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:2601.15565

Bright Pulsed Squeezed Light for Quantum-Enhanced Precision Microscopy

Alex Terrasson, Lars Madsen, Joel Grim, Warwick Bowen

quant-phphysics.opticsSubmitted Jan 22, 2026• Announced Jan 23, 2026• 0 citations
arXivHTMLPDF

Abstract

Squeezed states of light enable enhanced measurement precision by reducing noise below the standard quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a $χ^2$ optical parametric amplification process in a waveguide. We measure $-3.2~\mathrm{dB}$ of bright squeezing with optical power compatible with nonlinear microscopy, as well as $-3.6~\mathrm{dB}$ of vacuum squeezing. Corrected for losses, these squeezing levels correspond to $-15.4^{+2.7}_{-8.7}~\mathrm{dB}$ of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of quantum-enhanced nonlinear microscopy in biological studies.

Comments
5 pages, 3 figures

Related papers

Pulsed squeezed light: characterization and applications

Triginer Garcés, Gil

Squeezed light is expected to enable new quantum metrology and quantum computation applications, but the very high degree of experimental control required in practice places severe demands on the physical devices used to generate it. As ultrafast squeezed light sources are reaching an unprecedented degree of brightness and modal control, there is a strong interest in developing methods for their experimental characterization and theoretical understanding. In this thesis, we demonstrate both a new application and a new characterization technique for pulsed squeezed light. In the first part of the thesis, we present a new metrological application of pulsed squeezed light: quantum-enhanced label-free nonlinear microscopy. Stimulated emission microscopy (SEM) is a state-of-the-art pump-probe microscopy technique whose sensitivity is ultimately limited by shot noise in the probe beam. We propose to overcome this fundamental limitation by using a sub-Poissonian probe generated via optical parametric amplification. We demonstrate an intensity-squeezed sub-picosecond pulsed probe, and a simple stimulated emission microscope. Using this squeezed probe, sub-Poissonian statistics are observed in the SEM signal. After this proof-of-principle experiment, we aim to provide an improved design for a source of intensity-squeezed light. First, we develop a theoretical framework to simulate the photon statistics of a general sub-Poissonian source, considering pulsed and focused pump and seed fields in a unified spatio-temporal description. Next, we use this framework to suggest possible improvements to our previous squeezed probe. In the second part of this thesis, we provide new theoretical and experimental tools to analyze the high gain regime of pulsed spontaneous parametric down-conversion (SPDC). We study a waveguided source capable of generating twin-beams with tens of photons in a single spatio-temporal mode. We develop a framework to efficiently simulate SPDC for an arbitrary nonlinear gain, including the effect of parasitic nonlinearities such as self-phase modulation (SPM) of the pump and cross-phase modulation (XPM) between pump and twin-beams. We experimentally characterize our source using a new technique based on stimulated difference-frequency generation (DFG). In a type-II down-conversion process, we measure the frequency generation produced not only in the orthogonal polarization to the seeding beam, but also in its same polarization, which we interpret as cascaded difference-frequency generation. We argue that the additional information obtained in this measurement allows for a self-referenced estimation of the squeezing gain. Using these measurements, we accurately fit our theoretical model, revealing that, in the high gain regime, parasitic nonlinearities strongly affect the spectral structure of the twin-beams. We propose a simple strategy to reduce the impact of these nonlinearities on the modal structure of SPDC.

•Jan 1, 2019•0 citations

Fast biological imaging with quantum-enhanced Raman microscopy

Alex Terrasson, Nicolas P. Mauranyapin, Catxere A. Casacio +5 more

Stimulated Raman scattering (SRS) microscopy is a powerful label-free imaging technique that probes the vibrational response of chemicals with high specificity and sensitivity. High-power, quantum-enhanced SRS microscopes have been recently demonstrated and applied to polymers and biological samples. Quantum correlations, in the form of squeezed light, enable the microscopes to operate below the shot noise limit, enhancing their performance without increasing the illumination intensity. This addresses the signal-to-noise ratio (SNR) and speed constraints introduced by photodamage in shot noise-limited microscopes. Previous microscopes have either used single-beam squeezing, but with insufficient brightness to reach the optimal ratio of pump-to-Stokes intensity for maximum SNR, or have used twin-beam squeezing and suffered a 3 dB noise penalty. Here we report a quantum-enhanced Raman microscope that uses a bright squeezed single-beam, enabling operation at the optimal efficiency of the SRS process. The increase in brightness leads to multimode effects that degrade the squeezing level, which we partially overcome using spatial filtering. We apply our quantum-enhanced SRS microscope to biological samples and demonstrate quantum-enhanced multispectral imaging of living cells. The imaging speed of 100×100 pixels in 18 seconds allows the dynamics of cell organelles to be resolved. The SNR achieved is compatible with video-rate imaging, with the quantum correlations yielding a 20% improvement in imaging speed compared to shot noise-limited operation.

arXiv:2403.10077•Optics Express•Jun 21, 2024•16 citations

Highly efficient measurement of optical quadrature squeezing using a spatial light modulator controlled by machine learning

Jorge Amari, Junnosuke Takai, Takuya Hirano

Pulsed squeezed light is a key resource for many quantum information processing tasks. Among the various methods for generating squeezed light, single-pass parametric amplification has various advantages such as broad bandwidth, compactness, and stability. The challenge in achieving high-level pulsed squeezing has been to improve detection efficiency. We used a spatial light modulator controlled by machine learning to improve the spatial mode matching between the local oscillator and squeezed light. We achieved pulsed squeezing of 5.88 dB generated by optical parametric amplification in a waveguide. To the best of our knowledge, this is the highest obtained pulsed squeezing, and we believe this achievement will lead to more compact and efficient quantum information technology.

Optics Continuum•Mar 7, 2023•8 citations

Generation and time-domain characterization of picosecond pulsed squeezed vacuum from a Ti:sapphire-laser-pumped periodically poled lithium niobate waveguide

Zicong Xu, Kenichi Oguchi, Sho Nitanai +1 more

In recent years, quantum technology has expanded its reach across a wide range of fields. Pulsed squeezing, in particular, holds significant promise for advancing quantum-enhanced nonlinear microscopy as well as high-speed quantum computing and communication. However, the performance of pulsed squeezing using the widely adopted Ti:sapphire laser has been rarely investigated, especially in the picosecond regime. Here, we report record-level picosecond pulsed squeezing of -4.41 dB generated with a Ti:sapphire laser, together with a method for time-domain phase characterization of picosecond pulsed squeezed light. We anticipate that these results will promote the broader adoption of quantum systems based on the versatile, broadband-tunable Ti:sapphire platform and foster a deeper understanding of pulsed squeezed light.

Optics Express•Dec 15, 2025•0 citations

Broadly tunable quantum-enhanced Raman microscopy for advancing bioimaging

Dmitrii Akatev, Yijian Meng, Jonathan Brewer +3 more

Stimulated Raman scattering (SRS) microscopy has emerged as a powerful technique for probing the spatiotemporal dynamics of molecular bonds with exceptional sensitivity, resolution, and speed. However, classically, its performance remains fundamentally constrained by optical shot noise, which imposes a strict limit on detection sensitivity and speed. Here, we demonstrate a quantum-enhanced SRS microscopy platform that circumvents this barrier by harnessing amplitude-squeezed light. Specifically, we generate a Stokes beam with $5.2~\mathrm{dB}$ of amplitude squeezing using traveling-wave optical parametric amplification in second-order nonlinear waveguides, and combine it with a tunable coherent pump to access vibrational modes spanning from $1000$ to $3100~\mathrm{cm}^{-1}$. Applied to quantum imaging of metabolites in biological tissue (pork muscle), our quantum-enhanced Raman microscope achieves an average noise suppression of $3.6~\mathrm{dB}$ and a $51\%$ enhancement in signal-to-noise ratio (SNR) -- to the best of our knowledge, the largest improvement reported to date in quantum-enhanced SRS microscopy of biological samples.

physics.opticsCross-listedarXiv:2511.01430•Optica Quantum•Nov 4, 2025•3 citations

Quantum enhanced microscopy

Catxere A. Casacio

In optical microscopy, as in any biological measurement performed with light, there is a compromise between increasing power to improve resolution and decreasing power to prevent photodamage to the biological structure. Quantum optics allows this compromise to be overcome, enabling improved precision without increased illumination intensity. This thesis demonstrates, for the first time, absolute quantum advantage in microscopy, with a specific focus on Stimulated Raman Scattering (SRS) microscopy.SRS microscopy is a powerful tool widely used in many fields, especially in biomedical sciences. It uses a two-photon process where the light is downshifted in frequency by being absorbed and subsequently inelastically scattered by the intrinsic molecular vibrations in the sample. Each element or molecule has a different response, allowing selective imaging of biological systems. SRS microscopy is particularly useful because it is label-free (no addition of dyes, beads or any implanted tracer), meaning that imaging contrast is achieved without modification of, or interference with, the specimen. Here I present our newly built state-of-the-art shot-noise limited SRS microscope. I also characterize the Raman microscope, describe the developped imaging system and show SRS spectroscopy and imaging of both polystyrene beads and living yeast cells.The quantisation of light introduces a fundamental uncertainty, or quantum noise, in both the amplitude and phase quadratures of an optical field. A squeezed state of light is a state of the optical field where the uncertainty of one of these quadratures is reduced below the quantum noise. Therefore, it provides an approach to reduce the noise level below this quantum noise limit and consequently increases measured signal-to-noise ratio. Here I describe the concepts involved in this technique and present our newly built light squeezer. I characterize the squeezing and show up to -1.3 dB of noise floor reduction for a 6 picosecond pulsed laser, which is the pulse duration that maximises the Raman interaction.In this thesis we apply squeezed states of light in SRS, developping a quantum-enhanced micro- scope. Our SRS Raman intensity noise is ∆I/I ≈ 10^(−7) and the measured quantum efficiency of the built photodiode is η = 72%. In this proof of principle we show a reduction of the noise floor of at least 13% below the quantum noise limit for Raman imaging of polystyrene beads and living yeast cells. This enhancement allowed us to resolve the cell membrane where with conventional microscope would be unresolvable. It also allowed sub-micron spatial resolution. The improved image contrast and reduced imaging time, while avoiding photodamage in the sample, surpasses the current state-of-the-art Raman microscopes and opens opportunities for new discoveries in biophysics.

•Feb 17, 2021•1 citation
Squeezed states of light enable enhanced measurement precision by reducing noise below the standard quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a χ2χ^2χ2 optical parametric amplification process in a waveguide. We measure −3.2 dB-3.2~\mathrm{dB}−3.2 dB of bright squeezing with optical power compatible with nonlinear microscopy, as well as −3.6 dB-3.6~\mathrm{dB}−3.6 dB of vacuum squeezing. Corrected for losses, these squeezing levels correspond to −15.4−8.7+2.7 dB-15.4^{+2.7}_{-8.7}~\mathrm{dB}−15.4−8.7+2.7​ dB of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of quantum-enhanced nonlinear microscopy in biological studies.
Squeezed light is expected to enable new quantum metrology and quantum computation applications, but the very high degree of experimental control required in practice places severe demands on the physical devices used to generate it. As ultrafast squeezed light sources are reaching an unprecedented degree of brightness and modal control, there is a strong interest in developing methods for their experimental characterization and theoretical understanding. In this thesis, we demonstrate both a new application and a new characterization technique for pulsed squeezed light. In the first part of the thesis, we present a new metrological application of pulsed squeezed light: quantum-enhanced label-free nonlinear microscopy. Stimulated emission microscopy (SEM) is a state-of-the-art pump-probe microscopy technique whose sensitivity is ultimately limited by shot noise in the probe beam. We propose to overcome this fundamental limitation by using a sub-Poissonian probe generated via optical parametric amplification. We demonstrate an intensity-squeezed sub-picosecond pulsed probe, and a simple stimulated emission microscope. Using this squeezed probe, sub-Poissonian statistics are observed in the SEM signal. After this proof-of-principle experiment, we aim to provide an improved design for a source of intensity-squeezed light. First, we develop a theoretical framework to simulate the photon statistics of a general sub-Poissonian source, considering pulsed and focused pump and seed fields in a unified spatio-temporal description. Next, we use this framework to suggest possible improvements to our previous squeezed probe. In the second part of this thesis, we provide new theoretical and experimental tools to analyze the high gain regime of pulsed spontaneous parametric down-conversion (SPDC). We study a waveguided source capable of generating twin-beams with tens of photons in a single spatio-temporal mode. We develop a framework to efficiently simulate SPDC for an arbitrary nonlinear gain, including the effect of parasitic nonlinearities such as self-phase modulation (SPM) of the pump and cross-phase modulation (XPM) between pump and twin-beams. We experimentally characterize our source using a new technique based on stimulated difference-frequency generation (DFG). In a type-II down-conversion process, we measure the frequency generation produced not only in the orthogonal polarization to the seeding beam, but also in its same polarization, which we interpret as cascaded difference-frequency generation. We argue that the additional information obtained in this measurement allows for a self-referenced estimation of the squeezing gain. Using these measurements, we accurately fit our theoretical model, revealing that, in the high gain regime, parasitic nonlinearities strongly affect the spectral structure of the twin-beams. We propose a simple strategy to reduce the impact of these nonlinearities on the modal structure of SPDC.
Stimulated Raman scattering (SRS) microscopy is a powerful label-free imaging technique that probes the vibrational response of chemicals with high specificity and sensitivity. High-power, quantum-enhanced SRS microscopes have been recently demonstrated and applied to polymers and biological samples. Quantum correlations, in the form of squeezed light, enable the microscopes to operate below the shot noise limit, enhancing their performance without increasing the illumination intensity. This addresses the signal-to-noise ratio (SNR) and speed constraints introduced by photodamage in shot noise-limited microscopes. Previous microscopes have either used single-beam squeezing, but with insufficient brightness to reach the optimal ratio of pump-to-Stokes intensity for maximum SNR, or have used twin-beam squeezing and suffered a 3 dB noise penalty. Here we report a quantum-enhanced Raman microscope that uses a bright squeezed single-beam, enabling operation at the optimal efficiency of the SRS process. The increase in brightness leads to multimode effects that degrade the squeezing level, which we partially overcome using spatial filtering. We apply our quantum-enhanced SRS microscope to biological samples and demonstrate quantum-enhanced multispectral imaging of living cells. The imaging speed of 100×100 pixels in 18 seconds allows the dynamics of cell organelles to be resolved. The SNR achieved is compatible with video-rate imaging, with the quantum correlations yielding a 20% improvement in imaging speed compared to shot noise-limited operation.
Pulsed squeezed light is a key resource for many quantum information processing tasks. Among the various methods for generating squeezed light, single-pass parametric amplification has various advantages such as broad bandwidth, compactness, and stability. The challenge in achieving high-level pulsed squeezing has been to improve detection efficiency. We used a spatial light modulator controlled by machine learning to improve the spatial mode matching between the local oscillator and squeezed light. We achieved pulsed squeezing of 5.88 dB generated by optical parametric amplification in a waveguide. To the best of our knowledge, this is the highest obtained pulsed squeezing, and we believe this achievement will lead to more compact and efficient quantum information technology.
In recent years, quantum technology has expanded its reach across a wide range of fields. Pulsed squeezing, in particular, holds significant promise for advancing quantum-enhanced nonlinear microscopy as well as high-speed quantum computing and communication. However, the performance of pulsed squeezing using the widely adopted Ti:sapphire laser has been rarely investigated, especially in the picosecond regime. Here, we report record-level picosecond pulsed squeezing of -4.41 dB generated with a Ti:sapphire laser, together with a method for time-domain phase characterization of picosecond pulsed squeezed light. We anticipate that these results will promote the broader adoption of quantum systems based on the versatile, broadband-tunable Ti:sapphire platform and foster a deeper understanding of pulsed squeezed light.
Stimulated Raman scattering (SRS) microscopy has emerged as a powerful technique for probing the spatiotemporal dynamics of molecular bonds with exceptional sensitivity, resolution, and speed. However, classically, its performance remains fundamentally constrained by optical shot noise, which imposes a strict limit on detection sensitivity and speed. Here, we demonstrate a quantum-enhanced SRS microscopy platform that circumvents this barrier by harnessing amplitude-squeezed light. Specifically, we generate a Stokes beam with 5.2 dB5.2~\mathrm{dB}5.2 dB of amplitude squeezing using traveling-wave optical parametric amplification in second-order nonlinear waveguides, and combine it with a tunable coherent pump to access vibrational modes spanning from 100010001000 to 3100 cm−13100~\mathrm{cm}^{-1}3100 cm−1. Applied to quantum imaging of metabolites in biological tissue (pork muscle), our quantum-enhanced Raman microscope achieves an average noise suppression of 3.6 dB3.6~\mathrm{dB}3.6 dB and a 51%51\%51% enhancement in signal-to-noise ratio (SNR) -- to the best of our knowledge, the largest improvement reported to date in quantum-enhanced SRS microscopy of biological samples.
In optical microscopy, as in any biological measurement performed with light, there is a compromise between increasing power to improve resolution and decreasing power to prevent photodamage to the biological structure. Quantum optics allows this compromise to be overcome, enabling improved precision without increased illumination intensity. This thesis demonstrates, for the first time, absolute quantum advantage in microscopy, with a specific focus on Stimulated Raman Scattering (SRS) microscopy.SRS microscopy is a powerful tool widely used in many fields, especially in biomedical sciences. It uses a two-photon process where the light is downshifted in frequency by being absorbed and subsequently inelastically scattered by the intrinsic molecular vibrations in the sample. Each element or molecule has a different response, allowing selective imaging of biological systems. SRS microscopy is particularly useful because it is label-free (no addition of dyes, beads or any implanted tracer), meaning that imaging contrast is achieved without modification of, or interference with, the specimen. Here I present our newly built state-of-the-art shot-noise limited SRS microscope. I also characterize the Raman microscope, describe the developped imaging system and show SRS spectroscopy and imaging of both polystyrene beads and living yeast cells.The quantisation of light introduces a fundamental uncertainty, or quantum noise, in both the amplitude and phase quadratures of an optical field. A squeezed state of light is a state of the optical field where the uncertainty of one of these quadratures is reduced below the quantum noise. Therefore, it provides an approach to reduce the noise level below this quantum noise limit and consequently increases measured signal-to-noise ratio. Here I describe the concepts involved in this technique and present our newly built light squeezer. I characterize the squeezing and show up to -1.3 dB of noise floor reduction for a 6 picosecond pulsed laser, which is the pulse duration that maximises the Raman interaction.In this thesis we apply squeezed states of light in SRS, developping a quantum-enhanced micro- scope. Our SRS Raman intensity noise is ∆I/I ≈ 10^(−7) and the measured quantum efficiency of the built photodiode is η = 72%. In this proof of principle we show a reduction of the noise floor of at least 13% below the quantum noise limit for Raman imaging of polystyrene beads and living yeast cells. This enhancement allowed us to resolve the cell membrane where with conventional microscope would be unresolvable. It also allowed sub-micron spatial resolution. The improved image contrast and reduced imaging time, while avoiding photodamage in the sample, surpasses the current state-of-the-art Raman microscopes and opens opportunities for new discoveries in biophysics.