Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - INCEPT (INhomogenieties and fluctuations in quantum CohErent matter Phases by ultrafast optical Tomography)

Teaser

The main objective of the project is to develop a new class of time domain spectroscopies where the spectroscopic information is retrieved from non-classical statistical features of light rather than mean value properties as in standard spectroscopic approaches. In the first...

Summary

The main objective of the project is to develop a new class of time domain spectroscopies where the spectroscopic information is retrieved from non-classical statistical features of light rather than mean value properties as in standard spectroscopic approaches. In the first part of the project, we have set the bases, experimental and theoretical, to develop such a new class of spectroscopic probes. Our approach is giving particularly rewarding results. In particular, in spite of the infancy of our approach, we already have preliminary results, reported in different scientific contributions in the past 2 years, that set the bases to understand how photon number fluctuation and multimode optical correlations carry information on the intrinsic fluctuation of the material.
The rationale guiding us is that in striking contrast to standard optical techniques, which always measure the integrated photon number impinging on the sample and reflected (transmitted) by it, we propose that a full characterization of the statistical properties of light priory and subsequently to the interaction with the material provide a much richer spectroscopic information. In order to test this hypothesis, we worked on different single shot detection scheme which allow for the measurements of the photon number fluctuations (frequency integrated and frequency-resolved). The first results are very promising. In a recent manuscript which have been published recently (Physical Review Letters 119, 187403 (2017)) we set the bases for unveiling the spectroscopic significance of integrated photon number fluctuation in time domain experiment.
Regarding frequency resolved fluctuations and coherent vibrational modes in electronic ground states we have developed a theoretical framework treat effectively the interaction between photonic and phononic degrees of freedom in time domain experiment (New J. Phys. 19, 023032, 2017 and EPJ Quantum Technol. (2016) 3: 7) and more recently to extend this approach to frequency-resolved measurements (https://arxiv.org/abs/1810.11399).

Work performed

Our fundamental research is across the research fields of material science and quantum information. As testified by various research programs from different funding agencies (Quantera flagship, EPSRC quantum technology program) one of the major technological and scientific challenges emerging in the last decade is understanding how we can harness the properties of quantum mechanics for technological purposes. In this context, the preliminary results obtained in INCEPT stand out as a paradigmatic change in the approach to non-equilibrium physics. This could have an impact on both our comprehension of quantum materials as well as in information technology. The positive outcome of the project activities carried out up to now is testified by the high profile of our publications and a large number of invited contributions to the major conferences the team members received.

So far, our work was mainly devoted to the set-up of the spectroscopies as well as to set the bases for unveiling the spectroscopic significance of integrated photon number fluctuation in time domain experiment. We also have developed a theoretical framework which treats effectively the interaction between photonic and photonic degrees of freedom in time domain experiment and we have recently worked on extending this approach to frequency-resolved measurements. The work performed lead us to an important theoretical understanding, i.e., that even classical intensity fluctuation can be beneficial in terms of the spectroscopic information they deliver. Guided by this idea we have realized a new approach to produce highly stochastic light pulses; i.e. dominated by frequency uncorrelated intensity fluctuation.

Final results

The research carried out within INCEPT up to now, served the purpose to set the bases (both theoretical and experimental) for harnessing statistical properties of light for non-equilibrium spectroscopies. The overall scope of INCEPT is to understand to what extent we can use quantum and classical fluctuation of light to address inhomogeneities and fluctuations in complex materials. The research in the next years will be dedicated to exploiting such bases and, thereby, seed the nascent research of quantum spectroscopies in complex materials.
In detail, the progress made up to now is highlighted in the 3 major publications reported. In Physical Review Letters 119, 187403 (2017) we showed that transient photon noise spectroscopy allows us to measure to what extent electronic degrees of freedom dynamically obey the fluctuation-dissipation theorem, and how well they thermalize during the coherent lattice vibrations. In https://arxiv.org/abs/1811.01861 we have shown that noise in a femtosecond laser is not necessarily a liability to be mitigated, but femotosecond covariance spectroscopy can act as a unique and powerful asset capable of retrieving the Raman response of the material. Finally, in https://arxiv.org/abs/1810.11399 we have developed a fully quantum model for describing the interaction between ultrashort light pulses and the elastic field of materials which will allow us to have an effective description on how light-matter interaction can result in multimode correlations at the quantum level.