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Schlawin F. Two-photon absorption cross sections of pulsed entangled beams. J Chem Phys 2024; 160:144117. [PMID: 38619059 DOI: 10.1063/5.0196817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 03/24/2024] [Indexed: 04/16/2024] Open
Abstract
Entangled two-photon absorption (ETPA) could form the basis of nonlinear quantum spectroscopy at very low photon fluxes, since, at sufficiently low photon fluxes, ETPA scales linearly with the photon flux. When different pairs start to overlap temporally, accidental coincidences are thought to give rise to a "classical" quadratic scaling that dominates the signal at large photon fluxes and, thus, recovers a supposedly classical regime, where any quantum advantage is thought to be lost. Here, we scrutinize this assumption and demonstrate that quantum-enhanced absorption cross sections can persist even for very large photon numbers. To this end, we use a minimal model for quantum light, which can interpolate continuously between the entangled pair and a high-photon-flux limit, to analytically derive ETPA cross sections and the intensity crossover regime. We investigate the interplay between spectral and spatial degrees of freedom and how linewidth broadening of the sample impacts the experimentally achievable enhancement.
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Affiliation(s)
- Frank Schlawin
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany; University of Hamburg, Luruper Chaussee 149, Hamburg, Germany; and The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany
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Gelin MF, Chen L, Domcke W. Equation-of-Motion Methods for the Calculation of Femtosecond Time-Resolved 4-Wave-Mixing and N-Wave-Mixing Signals. Chem Rev 2022; 122:17339-17396. [PMID: 36278801 DOI: 10.1021/acs.chemrev.2c00329] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Femtosecond nonlinear spectroscopy is the main tool for the time-resolved detection of photophysical and photochemical processes. Since most systems of chemical interest are rather complex, theoretical support is indispensable for the extraction of the intrinsic system dynamics from the detected spectroscopic responses. There exist two alternative theoretical formalisms for the calculation of spectroscopic signals, the nonlinear response-function (NRF) approach and the spectroscopic equation-of-motion (EOM) approach. In the NRF formalism, the system-field interaction is assumed to be sufficiently weak and is treated in lowest-order perturbation theory for each laser pulse interacting with the sample. The conceptual alternative to the NRF method is the extraction of the spectroscopic signals from the solutions of quantum mechanical, semiclassical, or quasiclassical EOMs which govern the time evolution of the material system interacting with the radiation field of the laser pulses. The NRF formalism and its applications to a broad range of material systems and spectroscopic signals have been comprehensively reviewed in the literature. This article provides a detailed review of the suite of EOM methods, including applications to 4-wave-mixing and N-wave-mixing signals detected with weak or strong fields. Under certain circumstances, the spectroscopic EOM methods may be more efficient than the NRF method for the computation of various nonlinear spectroscopic signals.
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Affiliation(s)
- Maxim F Gelin
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Lipeng Chen
- Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany
| | - Wolfgang Domcke
- Department of Chemistry, Technical University of Munich, D-85747 Garching,Germany
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Li T, Li F, Liu X, Yakovlev VV, Agarwal GS. Quantum-enhanced stimulated Brillouin scattering spectroscopy and imaging. OPTICA 2022; 9:959-964. [PMID: 37398895 PMCID: PMC10312138 DOI: 10.1364/optica.467635] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 07/14/2022] [Indexed: 07/04/2023]
Abstract
Brillouin microscopy is an emerging label-free imaging technique used to assess local viscoelastic properties. Quantum-enhanced stimulated Brillouin scattering is demonstrated using low power continuous-wave lasers at 795 nm. A signal-to-noise ratio enhancement of 3.4 dB is reported by using two-mode intensity-difference squeezed light generated with the four-wave mixing process in atomic rubidium vapor. The low optical power and the excitation wavelengths in the water transparency window have the potential to provide a powerful bio-imaging technique for probing mechanical properties of biological samples prone to phototoxicity and thermal effects. The performance enhancement affordable through the use of quantum light may pave the way for significantly improved sensitivity that cannot be achieved classically. The proposed method for utilizing squeezed light for enhanced stimulated Brillouin scattering can be easily adapted for both spectroscopic and imaging applications in biology.
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Affiliation(s)
- Tian Li
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Chemistry and Physics, The University of Tennessee at Chattanooga, Chattanooga, Tennessee 37403, USA
| | - Fu Li
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
| | - Xinghua Liu
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
| | - Vladislav V. Yakovlev
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas 77843, USA
| | - Girish S. Agarwal
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas 77843, USA
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA
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The path toward quantum advantage in optical spectroscopy of materials. Proc Natl Acad Sci U S A 2021; 118:2112897118. [PMID: 34465628 DOI: 10.1073/pnas.2112897118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Abstract
Quantum light and its statistics provide powerful tools for the study of properties of matter that are difficult to retrieve with classical light. Novel spectroscopic and sensing techniques based on quantum light sources can reveal information about complex material systems that is not accessible by varying the frequencies or time delays of classical light pulses. Here, based on a four-wave mixing process, we report an experimental study of the 2D quantum noise spectra of two-beam intensity difference squeezing. External noise erodes the resolution of classical measurements, while quantum signals remain intact. Our results pave the way for exploiting quantum correlations of squeezed light for spectroscopic applications. Four-wave mixing (FWM) of optical fields has been extensively used in quantum information processing, sensing, and memories. It also forms a basis for nonlinear spectroscopies such as transient grating, stimulated Raman, and photon echo where phase matching is used to select desired components of the third-order response of matter. Here we report an experimental study of the two-dimensional quantum noise intensity difference spectra of a pair of squeezed beams generated by FWM in hot Rb vapor. The measurement reveals details of the χ(3) susceptibility dressed by the strong pump field which induces an AC Stark shift, with higher spectral resolution compared to classical measurements of probe and conjugate beam intensities. We demonstrate how quantum correlations of squeezed light can be utilized as a spectroscopic tool which unlike their classical counterparts are robust to external noise.
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