Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities

Key to future spintronics and spin-based information processing technologies is the generation, manipulation, and detection of spin polarization in a solid state platform. Here, we theoretically explore an alternative route to spin injection via the use of dynamically polarized nitrogen-vacancy (NV) centers in diamond. We focus on the geometry where carriers and NV centers are confined to proximate, parallel layers and use a 'trap-and-release' model to calculate the spin cross-relaxation probabilities between the charge carriers and neighboring NV centers. We identify near-unity regimes of carrier polarization depending on the NV spin state, applied magnetic field, and carrier g-factor. In particular, we find that unlike holes, electron spins are distinctively robust against spin-lattice relaxation by other, unpolarized paramagnetic centers. Further, the polarization process is only weakly dependent on the carrier hopping dynamics, which makes this approach potentially applicable over a broad range of temperatures.C.A.M. acknowledges support from the National Science Foundation through Grant No. NSF-1314205. M.W.D. acknowledges support from the Australian Research Council through Grant No. DP120102232

A large family of quantum weak coin-flipping protocols

Each classical public-coin protocol for coin flipping is naturally associated with a quantum protocol for weak coin flipping. The quantum protocol is obtained by replacing classical randomness with quantum entanglement and by adding a cheat detection test in the last round that verifies the integrity of this entanglement. The set of such protocols defines a family which contains the protocol with bias 0.192 previously found by the author, as well as protocols with bias as low as 1/6 described herein. The family is analyzed by identifying a set of optimal protocols for every number of messages. In the end, tight lower bounds for the bias are obtained which prove that 1/6 is optimal for all protocols within the family.Comment: 17 pages, REVTeX 4 (minor corrections in v2

Strong experimental guarantees in ultrafast quantum random number generation

We describe a methodology and standard of proof for experimental claims of quantum random number generation (QRNG), analogous to well-established methods from precision measurement. For appropriately constructed physical implementations, lower bounds on the quantum contribution to the average min-entropy can be derived from measurements on the QRNG output. Given these bounds, randomness extractors allow generation of nearly perfect "{\epsilon}-random" bit streams. An analysis of experimental uncertainties then gives experimentally derived confidence levels on the {\epsilon} randomness of these sequences. We demonstrate the methodology by application to phase-diffusion QRNG, driven by spontaneous emission as a trusted randomness source. All other factors, including classical phase noise, amplitude fluctuations, digitization errors and correlations due to finite detection bandwidth, are treated with paranoid caution, i.e., assuming the worst possible behaviors consistent with observations. A data-constrained numerical optimization of the distribution of untrusted parameters is used to lower bound the average min-entropy. Under this paranoid analysis, the QRNG remains efficient, generating at least 2.3 quantum random bits per symbol with 8-bit digitization and at least 0.83 quantum random bits per symbol with binary digitization, at a confidence level of 0.99993. The result demonstrates ultrafast QRNG with strong experimental guarantees.Comment: 11 pages, 9 figure

Implementation of a point-of-care ultrasound skills practicum for hospitalists

Introduction Point-of-care ultrasound is recognized as a safe and valuable diagnostic tool for patient evaluation. Hospitalists are prime candidates for advancing the point-of-care ultrasound field given their crucial role in inpatient medicine. Despite this, there is a notable lack of evidence-based ultrasound training for hospitalists. Most research focuses on diagnostic accuracy rather than the training required to achieve it. This study aims to improve hospitalists' point-of-care ultrasound knowledge and skills through a hands-on skills practicum. Methods Four skill practicums were conducted with pre-course, post-course, and six-month evaluations and knowledge assessments. Results The mean pre- vs. post-course knowledge assessment scores significantly improved, 41.7% vs. 75.9% (SD 16.1% and 12.7%, respectively, p < 0.0001). The mean ultrasound skills confidence ratings on a 10-point Likert scale significantly increased post-course (2.60 ± 1.66 vs. 6.33 ± 1.63, p < 0.0001), but decreased at six months (6.33 ± 1.63 vs. 4.10 ± 2.22, p < 0.0001). The greatest limitations to usage pre-course and at six months were knowledge/skills and lack of machine access. While knowledge/skills decreased from pre-course (82.0%) as compared to six-months (64.3%), lack of machine access increased from pre-course (15.8%) to six-months (28.6%) (p = 0.28). Conclusion Hospitalists agree that point-of-care ultrasound has utility in the diagnostic and therapeutic management of patients, though the lack of training is a significant limitation. Our study demonstrated that a brief skills practicum significantly improves hospitalists’ confidence and knowledge regarding ultrasound image acquisition and interpretation in the short term. Long-term confidence and usage wanes, which appears to be due to the lack of machine access

PepMat 2016: The second conference on peptide-based materials for biomedicine and nanotechnology

Postprint (published version