We introduce a method for the conditional generation of nonclassical states of light in a cavity. We consider two-level atoms traveling along the transverse direction to the cavity axis and show that by conditioning on one of the output measurements nonclassical field states are generated. The two-level atoms are prepared in the ground state and we conditioned on the events in which they are also detected in the ground state. Nonclassical properties of the cavity mode are identified and characterized. This includes: quadrature squeezing, sub-Poissonian photon-number distributions, and negative Wigner functions. We determine the optimal parameter regions where the corresponding nonclassical features are most distinct. * elizabeth.agudelo@oeaw.ac.at † martin.bohmann@ino.it [22][23][24][25], squeezed states [26], or superposition states such as Schrödinger-cat state [27,28].

No abstract

Regular inspections of underground infrastructure are mandatory to maintain structural integrity and traffic safety. Standard procedures rely on visual inspection, complemented by testing for internal defects of the tunnel lining with the hammering method. This testing method uses manual excitation with a hammer and interpretation of the perceived sound by an engineer or technician. Result quality is based on the experience of the executing personal and thus highly subjective. The presented project aims at the automation of this procedure to enable a fast and objective inspection covering the whole tunnel lining. To achieve this, a new laser-based measurement system for detecting near surface defects in large concrete structures is developed. Surface vibrations are induced with plasma ignition and measured with a Doppler Vibrometer. The system has motorized mirror adjustment and can thus obtain fast-paced measurements on a grid. We present the experimental setup, the measurements performed on a concrete test block with artificial defects and the algorithms for automated defect detection. From the measured eigenfrequencies, we derive the size and location of defects. Computer vision techniques are adapted to make the system resilient against variable environmental conditions, like noise and temperature, or changes in construction material and age. These sophisticated signal processing methods are applied to extract relevant information from the measurements and are combined with topological data to provide service personnel with detailed maps for maintenance work.

Tunnel inspections require the detection of deformations in the tunnel geometry, cracks, delamination, and water inflow. Solutions for an automated detection of deformations, cracks and water inflow already exist and typically comprise mobile laser-scanners and cameras combined with deep learning methods. Delaminations on the other hand are often not visible on the surface and can't be detected using these methods. The detection of delamination in tunnel linings is therefore up to date performed by manual hammering and acoustic detection. The results are time consuming and labor-intensive inspections, subjective measurements, poor comparisons over epochs and a low degree of digitization. We present a concept of a novel system that aims to replace the manual hammering for acoustic delamination detection using a remote sensing approach. A strong, pulsed laser serves as a hammer and creates a plasma induced shockwave on the concrete surface. If a delamination is present this shockwave excites characteristic, resonant vibrations. A second, narrow-linewidth laser is employed in a customized laser doppler vibrometer setup to remotely detect these vibrations via a coherent measurement technique. In combination with laser scanners and cameras, the laser based remote sensing technique has the potential to help automating the process of tunnel inspections by delivering objective data that can be used in deep learningbased evaluation methods and for building information modeling (BIM) compliant assessment. A first mobile prototype for measurements outside the lab has been developed and is being presented in detail.