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INhomogenieties and fluctuations in quantum CohErent matter Phases by ultrafast optical Tomography

Periodic Reporting for period 4 - INCEPT (INhomogenieties and fluctuations in quantum CohErent matter Phases by ultrafast optical Tomography)

Okres sprawozdawczy: 2020-12-01 do 2022-11-30

The goal of INCEPT project was to develop a new generation of time resolved spectroscopy combining quantum optic techniques with the traditional pump and probe approach, and thereby set the fundaments to use statistical properties of light in non-equilibrium spectroscopy. The leitmotiv of the action was the fact that light-matter interaction can imprint in the quantum state of probe pulses information on the transient response of the material which are not visible in mean value probe properties but can be retrieved by studying the full statistical properties of light. To this purpose, in INCEPT we implemented a combined theoretical and experimental action and delivered both the hardware to measure photonic fluctuation in time domain experiments, as well as the theoretical framework to understand which is the information carried by such fluctuations.

In contrast to standard optical techniques, which measure the probe pules after the interaction with the sample integrated over many repetitions, we developed different single shot detection schemes which allow for the measurements of the photon number fluctuations in probe pulses both frequency integrated and frequency-resolved. We implemented and used experiments combining non-equilibrium spectroscopy techniques and statistical characterization of the probe pulses. We developed means to exploit both classical fluctuations of laser pulses as well as the intrinsic fluctuations of quantum origin. In addition to the experimental development we have developed an effective theoretical framework to understand how fluctuations in materials are mapped onto measurable photonic fluctuations of probe properties.

INCEPT activities have been well timed with other efforts in the scientific community. 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 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 is testified by the high profile of our publications and a large number of invited contributions to the major conferences the team members received. Thanks also to INCEPT activities the non-equilibrium community is now recognizing the potential of combining non-equilibrium approaches with quantum information protocols for understanding and controlling the functionalities of complex quantum materials. Overall, the action has been successful and delivered the scientific fundaments of a possible new paradigm for non-equilibrium spectroscopies leveraging on photonic noise.
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 intensity fluctuation (both classical and quantum) in time domain experiment.

Using classical multimode intensity fluctuations, we established femtosecond covariance spectroscopy, a technique that uses ultrashort stochastic light pulses to measure nonlinear material responses. We developed pulse shaping techniques to introduce in ultrashort pulses spectrally uncorrelated fluctuations. In this condition, each repetition of the experiment can be considered as a measurement performed under different conditions and nonlinear processes in the samples can be retrieved by measuring the spectral correlations in different repetition of the experiments. We validate the Femtosecond Covariance Based approach by studying coherent phonon responses in by near-IR pump and probe by Impulsively Stimulated Raman Scattering (ISRS).

We developed a pump&probe (p&p) setup capable of measuring photon number fluctuation and performing multimode quantum state probe measurements. In particular, we combined p&p with single shot multichannel detectors and pulse shaping capabilities to perform femtosecond time- and frequency-resolved multimode heterodyne detection. This unique experimental characterization of the field quadratures, reveals that their amplitude and phase encode different information and enables the independent measurement of the time evolution of the position and momentum of the atoms in coherent vibrational states. In parallel to the experimental activities, we developed a theoretical framework which treats effectively the interaction between photonic and photonic degrees of freedom in time domain experiment.

The success of the project can be deduced by the scientific output of Fausti’s group in the INCEPT years. The research carried out in INCEPT resulted in 16 publication (11 led by the PI). The publication include 6 manuscript on high impact factor journal (>9).
The results were presented as invited contribution at more than 20 workshops and conferences.

The methodology developed in INCEPT of femtosecond covariance baser Raman spectroscopy is potentially a disruptive methodology for the Raman spectroscopy. In order to make the technique efficient and versatile as currently available Raman platform we have proposed and carried out a Proof Of Concept (PoC) program where we developed fast detector and tested the general applicability of Covariance base Raman spectroscopy.
The research carried out within INCEPT set the bases (both theoretical and experimental) for harnessing statistical properties of light for non-equilibrium spectroscopies. The scope overarching INCEPT’s activities was to understand to what extent we can use quantum and classical fluctuation of light to address inhomogeneities and fluctuations in complex materials.

The main results of INCEPT is the experimental demonstration that photonic noise in time domain spectroscopies carry a wealth of information which are lost in mean value measurements and the development of a theoretical framework to unveil the physical significance of such information. We developed p&p experiments providing the means to measure photon number fluctuations, integrated over the spectral bandwidth and frequency resolved, in the classical and quantum regime.

Making use of the framework developed we have shown that time domain spectroscopies based on photonic noise enable the retrieval of information beyond linear and non-linear optics. We have devised means to unveil the vibrational characteristic of a material with a time resolution higher than the phonon period by mapping amplitude and phase of time dependent vibrational states. We revealed a path to identify spectral fingerprints of fluctuations of the atomic position in non-equilibrium context and applied single shot techniques to study fluctuations in high temperature superconductors obtaining encouraging results which will be exploited in the yeas to come. Overall, the overarching goal of INCEPT of setting the path to a full exploitation of photonic noise in non linear spectroscopy has been fully achieved.
Ft module
Pump probe
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