Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Conference on Lasers and Electro-Optics

Ultra-Sensitive Faraday Rotation Measurements from an Atom-Light Quantum Interface

Marco Koschorreck, M. Napolitano, B. Dubost, Morgan W. Mitchell

Published Jan 1, 2009• 0 citations
Publisher

Abstract

Highly sensitive Faraday rotation measurements are performed on an ensemble of 87Rb. The deduced interaction strength is discussed in the context of spin squeezing. We present a method for spin state tomography based on Faraday rotation measurements.
DOI
10.1364/iqec.2009.iwg3

Related papers

Ultra-sensitive Faraday rotation measurements from an atom-light quantum interface

Marco Koschorreck, M. Napolitano, B. Dubost +2 more

Atomic ensembles have gained a lot of interest in the last decade for their prospective use as quantum memories, in precision measurements and other applications in quantum information processing. The atomic part of the interface presented here is an all-optically trapped atomic ensemble of 87Rb at a temperature of 25 muK. The ensemble consists of 106atoms and has an elongated shape with an aspect ratio of about 250:1. The resonant optical depth is around 50. The light part is an off-resonant polarized laser beam which dispersively probes the atomic state. The detection is a shot-noise limited polarization measurement of light pulses of a few mus and 3 x 105photons.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•0 citations

Simultaneous observation of super-Heisenberg scaling and spin squeezing in a nonlinear measurement of atomic spins

R. J. Sewell, M. Napolitano, N. Behbood +3 more

Techniques for making quantum-limited nonlinear measurements have attracted a great deal of recent attention because they allow a measurement sensitivity that improves as the number of measuring particles (e.g. photons) increases faster than an equivalent linear measurement. This super-Heisenberg scaling was recently demonstrated in a proof-of-principle experiment [1], in which a measurement Hamiltonian of the form studied in Ref. [2] was carefully engineered by exploiting nonlinearities in a Faraday rotation based measurement of atomic spins. However, despite the improved scaling, the absolute measurement sensitivity in this experiment remained significantly worse than a linear Faraday rotation measurement due to the weak atom-light coupling strength of the nonlinear Faraday rotation, and effect of higher-order nonlinearities at large photon number. This leaves open the question of whether it is possible to make a nonlinear measurement that both benefits from the improved scaling, and competes in absolute sensitivity with linear techniques.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•May 1, 2013•0 citations

Squeezed-Light Optical Magnetometry

Florian Wolfgramm, Alessandro Ceré, Federica A. Beduini +3 more

We demonstrate a light-shot-noise-limited magnetometer based on the Faraday effect in a hot unpolarized ensemble of rubidium atoms. By using off-resonant, polarization-squeezed probe light, we improve the sensitivity of the magnetometer by 3.2 dB. The technique could improve the sensitivity of the most advanced magnetometers and quantum nondemolition measurements of atomic spin ensembles.

arXiv:1008.1721•Physical Review Letters•Jul 29, 2010•240 citations

Entanglement-enhanced probing of a delicate material system

Florian Wolfgramm, Chiara Vitelli, Federica A. Beduini +2 more

Probing of delicate systems demands high sensitivity from limited probe energy. Quantum optical techniques to beat the standard quantum limit (SQL) offer a practical advantage for these measurements. Here we report the first entanglement-enhanced measurement of a delicate material system [1]. We non-destructively probe an atomic spin ensemble by near-resonant Faraday rotation, a measurement that is limited by probe-induced scattering in quantum memory and spin-squeezing applications [2]. We use narrowband, atom-resonant NooN states to beat the standard quantum limit of sensitivity, both on a per-photon and a per-damage basis.

•Jan 1, 2013•0 citations

Generation of spin squeezing in an ensemble of cold rubidium 87

Marco Koschorreck

At the beginning of the 20th century measurement precision was related exclusively to the capabilities of the experimenter and the apparatus. Any imprecision was attributed to imperfect devices for the measurement. Later on, when the quantumness of objects like photons, electrons, or atoms, was recognized, it became clear that the measurement and the object to be measured could no longer be separated. Both follow the laws of quantum physics which impose limits on the accuracy of any measurement. In the last three decades, a lot of research has been dedicated to find strategies to overcome these limitations. This new field of quantum metrology is where this work is placed. This thesis describes the generation of interparticle entanglement in form of a squeezed spin state in a cloud of cold 87Rb atoms by performing nondestructive spin measurements. Towards this goal, we have implemented a shot-noise limited polarization probing and detection system, atom counting by means of absorption imaging, spin state preparation via optical pumping and nondestructive spin state detection. The quantum noise limited spin readout with polarized light is characterized in two complementary ways in terms of sensitivity and all possible quantum and classical noise sources are measured. To address the rich opportunities provided in the multilevel structure of 87Rb with dispersive probing, we have developed and implemented a frequency offsetlock which allows a large tuning range of several GHz for the dispersive probing. Working with a magnetically sensitive atomic system triggered the development of a magnetic field imaging technique. This applies the elongated atomic sample and internal atomic states as a way of measuring magnetic fields over several millimeters with micrometer resolution and sensitivities down to a few tens of pT/ Hz. We developed a new method for tomographic measurements of the atomic density matrix. Based on our ability of shot noise limited detection of polarization rotations we can in principle, characterize the whole atomic spin state. First, measurements are shown and possible improvements are discussed. An in depth characterization of the light-atom interaction between polarized pulses of light and collective atomic states are the basis for measurements at the quantum level. On one side, we apply classical measurements of spin polarized atoms to measure the strength of the lightatom interaction. On the other side, we use quantum measurements of unpolarized atomic states to characterize all noise sources both technical and quantum. One of the major results of this thesis is the realization of quantum nondemolition measurements in a largespin system. We realized limitations to the performance of the QND measurement implied by higher order light shifts in multilevel atoms, which are often neglected for these kind of systems. We develop a technique which suppresses the detrimental effects of higher order light shifts and recovers an ideal QND measurement. The thesis culminates in the demonstration of spin squeezing in the magnetically sensitive ground state of 87Rb. We achieve a quantum noise reduction by 3 dB, where metrological sensitivity is improved by 2 dB beyond the standard quantum limit of a coherent spin state with the same spin polarization. We address the question how spatial and temporal inhomogeneities both in light and atoms influence the preparation of nonclassical states. An existing covariance matrix approach is extended and we apply it to study effects of detector time resolution, spatial inhomogeneities and atomic motion.

•Jan 1, 2011•11 citations

Quantum-Enhanced Measurements of Atomic Spin

Ana Predojević, Marco Koschorreck, M. Napolitano +6 more

We use narrow-band quantum light sources, tuned to the rubidium D1 resonance, to produce polarization-squeezed and polarization-NooN states for Heisenberg-limited measurements on atoms. By paramagnetic Faraday rotation these states measure the atomic spin polarization.

Conference on Lasers and Electro-Optics•Jan 1, 2009•1 citation
Atomic ensembles have gained a lot of interest in the last decade for their prospective use as quantum memories, in precision measurements and other applications in quantum information processing. The atomic part of the interface presented here is an all-optically trapped atomic ensemble of 87Rb at a temperature of 25 muK. The ensemble consists of 106atoms and has an elongated shape with an aspect ratio of about 250:1. The resonant optical depth is around 50. The light part is an off-resonant polarized laser beam which dispersively probes the atomic state. The detection is a shot-noise limited polarization measurement of light pulses of a few mus and 3 x 105photons.
Techniques for making quantum-limited nonlinear measurements have attracted a great deal of recent attention because they allow a measurement sensitivity that improves as the number of measuring particles (e.g. photons) increases faster than an equivalent linear measurement. This super-Heisenberg scaling was recently demonstrated in a proof-of-principle experiment [1], in which a measurement Hamiltonian of the form studied in Ref. [2] was carefully engineered by exploiting nonlinearities in a Faraday rotation based measurement of atomic spins. However, despite the improved scaling, the absolute measurement sensitivity in this experiment remained significantly worse than a linear Faraday rotation measurement due to the weak atom-light coupling strength of the nonlinear Faraday rotation, and effect of higher-order nonlinearities at large photon number. This leaves open the question of whether it is possible to make a nonlinear measurement that both benefits from the improved scaling, and competes in absolute sensitivity with linear techniques.
Probing of delicate systems demands high sensitivity from limited probe energy. Quantum optical techniques to beat the standard quantum limit (SQL) offer a practical advantage for these measurements. Here we report the first entanglement-enhanced measurement of a delicate material system [1]. We non-destructively probe an atomic spin ensemble by near-resonant Faraday rotation, a measurement that is limited by probe-induced scattering in quantum memory and spin-squeezing applications [2]. We use narrowband, atom-resonant NooN states to beat the standard quantum limit of sensitivity, both on a per-photon and a per-damage basis.
At the beginning of the 20th century measurement precision was related exclusively to the capabilities of the experimenter and the apparatus. Any imprecision was attributed to imperfect devices for the measurement. Later on, when the quantumness of objects like photons, electrons, or atoms, was recognized, it became clear that the measurement and the object to be measured could no longer be separated. Both follow the laws of quantum physics which impose limits on the accuracy of any measurement. In the last three decades, a lot of research has been dedicated to find strategies to overcome these limitations. This new field of quantum metrology is where this work is placed. This thesis describes the generation of interparticle entanglement in form of a squeezed spin state in a cloud of cold 87Rb atoms by performing nondestructive spin measurements. Towards this goal, we have implemented a shot-noise limited polarization probing and detection system, atom counting by means of absorption imaging, spin state preparation via optical pumping and nondestructive spin state detection. The quantum noise limited spin readout with polarized light is characterized in two complementary ways in terms of sensitivity and all possible quantum and classical noise sources are measured. To address the rich opportunities provided in the multilevel structure of 87Rb with dispersive probing, we have developed and implemented a frequency offsetlock which allows a large tuning range of several GHz for the dispersive probing. Working with a magnetically sensitive atomic system triggered the development of a magnetic field imaging technique. This applies the elongated atomic sample and internal atomic states as a way of measuring magnetic fields over several millimeters with micrometer resolution and sensitivities down to a few tens of pT/ Hz. We developed a new method for tomographic measurements of the atomic density matrix. Based on our ability of shot noise limited detection of polarization rotations we can in principle, characterize the whole atomic spin state. First, measurements are shown and possible improvements are discussed. An in depth characterization of the light-atom interaction between polarized pulses of light and collective atomic states are the basis for measurements at the quantum level. On one side, we apply classical measurements of spin polarized atoms to measure the strength of the lightatom interaction. On the other side, we use quantum measurements of unpolarized atomic states to characterize all noise sources both technical and quantum. One of the major results of this thesis is the realization of quantum nondemolition measurements in a largespin system. We realized limitations to the performance of the QND measurement implied by higher order light shifts in multilevel atoms, which are often neglected for these kind of systems. We develop a technique which suppresses the detrimental effects of higher order light shifts and recovers an ideal QND measurement. The thesis culminates in the demonstration of spin squeezing in the magnetically sensitive ground state of 87Rb. We achieve a quantum noise reduction by 3 dB, where metrological sensitivity is improved by 2 dB beyond the standard quantum limit of a coherent spin state with the same spin polarization. We address the question how spatial and temporal inhomogeneities both in light and atoms influence the preparation of nonclassical states. An existing covariance matrix approach is extended and we apply it to study effects of detector time resolution, spatial inhomogeneities and atomic motion.