensemble using a bi-chromatic field is discussed. Here, the quantum interference signal is obtained by scanning the magnetic field rather than conventional method of changing the frequency separation between the light fields. We could simultaneously observe resonances due to population redistribution and quantum superposition between non-degenerate states, which otherwise involves fundamentally different approaches. The method is implemented to Rubidium atoms in buffer gas filled as well as anti-relaxation coated atomic cells. Apart from phenomenological interest, the modified experimental procedure is found to be convenient for in-situ calibration of three axis magnetic coils. The investigation will be useful for high as well as low vector magnetic field sensing.
The atomic population trapped in uncoupled atomic states is a limiting factor for processes based on laser-atom interaction. The use of repump laser, bi-chromatic field, and vector magnetic field are explored in degenerate as well as non-degenerate atomic system to overcome the limitation. The magnetic resonance of 85Rb atoms under these complementary conditions are investigated in a buffer gas filled cell. The most suitable condition is achieved by the combined action of a bi-chromatic light with a specific combination of magnetic fields for non-degenerate levels where the relevant magnetic resonance shows more than 7-fold increase in its amplitude. The phenomenon is consistently observed through RF as well as magnetic field de-modulation technique. It will lead to similar improvement in the sensitivity of the atomic magnetometers. The optical pumping of the atomic population to the stretch state by manipulation of magnetic field will be of general interest involving quantum technology.
We have investigated some possibilities to use effect of Electromagnetically Induced Transparency (EIT), which is based on quantum interference, for measuring magnetic fields. Multi-frequency laser light is driving atomic transitions (e.g. in a Λ-type excitation scheme), and the atoms are decaying into a super positional dark state, in which the population is trapped, if the frequencies of the applied light fulfills certain conditions. Then the atomic medium becomes transparent for the exciting electromagnetic fields. The observed line width of this "transparency window" is not limited by the natural line width of the involved optical transitions and can be decreased down to a few hundredths of Hertz. As a consequence, this narrow feature can be used as a sensitive probe if the frequencies fulfill the required conditions, which are dependent on the energy positions of the involved atomic levels. These energy positions are influenced by external magnetic fields, thus the observation of EIT can be used to determine external magnetic fields strengths. In our approach a so called Hanle-configuration is used, where only one laser frequency is used to simultaneously excite σ+- and σ--transitions within a single hyperfine transition of the Rb87 Dl-line. In this configuration a resonant Λ-system is formed at zero magnetic field. The detuning from two-photon resonance is caused by a magnetic field scanned in laser propagation direction. Any additional probe magnetic field characteristically changes the width and shape of the EIT transparency window resonance; hence the probe magnetic field can be determined directly from the shape of this resonance.
The determination of electron spin polarization by controlling the atomic population distributions of ground states has been proposed. The polarization could be deduced by generating different population symmetries by polarized lights. The polarization of the atomic ensembles was decoded from optical depth in different transmissions of linearly and elliptic polarized lights. The feasibility of the method has been validated theoretically and experimentally. Moreover, the influences of relaxation and magnetic fields are analyzed. The transparency induced by high pump rates are investigated experimentally, and the influences of ellipticity of lights are also discussed. The in-situ polarization measurement was achieved without changing optical path of atomic magnetometer, which provides a new way to interrogate the performance of atomic magnetometer and in-situ monitoring the hyperpolarization of nuclear spins for atomic co-magnetometer.
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Precise control of magnetic fields is a frequent challenge encountered in experiments with atomic quantum gases. Here we present a simple method for performing in situ monitoring of magnetic fields that can readily be implemented in any quantum-gas apparatus in which a dedicated field-stabilization approach is not feasible. The method, which works by sampling several Rabi resonances between magnetically field sensitive internal states that are not otherwise used in a given experiment, can be integrated with standard measurement sequences at arbitrary fields. For a condensate of 87Rb atoms, we demonstrate the reconstruction of Gauss-level bias fields with an accuracy of tens of microgauss and with millisecond time resolution. We test the performance of the method using measurements of slow resonant Rabi oscillations on a magnetic-field sensitive transition and give an example for its use in experiments with state-selective optical potentials.
Abstract We present experimental and theoretical investigations of the dependence of double Hanle resonance spectrum on the light polarization angle and the direction of the applied transverse magnetic field (TMF). The experiments are done for F g = 2 → F e = 1 transition of 87Rb D1 line using a rubidium vapor cell containing buffer gas. We show that a small light polarization component along the direction of TMF introduces asymmetry in the double Hanle resonance signal. Both the magnitude and sign of asymmetry in the signal are sensitive to the TMF orientation, suggesting a possible method for in-situ measurement of the direction of the magnetic fields generated by the coils. The physical origin of this asymmetry is explained by considering the redistribution of population among the ground-state Zeeman sublevels in the presence of TMF. In addition, we systematically vary both the polarization angle and TMF direction to study their effect on the line profile of Hanle resonances. We demonstrate that a double Hanle resonance changes to a dark Hanle resonance by rotating the light polarization vector irrespective of the TMF direction. We have developed a simple theoretical model based on a degenerate two-level system to explain our experimental observations.