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

arXiv:2007.05583 · Physical Review Applied

Quantum Advantage with Seeded Squeezed Light for Absorption Measurement

Fu Li, Tian Li, Marlan O. Scully, G. S. Agarwal

Published Apr 20, 2021• 33 citations
arXivHTMLPDF

Abstract

Absorption measurement is an exceptionally versatile tool for many applications in science and engineering. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the fundamental Poisson distribution of the photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use seeded squeezed light to demonstrate that direct-absorption measurements can be performed with a sensitivity beyond the shot-noise limit. We present a practically realizable scheme, where intensity-squeezed beams are generated by a seeded four-wave mixing process in an atomic rubidium-vapor cell. More than 1.2 dB quantum advantage for the measurement sensitivity is obtained at faint absorption levels ($\ensuremath{\le}10\mathrm{%}$). We also present a detailed theoretical analysis to show that the observed quantum advantage when corrected for optical loss would be equivalent to 3 dB. Our experiment demonstrates a direct sub-shot-noise measurement of absorption that requires neither homodyne or lock-in nor logic coincidence-detection schemes. It is therefore very applicable in many circumstances where sub-shot-noise-level absorption measurements are highly desirable.

DOI
10.1103/physrevapplied.15.044030

Related papers

Observation of Quantum Advantage with Squeezed Light for Absorption Measurement

Fu Li, Tian T. Li, Marlan O. Scully +1 more

Absorption measurements are routinely used in science and engineering, it is an exceptionally versatile tool for most applications. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the fundamental Poisson distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use bright squeezed light to demonstrate direct absorption measurement can be performed with sensitivity beyond the shot-noise limit. We present a practically realizable scheme, where the bright squeezed light is in the continuous-variable regime generated by the four-wave mixing process in an atomic rubidium vapor. This is a direct sub-shot-noise measurement of absorption, and more than 1 dB quantum advantage for the measurement sensitivity is demonstrated at faint absorption levels. A theoretical model that yields excellent agreements with experimental observations is also provided.

•Jul 10, 2020•1 citation

Quantum advantage of seeded, squeezed light in absorption and gain measurement

G. S. Agarwal

We use bright squeezed light to demonstrate that direct absorption and gain measurements can be performed with sensitivity beyond the shot-noise limit without requiring homodyne/lock-in, or logic coincidence detection schemes. Previously we reported more than 1 dB quantum advantage [ 3 dB when corrected losses in optical paths] for the measurement sensitivity at faint absorption levels. We present our detailed results on definite quantum advantage of about 3dB in measurements of Brillouin gain.

Optical and Quantum Sensing and Precision Metrology II•Mar 9, 2022•0 citations

Sub-shot-noise Rydberg EIT spectrum

Hongmei Yan, Mingyong Jing, Yanjie Tong +8 more

Abstract Atom-based sensing with optical readout is fundamentally limited by photon shot noise. Squeezed light can effectively suppress this noise of optical readout, thereby enabling measurement sensitivities beyond the standard quantum limit, but their application in light–atom hybrid systems is often hindered by absorption losses of atomic medium. Here, we demonstrate the first realization of electromagnetically induced transparency spectrum in a Rydberg-atom system using a squeezed probe field that surpasses the photon shot noise limit. Our theoretical model identifies atomic transit and absorption-induced losses as the primary factors limiting squeezing preservation. Experimentally, we engineer the atomic ensemble as a medium with tunable transmittance by employing Doppler-matched velocity-selective excitation to suppress absorption, achieving a squeezing transmission of 90.4 $$\%$$ % for -1.7 dB squeezed light through a cesium vapor cell. This work is a critical step towards quantum-enhanced Rydberg atom sensors.

PhotoniX•Dec 15, 2025•5 citations

Bright seeded and quasi-continuous two-mode intensity squeezing in commercial fiber

Elad Zehavi, Alon Bernstein, Michal Natan +4 more

Squeezed states of light enable optical measurements with sensitivity beyond the shot noise limit of detection with classical light. Optical fibers represent a major potential platform for quantum squeezed sensing due to the extremely low loss and perfect single-spatial-mode operation. In this work, we demonstrate two-mode intensity squeezing directly within a commercially available optical fiber, based on a four-wave mixing process. The setup operates in a quasi-continuous-wave mode using 15 ns long pulses and relies on standard laser diode sources, telecommunication electro-optic modulators, and simple photo-detectors. The process is seeded by a coherent signal input, generating bright squeezed output states. Absolute noise reduction by 4 dB below the classical shot-noise limit is detected directly with no post-processing, for output signal and idler pulses of 2.4 × 10 6 photons in average. The results are applicable to quantum interferometry over fiber using simple, readily available components.

Optics Express•Jul 9, 2026•0 citations

Absorption spectroscopy at the ultimate quantum limit from single-photon states

Rebecca Whittaker, Chris Erven, Alex Neville +4 more

Absorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in laser absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use wavelength-correlated and tuneable photon pairs to demonstrate how absorption spectroscopy can be performed with precision beyond the shot-noise limit and near the ultimate quantum limit by using the optimal probe for absorption measurement—single photons. We present a practically realisable scheme, which we characterise both the precision and accuracy of by measuring the response of a control feature. We demonstrate that the technique can successfully probe liquid samples and using two spectrally similar types of haemoglobin we show that obtaining a given precision in resolution requires fewer heralded single probe photons compared to using an idealised laser.

arXiv:1508.00849•New Journal of Physics•Dec 21, 2016•93 citations

Measurement of intensity difference squeezing via non-degenerate four-wave mixing process in an atomic vapor

X. D. Yu, Zengming Meng, Jing Zhang

We report the measurement of the intensity difference squeezing via the non-degenerate four-wave mixing process in a rubidium atomic vapor medium. Two pairs of balanced detection systems are employed to measure the probe and the conjugate beams, respectively. It is convenient to get the quantum shot noise limit, the squeezed and the amplified noise power spectra. We also investigate the influence of the input extra quadrature amplitude noise of the probe beam. The influence of the extra noise can be minimized and the squeezing can be optimized under the proper parameter condition. We measure the −3.7-dB intensity difference squeezing when the probe beam has a 3-dB extra quadrature amplitude noise. This result is slightly smaller than −4.1 dB when the ideal coherent light (no extra noise) for the probe beam is used.

Chinese Physics B•Sep 1, 2013•4 citations
Absorption measurement is an exceptionally versatile tool for many applications in science and engineering. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the fundamental Poisson distribution of the photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use seeded squeezed light to demonstrate that direct-absorption measurements can be performed with a sensitivity beyond the shot-noise limit. We present a practically realizable scheme, where intensity-squeezed beams are generated by a seeded four-wave mixing process in an atomic rubidium-vapor cell. More than 1.2 dB quantum advantage for the measurement sensitivity is obtained at faint absorption levels (\ensuremath{\le}10\mathrm{%}). We also present a detailed theoretical analysis to show that the observed quantum advantage when corrected for optical loss would be equivalent to 3 dB. Our experiment demonstrates a direct sub-shot-noise measurement of absorption that requires neither homodyne or lock-in nor logic coincidence-detection schemes. It is therefore very applicable in many circumstances where sub-shot-noise-level absorption measurements are highly desirable.
Absorption measurements are routinely used in science and engineering, it is an exceptionally versatile tool for most applications. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the fundamental Poisson distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use bright squeezed light to demonstrate direct absorption measurement can be performed with sensitivity beyond the shot-noise limit. We present a practically realizable scheme, where the bright squeezed light is in the continuous-variable regime generated by the four-wave mixing process in an atomic rubidium vapor. This is a direct sub-shot-noise measurement of absorption, and more than 1 dB quantum advantage for the measurement sensitivity is demonstrated at faint absorption levels. A theoretical model that yields excellent agreements with experimental observations is also provided.
Abstract Atom-based sensing with optical readout is fundamentally limited by photon shot noise. Squeezed light can effectively suppress this noise of optical readout, thereby enabling measurement sensitivities beyond the standard quantum limit, but their application in light–atom hybrid systems is often hindered by absorption losses of atomic medium. Here, we demonstrate the first realization of electromagnetically induced transparency spectrum in a Rydberg-atom system using a squeezed probe field that surpasses the photon shot noise limit. Our theoretical model identifies atomic transit and absorption-induced losses as the primary factors limiting squeezing preservation. Experimentally, we engineer the atomic ensemble as a medium with tunable transmittance by employing Doppler-matched velocity-selective excitation to suppress absorption, achieving a squeezing transmission of 90.4 %\%% % for -1.7 dB squeezed light through a cesium vapor cell. This work is a critical step towards quantum-enhanced Rydberg atom sensors.
Squeezed states of light enable optical measurements with sensitivity beyond the shot noise limit of detection with classical light. Optical fibers represent a major potential platform for quantum squeezed sensing due to the extremely low loss and perfect single-spatial-mode operation. In this work, we demonstrate two-mode intensity squeezing directly within a commercially available optical fiber, based on a four-wave mixing process. The setup operates in a quasi-continuous-wave mode using 15 ns long pulses and relies on standard laser diode sources, telecommunication electro-optic modulators, and simple photo-detectors. The process is seeded by a coherent signal input, generating bright squeezed output states. Absolute noise reduction by 4 dB below the classical shot-noise limit is detected directly with no post-processing, for output signal and idler pulses of 2.4 × 10 6 photons in average. The results are applicable to quantum interferometry over fiber using simple, readily available components.
Absorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in laser absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use wavelength-correlated and tuneable photon pairs to demonstrate how absorption spectroscopy can be performed with precision beyond the shot-noise limit and near the ultimate quantum limit by using the optimal probe for absorption measurement—single photons. We present a practically realisable scheme, which we characterise both the precision and accuracy of by measuring the response of a control feature. We demonstrate that the technique can successfully probe liquid samples and using two spectrally similar types of haemoglobin we show that obtaining a given precision in resolution requires fewer heralded single probe photons compared to using an idealised laser.
We report the measurement of the intensity difference squeezing via the non-degenerate four-wave mixing process in a rubidium atomic vapor medium. Two pairs of balanced detection systems are employed to measure the probe and the conjugate beams, respectively. It is convenient to get the quantum shot noise limit, the squeezed and the amplified noise power spectra. We also investigate the influence of the input extra quadrature amplitude noise of the probe beam. The influence of the extra noise can be minimized and the squeezing can be optimized under the proper parameter condition. We measure the −3.7-dB intensity difference squeezing when the probe beam has a 3-dB extra quadrature amplitude noise. This result is slightly smaller than −4.1 dB when the ideal coherent light (no extra noise) for the probe beam is used.