COMPARING DISTRIBUTED ACOUSTIC SENSING TO THREE-COMPONENT GEOPHONES IN AN UNDERGROUND MINE

Geophones have become the industry standard for seismic data collection. However, a relatively new method is gaining popularity called Distributed Acoustic Sensing (DAS). DAS uses changes in backscattered light of a fiber-optic cable to detect strain from acoustic energy. The purpose of this project was to make a direct comparison between DAS and three component geophones, specifically in a mining setting. Experiments were done in the Underground Education Mining Center on the campus of Montana Tech. The sources used for this project were vertical sledgehammer shots, oriented shear sledgehammer shots, and blasting caps set off in both unstemmed and stemmed drillholes. Although the explosives performed the best for the geophones, the large amount of energy and its close distance from the fiber seemed to compromise the entire fiber loop. In a one to one comparison, the underground hammer shots seemed to produce data that was a rough match between the DAS traces and the geophone traces. However, the shots on the surface of the mine, specifically the shots oriented inline with the cable, seemed be close to an exact match between trace of the fiber and traces of the geophones. The data suggest that DAS is most useful when the fiber can be oriented in the same direction as particle motion from whatever source is used, whereas the three component geophones can accurately capture data from all sources

Back-Action Evading Measurement in Gravitational Wave Detectors to Overcome Standard Quantum Limit, Using Negative Radiation Pressure

Aiming at application for gravitational wave (GW) detection, we propose a novel scheme how to obtain quantum back action evading measurements performed on an opto-mechanical cavity, by introducing a negative radiation pressure coupling between the cavity field and the end mirror. The scheme consists of introducing a double cavity with end mirrors interlocked by a pivot and moving in opposite directions. The measurement is performed by sending a two-mode squeezed vacuum to both cavities and detecting the output through the heterodyne detection. Compared to the previously proposed hybrid negative mass spin-optomechanical system in Phys. Rev. Lett. 121, 031101 (2018), we see that our scheme is capable to suppress back action noise by nearly two orders of magnitude more in the lower frequency region. Overall, the setup has been able to squeeze the output noise below the standard quantum limit, with more efficiency. In addition, the scheme has also proven to be beneficial for reducing thermal noise by a significant amount. We confirm our result by a numerical analysis and compared it with the previous proposal Phys. Rev. Lett. 121, 031101 (2018).Comment: 5 pages, 2 figure

Optical quenching and recovery of photoconductivity in single-crystal diamond

We study the photocurrent induced by pulsed-light illumination (pulse duration is several nanoseconds) of single-crystal diamond containing nitrogen impurities. Application of additional continuous-wave light of the same wavelength quenches pulsed photocurrent. Characterization of the optically quenched photocurrent and its recovery is important for the development of diamond based electronics and sensing

Room-temperature control and electrical readout of individual nitrogen-vacancy nuclear spins

Nuclear spins in semiconductors are leading candidates for quantum technologies, including quantum computation, communication, and sensing. Nuclear spins in diamond are particularly attractive due to their extremely long coherence lifetime. With the nitrogen-vacancy (NV) centre, such nuclear qubits benefit from an auxiliary electronic qubit, which has enabled entanglement mediated by photonic links. The transport of quantum information by the electron itself, via controlled transfer to an adjacent centre or via the dipolar interaction, would enable even faster and smaller processors, but optical readout of arrays of such nodes presents daunting challenges due to the required sub-diffraction inter-site distances. Here, we demonstrate the electrical readout of a basic unit of such systems - a single 14N nuclear spin coupled to the NV electron. Our results provide the key ingredients for quantum gate operations and electrical readout of nuclear qubit registers, in a manner compatible with nanoscale electrode structures. This demonstration is therefore a milestone towards large-scale diamond quantum devices with semiconductor scalability.Comment: 11 pages, 4 figure