Organic molecule fluorescence as an experimental test-bed for quantum jumps in thermodynamics

Single-molecule fluorescence spectroscopy is a powerful method that avoids ensemble averaging, but its temporal resolution is limited by the fluorescence lifetime to nanoseconds at most. At the ensemble level, two-dimensional spectroscopy provides insight into ultrafast femtosecond processes such as energy transfer and line broadening, even beyond the Fourier limit, by correlating pump and probe spectra. Here, we combine these two techniques and demonstrate 2D spectroscopy of...

Quantum mechanical phenomena, such as electronic coherence and entanglement, play a key role in achieving the unrivalled efficiencies of light-energy conversion in natural photosynthetic light-harvesting complexes, and triggered the growing interest in the possibility of organic quantum computing. Since biological systems are intrinsically heterogeneous, clear relations between structural and quantum-mechanical properties can only be obtained by investigating individual assem...

The local interaction of charges and light in organic solids is the basis of distinct and fundamental effects. We here observe, at the single molecule scale, how a focused laser beam can locally shift by hundreds-time their natural linewidth and in a persistent way the transition frequency of organic chromophores, cooled at liquid helium temperatures in different host matrices. Supported by quantum chemistry calculations, the results are interpreted as effects of a photo-ioni...

We present a method for determining the free energy of coexisting states from irreversible work measurements. Our approach is based on a fluctuation relation that is valid for dissipative transformations in partially equilibrated systems. To illustrate the validity and usefulness of the approach, we use optical tweezers to determine the free energy branches of the native and unfolded states of a two-state molecule as a function of the pulling control parameter. We determine, ...

Organic molecules have recently gained attention as novel sources of single photons. We present a joint experiment--theory analysis of the temperature-dependent emission spectra, zero-phonon linewidth, and second-order correlation function of light emitted from a single molecule. We observe spectra with a zero-phonon-line together with several additional sharp peaks, broad phonon sidebands, and a strongly temperature dependent homogeneous broadening. Our model includes both l...

The evolution of molecular quantum states is central to many research areas, including chemical reaction dynamics, precision measurement, and molecule based quantum technology. Details of the evolution is often obscured, however, when measurements are performed on an ensemble of molecules, or when the molecules are subjected to environmental perturbations. Here, we report real-time observations of quantum jumps between rotational states of a single molecule driven by thermal ...

In this paper, single-molecule spectroscopy experiments based on continuous laser excitation are characterized through an open quantum system approach. The evolution of the fluorophore system follows from an effective Hamiltonian microscopic dynamic where its characteristic parameters, i.e., its electric dipole, transition frequency, and Rabi frequency, as well as the quantization of the background electromagnetic field and their mutual interaction, are defined in an extended...

The Jarzynski Equality relates the free energy difference between two equilibrium states of a system to the average of the work over all irreversible paths to go from one state to the other. We claim that the derivation of this equality is flawed, introducing an ad hoc and unjustified weighting factor which handles improperly the heat exchange with a heat bath. Therefore Liphardt et al's experiment cannot be viewed as a confirmation of this equality, although the numerical de...

Most natural and engineered processes, such as biomolecular reactions, protein folding, and population dynamics, occur far from equilibrium and, therefore, cannot be treated within the framework of classical equilibrium thermodynamics. The Jarzynski equality holds the promise to calculate the free-energy difference between two states from the Boltzmann-weighted statistics of the irreversible work done along trajectories arbitrarily out of equilibrium. This equality is the sub...

Using the principles of the ETH - Approach to Quantum Mechanics we study fluorescence and the phenomenon of ``quantum jumps'' in idealized models of atoms coupled to the quantized electromagnetic field. In a limiting regime where the orbital motion of the atoms is neglected and the velocity of light tends to infinity we derive explicit non-linear stochastic differential equations describing the effective time evolution of states of individual atoms. These equations give rise ...