Improvements in fabrication and measurement technology have spurred an intense interest in using ultrasensitive micro- and nanomechanical resonators to probe quantum states. Researchers now have the ability to study the quantum behavior of small mechanical structures, their coupling to single electron states, to spin states, to light, and to the larger environment around them. Sensors able to detect the tiny forces arising from single charges or spins allow the study of a wide class of problems in condensed matter physics. Improved understanding of these phenomena may lead to new high resolution nano- and atomic-scale imaging techniques. This proposal consists of three projects in this vein: the coupling of mechanical modes to mesoscopic transport, nano-scale magnetic resonance force microscopy, and the exploration of new materials for use in nanomechanical systems. The coupling of mechanical modes to mesoscopic transport (project A) represents an exciting new direction whose pursuit has a variety of possible implications. In recent years, technologies have emerged -- more or less independently -- to fabricate both nanomechanical oscillators and tunable single electron devices. As a result, mechanical oscillators can now be coupled to quantized states such as single charges or spins. Such coupled systems have implications not only for quantum measurement but also as a means for manipulating quantum states. We intend to couple resonators to a variety of mesoscopic few-electron devices such as quantum point contacts (QPCs), quantum dots (QDs), and Mach-Zehnder interferometers. From a practical perspective, such systems provide an avenue for designing sensitive detectors of mechanical displacement -- detectors which approach the quantum limit. Magnetic resonance force microscopy (MRFM) and its subsequent extension into the nanoscale (project B) combine the physics of magnetic resonance imaging (MRI) with the techniques of scanning probe microscopy. MRFM has now been used both to measure magnetic resonance from a single electron spin and for nuclear MRI with a spatial resolution better than 10 nm. We propose to use the technique to study a variety of nanoscale spin systems -- both nuclear and electronic -- especially systems, which cannot be addressed by conventional optical or magnetic resonance techniques. We also aim to implement improvements in speed and sensitivity that will enable both higher spatial resolution and possibly the ability to read-out single electron spin states in real time, a feat not yet accomplished by groups in the field. The exploration of new materials for use in nanomechanical systems (project C) is a vital research area for the improvement of future nanomechanical systems (NEMS). Currently, the vast majority of NEMS are made from single-crystal Si or Si-based materials such as SiN. Despite its many advantages, the use of Si has problems as well, including poor electronic and optical properties, the presence of a variety of defects, and apparent limitations in mechanical dissipation. We will investigate the physics behind these dissipation mechanisms including mechanical energy loss due to non-contact friction, paramagnetic impurities, and other contaminants. We will also explore the use of mechanical resonators made from a variety of carbon-based materials, GaAs, and nanowires. The main applicant, Prof. Dr. Martino Poggio, has recently been elected Argovia Professor in the Physics Department at the University of Basel. He is designing a new laboratory and will be starting in January 2009. He received his A.B. in physics from Harvard in 2000 and his Ph.D. from the University of California, Santa Barbara in 2005. He has a strong background in semiconductor spintronics and ultrafast optics, having worked for Prof. David Awschalom in graduate school. His expertise and interest in nanomechanics and ultrasensitive force microscopy come from 3 years of working with experts in the field at the IBM Almaden Research Center in San Jose, CA. There he worked as a post-doctoral researcher in Dr. Dan Rugar's lab on several projects including high sensitivity nuclear magnetic resonance force microscopy. As part of the Center for Probing the Nanoscale, a joint center between Stanford and IBM, he collaborated with Prof. David Goldhaber-Gordon on a project combining micromechanics with quantum transport. Together with colleagues in Basel and with his Swiss and international collaborators, Prof. Poggio's e ort will be of the highest caliber.