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Observation of spin echoes of laser-cooled Rb atoms

義朗 高橋, Yoshiro Takahashi, 和仁 本多, Kazuhito Honda, 剛 桑本, T. Kuwamoto, 健二 豊田, Kenji Toyoda, 努 藪崎, T. Yabuzaki

Published May 1, 1999• 0 citations
OpenAlex

Abstract

We have observed gradient spin echoes in the ground state of laser-cooled 85Rb atoms through paramagnetic Faraday rotation. We have obtained the exact expression for the behavior of the echo signal under the assumption that the motion of the cold atoms is ballistic. The qualitative behaviors predicted by the theory have been confirmed experimentally. We demonstrate the usefulness of the spin echo method for the diagnosis for the atomic density distribution of cold atoms. We discuss various advantages of the spin echo as a novel method for temperature measurement.

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Observation of spin echoes of laser-cooled Rb atoms

Yoshiro Takahashi, Takayuki Shimizu, N. Tanaka +3 more

We have observed gradient spin echoes in the ground state of $\mathrm{l}\mathrm{a}\mathrm{s}\mathrm{e}\mathrm{r}\ensuremath{-}\mathrm{c}\mathrm{o}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{d}{}^{85}\mathrm{Rb}$ atoms through paramagnetic Faraday rotation. We have obtained the exact expression for the behavior of the echo signal under the assumption that the motion of the cold atoms is ballistic. The qualitative behaviors predicted by the theory have been confirmed experimentally. We demonstrate the usefulness of the spin echo method for the diagnosis for the atomic density distribution of cold atoms. We discuss various advantages of the spin echo as a novel method for temperature measurement.

Physical Review A•May 1, 1999•4 citations

Observation of Larmor spin precession of laser-cooled Rb atoms via paramagnetic Faraday rotation

T. Isayama, Yoshiro Takahashi, N. Tanaka +3 more

We have observed Larmor spin precession in the ground state of laser-cooled ${}^{85}\mathrm{Rb}$ atoms through paramagnetic Faraday rotation. We have been able to obtain a precision of $18\mathrm{pT}$ in the determination of the applied magnetic field, which proves the usefulness of laser-cooled atoms as an atomic magnetometer.

Physical Review A•Jun 1, 1999•37 citations

Detection of spin coherence in cold atoms via Faraday rotation fluctuations

Maheswar Swar, Dibyendu Roy, Subhajit Bhar +2 more

We report noninvasive detection of spin coherence in a collection of Raman-driven cold atoms using dispersive Faraday rotation fluctuation measurements, which opens possibilities of probing spin correlations in quantum gases and other similar systems. We demonstrate five orders of magnitude enhancement of the measured signal strength as compared to traditional spin noise spectroscopy with thermal atoms in equilibrium. Our observations are in good agreement with the comprehensive theoretical modeling of the driven atoms at various temperatures. The extracted spin relaxation rate of cold rubidium atoms with atom number density $\ensuremath{\sim}10{\phantom{\rule{0.16em}{0ex}}}^{9}/{\mathrm{cm}}^{3}$ is of the order of $3\phantom{\rule{0.16em}{0ex}}\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0.16em}{0ex}}10{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ at 150 $\ensuremath{\mu}\mathrm{K}$, two orders of magnitude less than $3\phantom{\rule{0.16em}{0ex}}\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0.16em}{0ex}}10{\phantom{\rule{0.16em}{0ex}}}^{5}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ of that of a thermal atomic vapor with atom number density $\ensuremath{\sim}10{\phantom{\rule{0.16em}{0ex}}}^{12}/{\mathrm{cm}}^{3}$ at 373 K.

arXiv:2104.10473•Physical Review Research•Dec 10, 2021•19 citations

Faraday rotation echo spectroscopy and detection of quantum fluctuations

Shao-Wen Chen, Ren-Bao Liu

Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials.

arXiv:1403.0420•Scientific Reports•Apr 15, 2014•18 citations

Continuous Optical Measurement of Cold Atomic Spins

Gregory A. Smith

Quantum measurement is one of the most important features of quantum theory. Although mathematical predictions have been verified in great detail, practical implementation has lagged behind. Only recently have people begun to take advantage of quantum measurement properties to produce new technologies. This research helps fill that technological gap by experimental examination of a continuous, optical measurement for an ensemble of cold atomic spins. The essential physics reduces to the interaction between an atomic ensemble and a weak optical field, which has many well known results. While this work demonstrates many novel applications of the interaction, it also shows that the whole can be more than the sum of the individual parts. Starting with basic characterization of the measurement system using laser-cooled cæsium atoms, the mean value of a spin component is obtained in real time. In essence, the angular momentum of the atomic spins creates a Faraday-like rotation in the polarization of a laser probe beam. With slight modifications, additional spin components are also observed, and are shown to be in good agreement with predictions. In measuring spin dynamics, it is important to account for effects of the probe on the spin states as well. Capitalizing on this as a resource, the probe-induced ac-Stark shift is used to transform a quasi-classical spin-coherent state into a highly quantum Schrödinger cat type of superposition between two spin states. Finally, this work combines all the previous results to demonstrate how a continuous measurement of the spin with a carefully crafted evolution created in part by the probe, allows for nearly real-time determination of the complete spin density matrix. In a single 1.5 millisecond run, a spin density matrix is determined with fidelities ranging from about 85% to 90% across a wide spectrum of test states.

•Jan 1, 2006•0 citations

Observation of Faraday Rotation in Cold Atoms in an Integrating Sphere

Ben-Chang Zheng, Hua-Dong Cheng, Yan-Ling Meng +3 more

The Faraday rotation of weak linearly polarized probe light is observed as it passes through a sample of cold 87 Rb atoms prepared by diffused light in an integrating sphere. The rotation angle of the probe light-polarization as functions of laser intensity, detuning and biased magnetic field is measured. A Ramsey fringe with a linewidth of 35 Hz and contrast up to 92% is demonstrated. This method has potential applications in improving the performance of atomic clocks with cold atoms.

Chinese Physics Letters•Jul 1, 2014•1 citation
We have observed gradient spin echoes in the ground state of laser-cooled 85Rb atoms through paramagnetic Faraday rotation. We have obtained the exact expression for the behavior of the echo signal under the assumption that the motion of the cold atoms is ballistic. The qualitative behaviors predicted by the theory have been confirmed experimentally. We demonstrate the usefulness of the spin echo method for the diagnosis for the atomic density distribution of cold atoms. We discuss various advantages of the spin echo as a novel method for temperature measurement.
We have observed gradient spin echoes in the ground state of $\mathrm{l}\mathrm{a}\mathrm{s}\mathrm{e}\mathrm{r}\ensuremath{-}\mathrm{c}\mathrm{o}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{d}{}^{85}\mathrm{Rb}$ atoms through paramagnetic Faraday rotation. We have obtained the exact expression for the behavior of the echo signal under the assumption that the motion of the cold atoms is ballistic. The qualitative behaviors predicted by the theory have been confirmed experimentally. We demonstrate the usefulness of the spin echo method for the diagnosis for the atomic density distribution of cold atoms. We discuss various advantages of the spin echo as a novel method for temperature measurement.
We have observed Larmor spin precession in the ground state of laser-cooled 85Rb{}^{85}\mathrm{Rb}85Rb atoms through paramagnetic Faraday rotation. We have been able to obtain a precision of 18pT18\mathrm{pT}18pT in the determination of the applied magnetic field, which proves the usefulness of laser-cooled atoms as an atomic magnetometer.
We report noninvasive detection of spin coherence in a collection of Raman-driven cold atoms using dispersive Faraday rotation fluctuation measurements, which opens possibilities of probing spin correlations in quantum gases and other similar systems. We demonstrate five orders of magnitude enhancement of the measured signal strength as compared to traditional spin noise spectroscopy with thermal atoms in equilibrium. Our observations are in good agreement with the comprehensive theoretical modeling of the driven atoms at various temperatures. The extracted spin relaxation rate of cold rubidium atoms with atom number density $\ensuremath{\sim}10{\phantom{\rule{0.16em}{0ex}}}^{9}/{\mathrm{cm}}^{3}$ is of the order of $3\phantom{\rule{0.16em}{0ex}}\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0.16em}{0ex}}10{\phantom{\rule{0.16em}{0ex}}}^{3}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ at 150 $\ensuremath{\mu}\mathrm{K}$, two orders of magnitude less than $3\phantom{\rule{0.16em}{0ex}}\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0.16em}{0ex}}10{\phantom{\rule{0.16em}{0ex}}}^{5}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ of that of a thermal atomic vapor with atom number density $\ensuremath{\sim}10{\phantom{\rule{0.16em}{0ex}}}^{12}/{\mathrm{cm}}^{3}$ at 373 K.
Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials.
Quantum measurement is one of the most important features of quantum theory. Although mathematical predictions have been verified in great detail, practical implementation has lagged behind. Only recently have people begun to take advantage of quantum measurement properties to produce new technologies. This research helps fill that technological gap by experimental examination of a continuous, optical measurement for an ensemble of cold atomic spins. The essential physics reduces to the interaction between an atomic ensemble and a weak optical field, which has many well known results. While this work demonstrates many novel applications of the interaction, it also shows that the whole can be more than the sum of the individual parts. Starting with basic characterization of the measurement system using laser-cooled cæsium atoms, the mean value of a spin component is obtained in real time. In essence, the angular momentum of the atomic spins creates a Faraday-like rotation in the polarization of a laser probe beam. With slight modifications, additional spin components are also observed, and are shown to be in good agreement with predictions. In measuring spin dynamics, it is important to account for effects of the probe on the spin states as well. Capitalizing on this as a resource, the probe-induced ac-Stark shift is used to transform a quasi-classical spin-coherent state into a highly quantum Schrödinger cat type of superposition between two spin states. Finally, this work combines all the previous results to demonstrate how a continuous measurement of the spin with a carefully crafted evolution created in part by the probe, allows for nearly real-time determination of the complete spin density matrix. In a single 1.5 millisecond run, a spin density matrix is determined with fidelities ranging from about 85% to 90% across a wide spectrum of test states.