411 research outputs found

    Cherri and Lisa Go to India

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    We spent 30 difficult days in the beautiful but impoverished country of India. Prior to the trip we made a small attempt to acquaint ourselves with the Indian culture and prepare for the shock of visiting a third-world country. Neither of us had traveled overseas before. We came to the conclusion (after the first day) that this was something that had to be experienced to comprehend, and reading a few books, watching documentaries on the Discovery Channel, or listening to others speak of their experiences while visiting the country did not do the job. Knowing a second language is always a plus while traveling, and we tried to learn a few phrases in Hindi (what we thought to be the national language) but discovered that each state had its own language. Impressively, many people were fluent in English and we always found someone to communicate with

    Wide-field strain imaging with preferentially aligned nitrogen-vacancy centers in polycrystalline diamond

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    We report on wide-field optically detected magnetic resonance imaging of nitrogen-vacancy centers (NVs) in type IIa polycrystalline diamond. These studies reveal a heterogeneous crystalline environment that produces a varied density of NV centers, including preferential orientation within some individual crystal grains, but preserves long spin coherence times. Using the native NVs as nanoscale sensors, we introduce a three-dimensional strain imaging technique with high sensitivity (<10⁻⁵Hz⁻½) and diffraction-limited resolution across a wide field of view.United States. Office of Naval Research (N00014-13-1-0316)United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative I(FA9550-14-1-0052)United States. Air Force Office of Scientific Research (Presidential Early Career Award

    Low-control and robust quantum refrigerator and applications with electronic spins in diamond

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    We propose a general protocol for low-control refrigeration and thermometry of thermal qubits, which can be implemented using electronic spins in diamond. The refrigeration is implemented by a probe, consisting of a network of interacting spins. The protocol involves two operations: (i) free evolution of the probe; and (ii) a swap gate between one spin in the probe and the thermal qubit we wish to cool. We show that if the initial state of the probe falls within a suitable range, and the free evolution of the probe is both unital and conserves the excitation in the zz-direction, then the cooling protocol will always succeed, with an efficiency that depends on the rate of spin dephasing and the swap gate fidelity. Furthermore, measuring the probe after it has cooled many qubits provides an estimate of their temperature. We provide a specific example where the probe is a Heisenberg spin chain, and suggest a physical implementation using electronic spins in diamond. Here the probe is constituted of nitrogen vacancy (NV) centers, while the thermal qubits are dark spins. By using a novel pulse sequence, a chain of NV centers can be made to evolve according to a Heisenberg Hamiltonian. This proposal allows for a range of applications, such as NV-based nuclear magnetic resonance of photosensitive molecules kept in a dark spot on a sample, and it opens up possibilities for the study of quantum thermodynamics, environment-assisted sensing, and many-body physics

    Wide-field Magnetic Field and Temperature Imaging using Nanoscale Quantum Sensors

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    The simultaneous imaging of magnetic fields and temperature (MT) is important in a range of applications, including studies of carrier transport, solid-state material dynamics, and semiconductor device characterization. Techniques exist for separately measuring temperature (e.g., infrared (IR) microscopy, micro-Raman spectroscopy, and thermo-reflectance microscopy) and magnetic fields (e.g., scanning probe magnetic force microscopy and superconducting quantum interference devices). However, these techniques cannot measure magnetic fields and temperature simultaneously. Here, we use the exceptional temperature and magnetic field sensitivity of nitrogen vacancy (NV) spins in conformally-coated nanodiamonds to realize simultaneous wide-field MT imaging. Our "quantum conformally-attached thermo-magnetic" (Q-CAT) imaging enables (i) wide-field, high-frame-rate imaging (100 - 1000 Hz); (ii) high sensitivity; and (iii) compatibility with standard microscopes. We apply this technique to study the industrially important problem of characterizing multifinger gallium nitride high-electron-mobility transistors (GaN HEMTs). We spatially and temporally resolve the electric current distribution and resulting temperature rise, elucidating functional device behavior at the microscopic level. The general applicability of Q-CAT imaging serves as an important tool for understanding complex MT phenomena in material science, device physics, and related fields
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