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

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

OSCAR-QUBE: student made diamond based quantum magnetic field sensor for space applications

Project OSCAR-QUBE (Optical Sensors Based on CARbon materials - QUantum BElgium) is a project from Hasselt University and research institute IMO-IMOMEC that brings together the fields of quantum physics and space exploration. To reach this goal, an interdisciplinary team of physics, electronics engineering and software engineering students created a quantum magnetometer based on nitrogen-vacancy (NV) centers in diamond in the framework of the Orbit-Your-Thesis! programme from ESA Education. In a single year, our team experienced the full lifecycle of a real space experiment from concept and design, to development and testing, to the launch and commissioning onboard the ISS. The resulting sensor is fully functional, with a resolution of < 300 nT/ sqrt(Hz), and has been gathering data in Low Earth Orbit for over six months at this point. From this data, maps of Earth’s magnetic field have been generated and show resemblance to onboard reference data. Currently, both the NV and reference sensor measure a different magnetic field than the one predicted by the International Geomagnetic Reference Field. The reason for this discrepancy is still under investigation. Besides the technological goal of developing a quantum sensor for space magnetometry with a high sensitivity and a wide dynamic range, and the scientific goal of characterizing the magnetic field of the Earth, OSCAR-QUBE also drives student growth. Several of our team members are now (aspiring) ESA Young Graduate Trainees or PhD students in quantum research, and all of us took part in the team competition of the International Astronautical Congress in October 2021, where we won the Hans Von Muldau award. Being an interdisciplinary team, we brought many different skills and viewpoints together, inspiring innovative ideas. However, this could only be done because of our efforts to keep up a good communication and team spirit. We believe that if motivated people work hard to improve the technology, we can change the way magnetometry is done in space

Pulsed Photoelectric Coherent Manipulation and Detection of N − V Center Spins in Diamond

Hybrid photoelectric detection of NV magnetic resonances (PDMR) is anticipated to lead to scalable quantum chip technology. To achieve this goal, it is crucial to prove that PDMR readout is compatible with the coherent spin control. Here we present PDMR MW pulse protocols that filter background currents related to ionization of NS0 defects and achieve a high contrast and S/N ratio. We demonstrate Rabi and Ramsey protocols on shallow nitrogen-implanted electronic grade diamond and the coherent readout of ~ 5 NV spins, as a first step towards the fabrication of scalable photoelectric quantum devices

Physics and applications of CVD diamond

Here, leading scientists report on why and how diamond can be optimized for applications in bioelectronic and electronics. They cover such topics as growth techniques, new and conventional doping mechanisms, superconductivity in diamond, and excitonic properties, while application aspects include quantum electronics at room temperature, biosensors as well as diamond nanocantilevers and SAWs.Written in a review style to make the topic accessible for a wider community of scientists working in interdisciplinary fields with backgrounds in physics, chemistry, biology and engineering, this is