Quantum Optical Efects In The Nanomechanical Systems And Their Application In Mass Sensing

There is widespread technological and scientifc interest in namome-chanical systems for their applications in diverse felds ranging from quan-tum measurement to biotechnology due to their sensitivity to external in-fuences. This inherent sensitivity makes nanomechanical resonator (NR)functions as an ultrasensitive transducer. At this early stage of develop-ment, doubly clamped beams have been found to use as mass sensitivetransducers. What’s more, the cantilevers designed for atomic force mi-croscopy also have been applied as mass sensors later. Recently, the feldof cavity quantum electrodynamics (cQED) has emerged as one of theburgeoning domains of physics. In analogy with optomechanical system-s, coherent coupling via mechanical phonons is a promising approach toprepare and manipulate quantum states of mechanical oscillators. The-oretical studies clearly point out the possibility of coherent interactionbetween the localized two-level exciton and the nanomechanical systems,which makes it possible to create coherent superpositions of quantum s-tates of the localized two-level exciton and the mechanical resonator. Inthe presence of a strong pump feld and a weak probe feld, the couplingof localized two-level exciton to vibrational motion of nanomechanical res-onator is analogous with the coupling of cavity to mechanical oscillator in optomechanical system, where the role of the optical cavity is playedby an localized two-level exciton, while the role of the mechanical ele-ment is replaced by the nanomechanical resonator’s vibration. Inspiredby cQED and compared to the frequency detection based on the elec-trical techniques, we propose the following:(1) In combination with thepump-probe techniques, we theoretically propose a scheme to measure theresonator frequency and coupling strength in a hybrid spin-mechanical res-onator system which has a strong coherent coupling of a electronic spin ofa single nitrogen vacancy (NV) center in diamond with a nanomechanicalresonator;(2) We theoretically study the measurement of molecular massusing a hybrid spin-mechanical systems as a detector;(3) Based on the all-optical technique, we propose a scheme of an optical mass sensor to weighthe mass of a single atom or molecule via a doubly clamped Z-shapedgraphene nanoribbon (GNR). This paper consists of fve chapters.In Chapter One, we introduce the basic theories and developmenthistory of nanomechanical system. Then we give a brief introduction tothe excellent feature of nanomechanical system. we also give some specialemphasis on its application in various felds. We detail how the atomicforce microscope works and the mass sensing principle of nanomechanicalresonator.In Chapter Two, we propose a scheme to measure the vibrational fre-quency of nanome-chanical resonator and the coupling strength betweenan electronic spin qubit and a nanome-chanical resonator in a hybridspin-mechanical resonator system due to mechanically induced coherentpopulation oscillation. It is shown that, for a given pump detuning, thevibrational frequency of the nanomechanical resonator can be obtainedin the probe absorption spec-trum. Additionally, one can easily measurethe coupling strength with the distance of two peaks in the probe ab- sorption spectrum when the pump detuning matches the frequency of thenanomechanical resonator. The proposed technique will ofer potential ap-plications in spin-based hybrid quantum-computing system and quantuminformation processing.In Chapter Three, we theoretically put forward a mass sensor basedon spin-NR-mass system. The accreted mass landing on the distal endof a clamped-free nanomechanical resonator can be measured convenient-ly and precisely according to the frequency shift in the probe absorptionspectrum. Most notably, due to the consideration of the landing positionefect of particles, we propose a more accurate resonator mechanism inmass sensor. According to the all-microwave measurement, the spin-NRmass sensing scheme proposed here has signifcant advantage over the tra-ditional electrical approaches for measuring the inertial mass of particlesand organic molecules.In Chapter Four, we theoretically propose an optical mass sensorbased on the Z-shaped GNR. The accreted mass landing on the Z-shapedGNR resonator can be measured conveniently and precisely according tothe frequency shift in the probe absorption spectrum. Most notably, due toits ultrasmall mass and higher quality factor, the GNR-based mass sensormay apply to detect single nucleonic mass in all-optical domains and havethe potential to ofer a direct method for the identifcation of chemicalelements. Finally, we hope that our propose d device can be realized byexperiments in the near future.In Chapter Five, it is the summary and prospects.