Quantum physics meets biology.

Quantum physics and biology have long been regarded as unrelated disciplines, describing nature at the inanimate microlevel on the one hand and living species on the other hand. Over the past decades the life sciences have succeeded in providing ever more and refined explanations of macroscopic phenomena that were based on an improved understanding of molecular structures and mechanisms. Simultaneously, quantum physics, originally rooted in a world-view of quantum coherences, entanglement, and other nonclassical effects, has been heading toward systems of increasing complexity. The present perspective article shall serve as a "pedestrian guide" to the growing interconnections between the two fields. We recapitulate the generic and sometimes unintuitive characteristics of quantum physics and point to a number of applications in the life sciences. We discuss our criteria for a future "quantum biology," its current status, recent experimental progress, and also the restrictions that nature imposes on bold extrapolations of quantum theory to macroscopic phenomena

Raman bands of double-wall carbon nanotubes : comparison with single- and triple-wall carbon nanotubes, and influence of annealing and electron irradiation

We compare the G and G'2D bands of single-, double- and triple-wall carbon nanotubes (CNTs). We observe that the band shape is sensitive to the number of walls of the CNTs. For single-wall carbon nanotubes (SWCNTs), the G band is composed of two distinct contributions G+ and G−, while the G band for double-wall nanotubes is composed of one band with twomain contributions from the inner and the outer tube. The G'2D band can be fitted with one Lorentzian for single-wall tubes, while two distinct contributions are observed for double-wall carbon nanotubes (DWCNTs). Considerable variations of the G'2D band are found with similar first order Raman spectra. Annealing influences the D- and RBM-band intensities. Electron irradiation has the effect of decreasing the G- and D-band wavenumbers but does not enhance the D-band intensity considerably. The down-shifts of the G- and D-band wavenumbers are correlated and are the same for two excitation wavelengths. This is consistent with the scattering of phonons around the K-point

Programmable linear quantum networks with a multimode fibre

Reconfigurable quantum circuits are fundamental building blocks for the implementation of scalable quantum technologies. Their implementation has been pursued in linear optics through the engineering of sophisticated interferometers1–3. Although such optical networks have been successful in demonstrating the control of small-scale quantum circuits, scaling up to larger dimensions poses significant challenges4,5. Here, we demonstrate a potentially scalable route towards reconfigurable optical networks based on the use of a multimode fibre and advanced wavefront shaping techniques. We program networks involving spatial and polarization modes of the fibre and experimentally validate the accuracy and robustness of our approach using two-photon quantum states. In particular, we illustrate the reconfigurability of our platform by emulating a tunable coherent absorption experiment6. By demonstrating reliable reprogrammable linear transformations, with the prospect to scale, our results highlight the potential of complex media driven by wavefront shaping for quantum information processing

Real-time single-molecule imaging of quantum interference

The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter–wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the “most beautiful experiment in physics”. Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514 AMU and 1,298 AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave–particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics