We report on the observation of Anderson wave localization in one-dimensional waveguide arrays with off-diagonal disorder. The waveguide elements are inscribed in silica glass, and a uniform random distribution of coupling parameters is achieved by a precise variation of the relative waveguide positions. In the absence of disorder we observe ballistic transport as expected from discrete diffraction in periodic arrays. When off-diagonal disorder is deliberately introduced into the array we observe Anderson localization. The strength of the localization signature increases with higher levels of disorder.

A minimal observable length is a common feature of theories that aim to merge quantum physics and gravity. Quantum mechanically, this concept is associated with a nonzero minimal uncertainty in position measurements, which is encoded in deformed commutation relations. In spite of increasing theoretical interest, the subject suffers from the complete lack of dedicated experiments and bounds to the deformation parameters have just been extrapolated from indirect measurements. As recently proposed, low-energy mechanical oscillators could allow to reveal the effect of a modified commutator. Here we analyze the free evolution of high-quality factor micro- and nano-oscillators, spanning a wide range of masses around the Planck mass m_P (≈22 μg). The direct check against a model of deformed dynamics substantially lowers the previous limits on the parameters quantifying the commutator deformation.

We propose a scheme for the generation of a robust stationary squeezed state of a mechanical resonator in a quadratically coupled optomechanical system, driven by a pulsed laser. The intracavity photon number presents periodic intense peaks suddenly stiffening the effective harmonic potential felt by the mechanical resonator. These “optical spring kicks” tend to squeeze the resonator position, and due to the interplay with fluctuation-dissipation processes one can generate a stationary state with more than 10 dB of squeezing in a realistic scenario, even starting from moderately “precooled” initial thermal states.

The active microcavity is adopted as an efficient source of nonclassical light. Using this device, excited with a mode-locked laser at a rate of 100 MHz, single photons are generated over a single field mode with a nonclassical sub-Poissonian distribution. Adiabatic recycling within a multistep Franck-Condon molecular optical-pumping mechanism, characterized by quantum efficiency close to 1, implies a pump self-regularization process leading to a striking $n$-squeezing effect. Replicating the basic single-atom excitation process a beam of quantum photon $|n〉$ states (Fock states) can be created. This represents a significant advance in the fields of basic quantum-mechanical investigation, quantum communication, and quantum cryptography.