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Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting. We insert a sample in the Hong-Ou-Mandel interferometer and observe the modification of the two-photon interference pattern, which is driven by the coherent response of the medium, determined by the dephasing time. The dephasing time is then inferred from the observed pattern. This effect is distinctively different from the basic effect of spectral filtering, which was studied in earlier works. In addition to its ease of use, our technique does not require compensation of group velocity dispersion and does not induce photo-damage of the samples. Our technique will be useful for characterization of ultrafast phase relaxation processes in material science, chemistry, and biology.
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http://dx.doi.org/10.1038/s41598-017-11694-z | DOI Listing |
Phys Rev Lett
August 2025
Cavendish Laboratory, NanoPhotonics Centre, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge CB3 0US, United Kingdom.
Coupling with a resonant optical cavity is well known to modify the coherence of molecular vibrations. However, in the case of molecules coupled to a plasmonic nanocavity mode, the local mechanisms of vibrational coherence decay remain unclear. Here, the dynamics of a few hundred molecules of nitrothiophenol (NTP) within a single plasmonic nanocavity are studied by sum-frequency generation.
View Article and Find Full Text PDFJ Chem Phys
September 2025
Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
We introduce an efficient method, TTN-HEOM, for exactly calculating the open quantum dynamics for driven quantum systems interacting with highly structured bosonic baths by combining the tree tensor network (TTN) decomposition scheme with the bexcitonic generalization of the numerically exact hierarchical equations of motion (HEOM). The method yields a series of quantum master equations for all core tensors in the TTN that efficiently and accurately capture the open quantum dynamics for non-Markovian environments to all orders in the system-bath interaction. These master equations are constructed based on the time-dependent Dirac-Frenkel variational principle, which isolates the optimal dynamics for the core tensors given the TTN ansatz.
View Article and Find Full Text PDFJ Phys Chem Lett
September 2025
Institute of Polymer Optoelectronic Materials and Devices, Guangdong Basic Research Center of Excellence for Energy & Information Polymer Materials, Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, State Key Laboratory of Luminescent Materials and Devic
Organic luminescent diradicals have recently attracted more attention for their potential applications in quantum science. Here, we have investigated the spin dynamic properties of two solid-state Müller- and Chichibabin-type Kekulé diradicals featuring different distances between two radical centers. The continuous-wave EPR (cw-EPR) together with echo-detected field-swept spectrum (EDFS) prove the existence of a thermally accessible triplet state at room temperature, promising a potential candidate for quantum manipulation as a high-spin state.
View Article and Find Full Text PDFAdv Sci (Weinh)
August 2025
Nano-Optics and Biophotonics Group, Experimentelle Physik 5, Physikalisches Institut, Universität Würzburg, D-97074, Würzburg, Germany.
Strong coupling between a single quantum emitter and a resonant plasmonic mode at room temperature is vital for quantum information processing and sensing. Beating dephasing in these systems by ultrafast energy transfer requires coupling single emitters to a plasmonic nanoresonator with ultrasmall mode volume and optimal spectral overlap. Typically, strong coupling is inferred from normal mode splittings in luminescence spectra, offering rough estimates of coupling strength.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
Universität Bonn, Physikalisches Institut, Nussallee 12, 53115, Bonn, Germany.
We study the temporal, driven-dissipative dynamics of open photon Bose-Einstein condensates (BEC) in a dye-filled microcavity, taking the condensate amplitude and the noncondensed fluctuations into account on the same footing by means of a cumulant expansion within the Lindblad formalism. The fluctuations fundamentally alter the dynamics in that the BEC always dephases to zero for a sufficiently long time. However, a ghost attractor, although outside of the physically accessible configuration space, attracts the dynamics and leads to a plateaulike stabilization of the BEC for an exponentially long time, consistent with experiments.
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