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arXiv:2001.00422 · Physical Review Research

Lifetime and polarization for real and virtual correlated Stokes-anti-Stokes Raman scattering in diamond

Filomeno Soares de Aguiar Júnior, Marcelo França Santos, Carlos Henrique Monken, Ado Jório

Published Jan 27, 2020• 17 citations
arXivHTMLPDF

Abstract

The correlation between the Stokes and anti-Stokes components of Raman scattering has assumed an important role in the field of quantum information. When the Raman shifts match the energy of a phonon in the material, in the real-SaS, one-phonon Fock state are generated. When such resonance is not achieved, the energy exchange is mediated by virtual phonons, generating photonic Cooper pairs (PCPs). In this work, investigations of polarization correlations and scattering time dependences elucidate the fundamental difference between the real and the virtual phenomena.

DOI
10.1103/physrevresearch.2.013084

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Quantum correlations in the Stokes and anti-Stokes Raman scattering: the photonic counterparts of Cooper pairs

Filomeno Soares de Aguiar Júnior

The correlated Raman scattering, referred to here as the SaS process, occurs with the annihilation, within a material, of two photons of an excitation laser and the creation of a quantum correlated Stokes (S) and anti-Soktes (aS) photon pair where the phonon created in the S process is annihilated in the aS scattering. We found that, in addition to real SaS process where the energy exchange coincides with the energy of a vibrational state of the material, there is also the virtual SaS process, whose the exchange of energy and momentum between the photons of the laser, generating the S-aS photon pair, is mediated by a virtual vibrational excitation, setting up a photon-photon interaction similar to the electron-electron attraction responsible for the creation of Cooper pairs of the BCS theory of superconductivity. We observed the SaS process in transparent media in general, by measuring non-classical values of the normalized second-order cross-correlation function of the Stokes and anti-Stokes fields, 2(0). In diamond, we characterize the intensity of the virtual SaS scattering ( ) as a function of the virtual phonon energy, proving that the SaS process occurs only when the photon-photon interaction is attractive, as in the BCS theory for the Cooper pairs. We show that photons S and aS from the SaS process are scattered predominantly in the same polarization as the excitation laser of the sample and, with this, we implemented the pump-probe technique to study the lifetime of the real phonon (obtained in the diamond order 2.8 ps ) and the lifetime of the virtual excitation, which proved to be inferior to the temporal resolution of the measurement’s, characterizing one of the main differences between the two processes. We also observed that, due to the relations of energy and momentum conservation, have the same spatial intensity profile of the non-interacting laser that crosses the sample, different from the behavior observed for uncorrelated Raman scattering which spreads photons in all directions. We observed that the efficiency of the SaS scattering is proportional to the Raman scattering cross-section when we compare the process in different hydrocarbons and we generalize the observations made in the diamond to the sample of liquid decane. In water, the values of 2(0), predicted by the theoretical description of the process, corroborate the experimental data, validating the BCS theory for virtual SaS scattering, setting the pair of Stokes and anti-Stokes photons as counterparts of the Cooper pairs.

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Photons can interact with each other in condensed matter by exchanging virtual phonons, via instantaneous Stokes and anti-Stokes Raman scattering. We study this phenomenon and its analogy to the formation of Cooper pairs in superconductivity.

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Degenerate four-wave mixing in diamond generates a quantum state ${\ensuremath{\rho}}_{\mathrm{SaS}}$ composed of Stokes (S) and anti-Stokes (aS) time-correlated photon pairs (SaS). Here, polarization state tomography of ${\ensuremath{\rho}}_{\mathrm{SaS}}$ is performed in four pertinent scattering configurations: Raman shift in resonance and out of resonance with the phonon energy, and incident light polarized in the direction parallel to or $\ensuremath{\pi}/4$ rotated from a diamond crystallographic axis. We reconstruct the density matrix, calculate concurrence and purity for the four configurations, and directly measure and analyze the diagonal terms of ${\ensuremath{\rho}}_{\mathrm{SaS}}$ in different bases. We establish ${\ensuremath{\rho}}_{\mathrm{SaS}}$ as an entangled linear combination of electronic four-wave mixing and SaS Raman process, mixed with uncorrelated S and aS photons, with the weight constants depending on the scattering conditions, which can be engineered for future applications.

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Arthur Patrocínio Pena

In this work, the Stokes-anti-Stokes¿ time-correlation phenomena was studied. The timecorrelated scattering process occurs when the same vibrational quantum from a material participates in the Stokes and anti-Stokes photon generation process in the inelastic scattering of light. We demonstrate that the SaS phenomenon occurs in different bands of the Raman spectra, from different transparent liquid materials. The observation of time-correlated SaS pairs in energy bands out of the resonance region indicates the possibility of energy exchange between photons via virtual phonons, which allows drawing a parallel with the Cooper pair formation phenomenon for electrons, from the BCS superconductivity theory. In this dissertation, we discuss the fundamentals of the theory and the instrumentation related to the concepts about the discussed phenomena, as well as demonstrate that the rate of SaS pair formation exhibits a linear relation with the supertransparency gap, concept brought from the BCS superconductivity theory.

•Mar 15, 2018•0 citations

Properties of nonclassical correlated Stokes–anti-Stokes photon pair in decane

Filomeno Soares de Aguiar Júnior, Carlos Henrique Monken, Ado Jório

In this study, the correlated Stokes--anti-Stokes Raman scattering, denominated as the SaS process, is investigated in a decane sample, generalizing for a liquid the results observed in crystalline diamond. The production of SaS photon pairs is observed in both real and virtual processes by measuring nonclassical values of the second-order cross-correlation function ${g}_{\text{SaS}}^{2}(0)$. The correlated Raman spectrum is observed only for Raman shift values below approximately $2900\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, which is equivalent to the highest vibrational mode of the decane molecule. Furthermore, despite the fact that decane is a liquid, the polarization and spatial profile of the SaS process in decane presents the same properties as those observed in diamond.

Physical review. B./Physical review. B•Jan 9, 2024•0 citations
The correlation between the Stokes and anti-Stokes components of Raman scattering has assumed an important role in the field of quantum information. When the Raman shifts match the energy of a phonon in the material, in the real-SaS, one-phonon Fock state are generated. When such resonance is not achieved, the energy exchange is mediated by virtual phonons, generating photonic Cooper pairs (PCPs). In this work, investigations of polarization correlations and scattering time dependences elucidate the fundamental difference between the real and the virtual phenomena.
The correlated Raman scattering, referred to here as the SaS process, occurs with the annihilation, within a material, of two photons of an excitation laser and the creation of a quantum correlated Stokes (S) and anti-Soktes (aS) photon pair where the phonon created in the S process is annihilated in the aS scattering. We found that, in addition to real SaS process where the energy exchange coincides with the energy of a vibrational state of the material, there is also the virtual SaS process, whose the exchange of energy and momentum between the photons of the laser, generating the S-aS photon pair, is mediated by a virtual vibrational excitation, setting up a photon-photon interaction similar to the electron-electron attraction responsible for the creation of Cooper pairs of the BCS theory of superconductivity. We observed the SaS process in transparent media in general, by measuring non-classical values of the normalized second-order cross-correlation function of the Stokes and anti-Stokes fields, 2(0). In diamond, we characterize the intensity of the virtual SaS scattering ( ) as a function of the virtual phonon energy, proving that the SaS process occurs only when the photon-photon interaction is attractive, as in the BCS theory for the Cooper pairs. We show that photons S and aS from the SaS process are scattered predominantly in the same polarization as the excitation laser of the sample and, with this, we implemented the pump-probe technique to study the lifetime of the real phonon (obtained in the diamond order 2.8 ps ) and the lifetime of the virtual excitation, which proved to be inferior to the temporal resolution of the measurement’s, characterizing one of the main differences between the two processes. We also observed that, due to the relations of energy and momentum conservation, have the same spatial intensity profile of the non-interacting laser that crosses the sample, different from the behavior observed for uncorrelated Raman scattering which spreads photons in all directions. We observed that the efficiency of the SaS scattering is proportional to the Raman scattering cross-section when we compare the process in different hydrocarbons and we generalize the observations made in the diamond to the sample of liquid decane. In water, the values of 2(0), predicted by the theoretical description of the process, corroborate the experimental data, validating the BCS theory for virtual SaS scattering, setting the pair of Stokes and anti-Stokes photons as counterparts of the Cooper pairs.
Degenerate four-wave mixing in diamond generates a quantum state ${\ensuremath{\rho}}_{\mathrm{SaS}}$ composed of Stokes (S) and anti-Stokes (aS) time-correlated photon pairs (SaS). Here, polarization state tomography of ${\ensuremath{\rho}}_{\mathrm{SaS}}$ is performed in four pertinent scattering configurations: Raman shift in resonance and out of resonance with the phonon energy, and incident light polarized in the direction parallel to or $\ensuremath{\pi}/4$ rotated from a diamond crystallographic axis. We reconstruct the density matrix, calculate concurrence and purity for the four configurations, and directly measure and analyze the diagonal terms of ${\ensuremath{\rho}}_{\mathrm{SaS}}$ in different bases. We establish ${\ensuremath{\rho}}_{\mathrm{SaS}}$ as an entangled linear combination of electronic four-wave mixing and SaS Raman process, mixed with uncorrelated S and aS photons, with the weight constants depending on the scattering conditions, which can be engineered for future applications.
In this work, the Stokes-anti-Stokes¿ time-correlation phenomena was studied. The timecorrelated scattering process occurs when the same vibrational quantum from a material participates in the Stokes and anti-Stokes photon generation process in the inelastic scattering of light. We demonstrate that the SaS phenomenon occurs in different bands of the Raman spectra, from different transparent liquid materials. The observation of time-correlated SaS pairs in energy bands out of the resonance region indicates the possibility of energy exchange between photons via virtual phonons, which allows drawing a parallel with the Cooper pair formation phenomenon for electrons, from the BCS superconductivity theory. In this dissertation, we discuss the fundamentals of the theory and the instrumentation related to the concepts about the discussed phenomena, as well as demonstrate that the rate of SaS pair formation exhibits a linear relation with the supertransparency gap, concept brought from the BCS superconductivity theory.
In this study, the correlated Stokes--anti-Stokes Raman scattering, denominated as the SaS process, is investigated in a decane sample, generalizing for a liquid the results observed in crystalline diamond. The production of SaS photon pairs is observed in both real and virtual processes by measuring nonclassical values of the second-order cross-correlation function gSaS2(0){g}_{\text{SaS}}^{2}(0)gSaS2​(0). The correlated Raman spectrum is observed only for Raman shift values below approximately $2900\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, which is equivalent to the highest vibrational mode of the decane molecule. Furthermore, despite the fact that decane is a liquid, the polarization and spatial profile of the SaS process in decane presents the same properties as those observed in diamond.