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:2408.13817 · Physical Review Letters

Quantum-Enhanced Weak Absorption Estimation with Correlated Photons

Zhucheng Zhang, Xue Zhang, Jing Liu, Hui Yue Dong

Published Apr 4, 2025• 11 citations
arXivHTMLPDF

Abstract

Conventional absorption spectroscopy relies on coherent laser sources, and in turn suffers from the inherent limitation of shot noise, especially in estimating weak absorption. Here, we propose a measurement strategy with correlated photons to determine the weak absorption by distinguishing the output with and without photons, dubbed as the on-off measurement. We demonstrate that absorption spectroscopy that incorporates quantum correlations is capable of estimating weak absorption down to a single-photon level, even in noisy environments, achieving a precision comparable to that obtained through 1000 photons in conventional absorption spectroscopy. Our strategy provides a new method to probe fragile systems with weak absorption, avoiding the occurrence of light-induced damage.

DOI
10.1103/physrevlett.134.133604

Related papers

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

Enhanced absorption microscopy with correlated photon pairs

Ming Li, Chang‐Ling Zou, Di Liu +3 more

By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are fragile in noisy environments which leads to difficulties in revealing the quantum advantage. In this paper, we propose a scheme to improve optical absorption estimation precision by using the correlated photon pairs from spontaneous parametric down-conversion as the illumination. This scheme performs better than classical illumination when the loss is below a critical value. Experimentally, the scheme is demonstrated by a scanning transmission-type microscope that uses correlated photon illumination. As a result, the signal-to-noise ratio of a two-photon image shows a 1.36-fold enhancement over that of the single-photon image for single-layer graphene with a 0.98 transmittance. This enhancement factor will be larger when using a multimode squeezed state as the illumination.

arXiv:1807.01454•Physical Review A•Jul 18, 2018•17 citations

Quantum Enhanced Optical Measurements: From Ultra-High Sensitivity in Absorption Measurements to Ghost Microscopy

Elena Losero, Ivano Ruo Berchera, Alessio Avella +2 more

Quantum enhanced optical measurement protocols aim at reducing the uncertainty in the estimation of some physical quantities of a system below the shot-noise limit, classically unavoidable. In particular when small number of photons is used the shot noise can be the main source of uncertainty, in these cases the use of quantum light is of great interest. Note that there are several situations where the number of photons in the probe can not be increased arbitrarily, as when fragile biological samples are under investigation. Two different imaging protocols are discussed in the following.

Italian Quantum Information Science Conference (IQIS)•Jul 25, 2019•0 citations

Ultrasensitive Concentration and Chirality Measurements Realized by Sub-Shot-Noise Absorption Spectroscopy Using Entangled Photon Pairs

Korenobu Matsuzaki, Tahei Tahara

Quantum light, such as entangled photon pairs, is a special state of light that cannot be described by classical electrodynamics. Owing to its exotic nonclassical properties, the use of quantum light can open up a new possibility for spectroscopy that cannot be realized by a classical light source. Recently, using entangled photon pairs as the light source, we demonstrated ultrasensitive absorption spectroscopy with quantum-enhanced sensitivity [1]. This novel approach allows us to obtain absorption spectra with a noise level suppressed below the shot-noise limit, which is a fundamental and unavoidable limit in conventional absorption spectroscopy. In this presentation, we will discuss two applications of this sub-shot-noise absorption spectroscopy.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 26, 2023•0 citations

Demonstrating an absolute quantum advantage in direct absorption measurement

Paul‐Antoine Moreau, Javier Sabines-Chesterking, Rebecca Whittaker +5 more

Engineering apparatus that harness quantum theory promises to offer practical advantages over current technology. A fundamentally more powerful prospect is that such quantum technologies could out-perform any future iteration of their classical counterparts, no matter how well the attributes of those classical strategies can be improved. Here, for optical direct absorption measurement, we experimentally demonstrate such an instance of an absolute advantage per photon probe that is exposed to the absorbative sample. We use correlated intensity measurements of spontaneous parametric downconversion using a commercially available air-cooled CCD, a new estimator for data analysis and a high heralding efficiency photon-pair source. We show this enables improvement in the precision of measurement, per photon probe, beyond what is achievable with an ideal coherent state (a perfect laser) detected with 100% efficient and noiseless detection. We see this absolute improvement for up to 50% absorption, with a maximum observed factor of improvement of 1.46. This equates to around 32% reduction in the total number of photons traversing an optical sample, compared to any future direct optical absorption measurement using classical light.

arXiv:1611.07871•Scientific Reports•Jul 18, 2017•85 citations

Single-photon-added coherent state-based postselected weak measurement

Yi-Fang Ren, Yusuf Turek

We investigated precision measurements in a two-level system coupled to a single-photon-added coherent state (SPACS) under postselected weak measurement. We analyzed strategies for improving measurement precision, including parameter estimation and the signal-to-noise ratio (SNR) in postselected weak measurements, using the photon statistics of SPACS as the meter. Our results demonstrate that SPACS-based postselected weak measurements can outperform conventional measurement schemes in terms of precision. Additionally, we explicitly introduced an alternative weak measurement method, which is commonly applied in dispersive light-atom interactions. Our work presents a novel approach to addressing fundamental issues in quantum precision measurement based on photon statistics, and it provides a method for extracting the photon and phase shifts of radiation fields through the weak values of system observables.

Results in Physics•Jul 30, 2025•1 citation
Conventional absorption spectroscopy relies on coherent laser sources, and in turn suffers from the inherent limitation of shot noise, especially in estimating weak absorption. Here, we propose a measurement strategy with correlated photons to determine the weak absorption by distinguishing the output with and without photons, dubbed as the on-off measurement. We demonstrate that absorption spectroscopy that incorporates quantum correlations is capable of estimating weak absorption down to a single-photon level, even in noisy environments, achieving a precision comparable to that obtained through 1000 photons in conventional absorption spectroscopy. Our strategy provides a new method to probe fragile systems with weak absorption, avoiding the occurrence of light-induced damage.
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.
By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are fragile in noisy environments which leads to difficulties in revealing the quantum advantage. In this paper, we propose a scheme to improve optical absorption estimation precision by using the correlated photon pairs from spontaneous parametric down-conversion as the illumination. This scheme performs better than classical illumination when the loss is below a critical value. Experimentally, the scheme is demonstrated by a scanning transmission-type microscope that uses correlated photon illumination. As a result, the signal-to-noise ratio of a two-photon image shows a 1.36-fold enhancement over that of the single-photon image for single-layer graphene with a 0.98 transmittance. This enhancement factor will be larger when using a multimode squeezed state as the illumination.
Quantum enhanced optical measurement protocols aim at reducing the uncertainty in the estimation of some physical quantities of a system below the shot-noise limit, classically unavoidable. In particular when small number of photons is used the shot noise can be the main source of uncertainty, in these cases the use of quantum light is of great interest. Note that there are several situations where the number of photons in the probe can not be increased arbitrarily, as when fragile biological samples are under investigation. Two different imaging protocols are discussed in the following.
Quantum light, such as entangled photon pairs, is a special state of light that cannot be described by classical electrodynamics. Owing to its exotic nonclassical properties, the use of quantum light can open up a new possibility for spectroscopy that cannot be realized by a classical light source. Recently, using entangled photon pairs as the light source, we demonstrated ultrasensitive absorption spectroscopy with quantum-enhanced sensitivity [1]. This novel approach allows us to obtain absorption spectra with a noise level suppressed below the shot-noise limit, which is a fundamental and unavoidable limit in conventional absorption spectroscopy. In this presentation, we will discuss two applications of this sub-shot-noise absorption spectroscopy.
Engineering apparatus that harness quantum theory promises to offer practical advantages over current technology. A fundamentally more powerful prospect is that such quantum technologies could out-perform any future iteration of their classical counterparts, no matter how well the attributes of those classical strategies can be improved. Here, for optical direct absorption measurement, we experimentally demonstrate such an instance of an absolute advantage per photon probe that is exposed to the absorbative sample. We use correlated intensity measurements of spontaneous parametric downconversion using a commercially available air-cooled CCD, a new estimator for data analysis and a high heralding efficiency photon-pair source. We show this enables improvement in the precision of measurement, per photon probe, beyond what is achievable with an ideal coherent state (a perfect laser) detected with 100% efficient and noiseless detection. We see this absolute improvement for up to 50% absorption, with a maximum observed factor of improvement of 1.46. This equates to around 32% reduction in the total number of photons traversing an optical sample, compared to any future direct optical absorption measurement using classical light.
We investigated precision measurements in a two-level system coupled to a single-photon-added coherent state (SPACS) under postselected weak measurement. We analyzed strategies for improving measurement precision, including parameter estimation and the signal-to-noise ratio (SNR) in postselected weak measurements, using the photon statistics of SPACS as the meter. Our results demonstrate that SPACS-based postselected weak measurements can outperform conventional measurement schemes in terms of precision. Additionally, we explicitly introduced an alternative weak measurement method, which is commonly applied in dispersive light-atom interactions. Our work presents a novel approach to addressing fundamental issues in quantum precision measurement based on photon statistics, and it provides a method for extracting the photon and phase shifts of radiation fields through the weak values of system observables.