Single-photon spectroscopy of a single molecule

The advent of single molecule optics has had a profound impact in fields ranging from biophysics to material science, photophysics, and quantum optics. However, all existing room-temperature single molecule methods have been based on fluorescence detection of highly efficient emitters. Here we demonstrate that standard, modulation-free measurements known from conventional absorption spectrometers can indeed detect single molecules. We report on quantitative measurements of th...

Single photon sources (SPSs) based on quantum emitters hold promise in quantum radiometry as metrology standard for photon fluxes at the low light level. Ideally this requires control over the photon flux in a wide dynamic range, sub-Poissonian photon statistics and narrow-band emission spectrum. In this work, a monochromatic single-photon source based on an organic dye molecule is presented, whose photon flux is traceably measured to be adjustable between 144 000 and 1320 00...

Single molecule spectroscopy aims at unveiling often hidden but potentially very important contributions of single entities to a system's ensemble response. Albeit contributing tremendously to our ever growing understanding of molecular processes the fundamental question of temporal evolution, or change, has thus far been inaccessible, resulting in a static picture of a dynamic world. Here, we finally resolve this dilemma by performing the first ultrafast time-resolved transi...

A single quantum emitter can possess a very strong intrinsic nonlinearity, but its overall promise for nonlinear effects is hampered by the challenge of efficient coupling to incident photons. Common nonlinear optical materials, on the other hand, are easy to couple to but are bulky, imposing a severe limitation on the miniaturization of photonic systems. In this work, we show that a single organic molecule acts as an extremely efficient nonlinear optical element in the stron...

The efficient interaction of light with quantum emitters is crucial to most applications in nano and quantum photonics, such as sensing or quantum information processing. Effective excitation and photon extraction are particularly important for the weak signals emitted by a single atom or molecule. Recent works have introduced novel collection strategies, which demonstrate that large efficiencies can be achieved by either planar dielectric antennas combined with high numerica...

Nonlinear spectroscopy with quantum entangled photons is an emerging field of research that holds the promise to achieve a superior signal-to-noise ratio and effectively isolate many-body interactions. Photon sources used for this purpose however lack the frequency tunability and spectral bandwidth demanded by contemporary molecular materials. Here, we present design strategies for efficient spontaneous parametric downconversion to generate biphoton states with adequate spect...

The successful development of future photonic quantum technologies heavily depends on the possibility of realizing robust, reliable and, crucially, scalable nanophotonic devices. In integrated networks, quantum emitters can be deployed as single-photon sources or non-linear optical elements, provided their transition linewidth is broadened only by spontaneous emission. However, conventional fabrication approaches are hardly scalable, typically detrimental for the emitter cohe...

Quantum Key Distribution (QKD) allows the distribution of cryptographic keys between multiple users in an information-theoretic secure way, exploiting quantum physics. While current QKD systems are mainly based on attenuated laser pulses, deterministic single-photon sources could give concrete advantages in terms of secret key rate (SKR) and security owing to the negligible probability of multi-photon events. Here, we introduce and demonstrate a proof-of-concept QKD system ex...

The optomechanical character of molecules was discovered by Raman about one century ago. Today, molecules are promising contenders for high-performance quantum optomechanical platforms because their small size and large energy-level separations make them intrinsically robust against thermal agitations. Moreover, the precision and throughput of chemical synthesis can ensure a viable route to quantum technological applications. The challenge, however, is that the coupling of mo...

Single dye molecules at cryogenic temperatures display many spectroscopic phenomena known from free atoms and are thus promising candidates for fundamental quantum optical studies. However, the existing techniques for the detection of single molecules have either sacrificed the information on the coherence of the excited state or have been inefficient. Here we show that these problems can be addressed by focusing the excitation light near to the absorption cross section of a ...