193 research outputs found
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
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