Radio Astronomy

Contains research objectives and reports on one research project.National Aeronautics and Space Administration (Grant NsG-250-62)National Aeronautics and Space Administration (Grant NsG-419)Office of Naval Research (Contract Nonr-3963(02

Radio Astronomy

Contains research objectives and reports on two research projects.National Aeronautics and Space Administration (Grant NsG-250-62)National Aeronautics and Space Administration (Grant NsG-419)U. S. Navy (Office of Naval Research) under Contract Nonr-3963(02)-Task 2Lincoln Laboratory, Purchase Order DDL BB-107U. S. Air Force under Contract AF 19(628)-50

Conserved Charge Fluctuations from Lattice QCD and the Beam Energy Scan

We discuss the next-to-leading order Taylor expansion of ratios of cumulants of net-baryon number fluctuations. We focus on the relation between the skewness ratio, $S_B\sigma_B = \chi_3^B/\chi_1^B$, and the kurtosis ratio, $\kappa_B\sigma_B^2 =\chi_4^B/\chi_2^B$. We show that differences in these two cumulant ratios are small for small values of the baryon chemical potential. The next-to-leading order correction to $\kappa_B\sigma_B^2$ however is approximately three times larger than that for $S_B\sigma_B$. The former thus drops much more rapidly with increasing beam energy, $\sqrt{s_{NN}}$. We argue that these generic patterns are consistent with current data on cumulants of net-proton number fluctuations measured by the STAR Collaboration at $\sqrt{s_{NN}}\ge 19.6$~GeV.Comment: 4 pages, 4 figures, contribution to the Quark Matter 2015 proceeding

Radio Astronomy

Contains reports on four research projects.National Aeronautics and Space Administration (Grant NsG-264-62)U. S. Navy (Office of Naval Research) under Contract Nonr-3963(02)-Task 2Lincoln Laboratory, Purchase Order DDL B-00368U. S. NavyU. S. ArmyU. S. Air Force under Air Force Contract AF19(604)-7400National Aeronautics and Space Administration (Grant NsG-250-62)National Aeronautics and Space Administration (Contract NaSr-101

A scanning tunneling microscope capable of electron spin resonance and pump-probe spectroscopy at mK temperature and in vector magnetic field

In the last decade, detecting spin dynamics at the atomic scale has been enabled by combining techniques like electron spin resonance (ESR) or pump-probe spectroscopy with scanning tunneling microscopy (STM). Here, we demonstrate an ultra-high vacuum (UHV) STM operational at milliKelvin (mK) and in a vector magnetic field capable of both ESR and pump-probe spectroscopy. By implementing GHz compatible cabling, we achieve appreciable RF amplitudes at the junction while maintaining mK base temperature. We demonstrate the successful operation of our setup by utilizing two experimental ESR modes (frequency sweep and magnetic field sweep) on an individual TiH molecule on MgO/Ag(100) and extract the effective g-factor. We trace the ESR transitions down to MHz into an unprecedented low frequency band enabled by the mK base temperature. We also implement an all-electrical pump-probe scheme based on waveform sequencing suited for studying dynamics down to the nanoseconds range. We benchmark our system by detecting the spin relaxation time T1 of individual Fe atoms on MgO/Ag(100) and note a field strength and orientation dependent relaxation time

Thermal roughening of an SOS-model with elastic interaction

We analyze the effects of a long-ranged step-step interaction on thermal roughening within the framework of a solid-on-solid model of a crystal surface by means of Monte Carlo simulation. A repulsive step-step interaction is modeled by elastic dipoles located on sites adjacent to the steps. In order to reduce the computational effort involved in calculating interaction energy based on long-ranged potentials, we employ a multi-grid scheme. As a result of the long-range character of the step interaction, the roughening temperature increases drastically compared to a system with short-range cutoff as a consequence of anti-correlations between surface defects

Solid-State Microwave Electronics

Contains reports on status of research and nine research projects.National Aeronautics and Space Administration (Grant NGR-22-009-163

Solid-State Microwave Electronics

Contains research objectives and reports on status of research projects.National Aeronautics and Space Administration (Grant NGR-22-009-163

Skewness and kurtosis of net baryon-number distributions at small values of the baryon chemical potential

We present results for the ratios of mean (MB), variance (σ2B), skewness (SB) and kurtosis (κB) of net baryon-number fluctuations obtained in lattice QCD calculations with physical values of light and strange quark masses. Using next-to-leading order Taylor expansions in baryon chemical potential we find that qualitative features of these ratios closely resemble the corresponding experimentally measured cumulant ratios of net proton-number fluctuations for beam energies down to √sNN≥19.6  GeV. We show that the difference in cumulant ratios for the mean net baryon-number, MB/σ2B=χB1(T,μB)/χB2(T,μB), and the normalized skewness, SBσB=χB3(T,μB)/χB2(T,μB), naturally arises in QCD thermodynamics. Moreover, we establish a close relation between skewness and kurtosis ratios, SBσ3B/MB=χB3(T,μB)/χB1(T,μB) and κBσ2B=χB4(T,μB)/χB2(T,μB), valid at small values of the baryon chemical potential

Entanglement-based quantum communication secured by nonlocal dispersion cancellation

Quantum key distribution (QKD) enables participants to exchange secret information over long distances with unconditional security. However, the performance of today's QKD systems is subject to hardware limitations, such as those of available nonclassical-light sources and single-photon detectors. By encoding photons in high-dimensional states, the rate of generating secure information under these technical constraints can be maximized. Here, we demonstrate a complete time-energy entanglement-based QKD system with proven security against the broad class of arbitrary collective attacks. The security of the system is based on nonlocal dispersion cancellation between two time-energy entangled photons. This resource-efficient QKD system is implemented at telecommunications wavelength, is suitable for optical fiber and free-space links, and is compatible with wavelength-division multiplexing.United States. Army Research Office (Defense Advanced Research Projects Agency. Information in a Photon (InPho) Program (Grant W911NF-10-1-0416))National Science Foundation (U.S.). Integrative Graduate Education and Research Traineeship (Grant DGE-1069420