Physics & Astronomy News
An unusual onset of agminated Spitz naevi in an adult patient
By: Adler, N. R.; Kelly, J. W.; Dowling, J. P.; et al. CLINICAL AND EXPERIMENTAL DERMATOLOGY, Volume: 43, Issue: 3, Pages: 363-365. Published: APR 2018
A. R. P. Rau: “Calculation of quantum discord in higher dimensions for X- and other specialized states,” Quantum Inf. Processing 17, 216 (18 pp) (2018)
Quantum discord, a kind of quantum correlation based on entropic measures, is definedas the difference between quantum mutual information and classical correlation in abipartite system. Procedures are available for analytical calculation of discord whenone of the parties is a qubit with dimension two and measurements made on it to get thatone-way discord. We extend now to systems when both parties are of larger dimensionand of interest to qudit–quDit with d, D ≥ 3 or spin chains of spins ≥ 1. Whilerecognizing that no universal scheme is feasible, applicable to all density matrices,nevertheless, a procedure similar to that for d = 2 that works for many mixed-statedensity matrices remains of interest as shown by recent such applications. We focus onthis method that uses unitary operations to describe measurements, reducing them toa compact form so as to minimize the number of variables needed for extremizing theclassical correlation, often the most difficult part of the discord calculation. Resultsare boiled down to a simple recipe for that extremization; for some classes of densitymatrices, the procedure even gives trivially the final value of the classical correlationwithout that extremization. A qutrit–qutrit (d = D = 3) system is discussed in detailwith specific applications to density matrices for whom other calculations involveddifficult numerics. Special attention is given to the so-called X-states and Wernerand isotropic states when the calculations become particularly simple. An appendixdiscusses an independent but related question of the systematics of X-states of arbitrarydimension. It forms a second, separate, part of this paper, extending our previousgroup-theoretic considerations of systematics for qubits now to higher d.
"Conditional Decoupling of Quantum Information" by Mark M. Wilde et al. Phys. Rev. Lett. 121, 040504 – Published 27 July 2018
Insights from quantum information theory show that correlation measures based on quantum entropy are fundamental tools that reveal the entanglement structure of multipartite states. In that spirit, Groisman, Popescu, and Winter [Phys. Rev. A 72, 032317 (2005)] showed that the quantum mutual information I ( A ; B ) quantifies the minimal rate of noise needed to erase the correlations in a bipartite state of quantum systems A B . Here, we investigate correlations in tripartite systems A B E . In particular, we are interested in the minimal rate of noise needed to apply to the systems A E in order to erase the correlations between A and B given the information in system E , in such a way that there is only negligible disturbance on the marginal B E . We present two such models of conditional decoupling, called deconstruction and conditional erasure cost of tripartite states A B E . Our main result is that both are equal to the conditional quantum mutual information I ( A ; B | E ) —establishing it as an operational measure for tripartite quantum correlations.
Summer 2018 Graduates
On Friday, August 3, LSU Physics & Astronomy welcomed three new PhD graduates who were awarded their degrees at the Marvavich Assembly Center. They are John Chapman, Jonathan Cripe, and Joseph Steiner
LSU Medical Physics Student Elizabeth Hilliard Receives 1st Place at LSU Three Minute Thesis Competition
Meet Elizabeth Hilliard, a medical physics graduate from the LSU Department of Physics and Astronomy, whose M.S. project was working to improve the efficiency and control of electron beam exposure in cancer patients needing radiation therapy. Elizabeth has undergraduate degrees in both physics and psychology from Rensselaer Polytechnic Institute. She recently won the LSU Three Minute Thesis (#3MT) competition by presenting a winning story about her research on stage for the LSU Graduate School, and moved on to compete in the regional 3MT competition in Fayetteville, AR.
"Efficient optimization of state preparation in quantum networks using quantum trajectories." Michael Goerz and Kurt Jacobs. Quantum Science and Technology, Volume 3, Number 4
The wavefunction Monte-Carlo method, also referred to as the use of 'quantum jump trajectories', allows efficient simulation of open systems by independently tracking the evolution of many pure-state 'trajectories'. This method is ideally suited to simulation by modern, highly parallel computers. Here we show that Krotov's method of numerical optimal control, unlike others, can be modified in a simple way so that it becomes fully parallel in the pure states without losing its effectiveness. This provides a highly efficient method for finding optimal control protocols for open quantum systems and networks. We apply this method to the problem of generating entangled states in a network consisting of systems coupled in a unidirectional chain. We show that due to the existence of a dark state subspace in the network, nearly optimal control protocols can be found for this problem by using only a single pure-state trajectory in the optimization, further increasing the efficiency.
Energy Department Funds $10 Million University Nuclear Research Center
LSU physicist among the two dozen researchers funded
"Extended Measurement of the Cosmic-Ray Electron and Positron Spectrum from 11 GeV to 4.8 TeV with the Calorimetric Electron Telescope on the International Space Station”, Adriani, Cannady, Cherry, Guzik, Wefel et al., Phys. Rev. Lett. 120, 261102 (2018)
Extended results on the cosmic-ray electron + positron spectrum from 11 GeV to 4.8 TeV are presented based on observations with the Calorimetric Electron Telescope (CALET) on the International Space Station utilizing the data up to November 2017. The analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. CALET is an all- calorimetric instrument with a total thickness of 30 radiation lengths at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum in the region below 1 TeV shows good agreement with Alpha Magnetic Spectrometer (AMS-02) data. In the energy region below ∼300 GeV, CALET’s spectral index is found to be consistent with the AMS-02, Fermi Large Area Telescope (Fermi-LAT), and Dark Matter Particle Explorer (DAMPE), while from 300 to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The absolute flux of CALET is consistent with other experiments at around a few tens of GeV. However, it is lower than those of DAMPE and Fermi-LAT with the difference increasing up to several hundred GeV. The observed energy spectrum above ∼1 TeV suggests a flux suppression consistent within the errors with the results of DAMPE, while CALET does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 TeV. Our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the Supplemental Material in order to allow more refined spectral analyses based on our data.
"Detection of the Thermal Component in GRB 160107A", Y. Kawakubo, M. Cherry et al., Publ. Astronom. Soc. Japan 70, 6 (2018)
We present the detection of a blackbody component in GRB 160107A emission by using the combined spectral data of the CALET Gamma-ray Burst Monitor (CGBM) and the MAXI Gas Slit Camera (GSC). The MAXI/GSC detected the emission ∼45 s prior to the main burst episode observed by the CGBM. The MAXI/GSC and the CGBM spectrum of this prior emission period is well fit by a blackbody with the temperature of 1.0+0.3−0.2 keV plus a power-law with the photon index of −1.6±0.3. We discuss the radius to the photospheric emission and the main burst emission based on the observational properties. We stress the importance of the coordinated observations via various instruments collecting the high quality data over a broad energy coverage in order to understand the GRB prompt emission mechanism.
LIGO Livingston to Be Designated a Historic Site
The Laser Interferometer Gravitational Wave Observatory, or LIGO, in Livingston, La., will be designated a historic physics site by the American Physical Society, or APS, on Wednesday, June 20. Media are invited to attend this special ceremony beginning at 11 a.m. To RSVP, email the media relations contacts below. LIGO Livingston is one of two observatories in the U.S. that made the first direct observations of gravitational waves emanating from violent and distant astronomical events. The two observatories — one in Louisiana and the other in Hanford, Wash. — will receive plaques to recognize the extraordinary efforts that led to this detection.
Alumnus $1 million bequest to LSU Physics & Astronomy will help future Tigers
Dr. Rick Rauch (Science, ’77), an expert in rocket propulsion testing, will provide a $1 million bequest to establish an endowed research scholarship fund for the LSU Department of Physics & Astronomy. A product of the 1960s, Rauch is living his childhood dream as project manager at NASA’s John C. Stennis Space Center.
Alumnus Mark DiTusa Awarded National Science Foundation Graduate Research Fellowship
2016 LSU graduate, Mark DiTusa, is the recipient of the 2018 National Science Foundation Graduate Research Fellowship Program, or GRFP. This fellowship from the National Science Foundation helps ensure the vitality of the human resource base of science and engineering in the U.S. and reinforces its diversity. DiTusa is currently pursuing his Ph.D. at the University of Chicago.
"Strong and uniform convergence in the teleportation simulation of bosonic Gaussian channels" by Mark Wilde. Phys. Rev. A 97, 062305
In the literature on the continuous-variable bosonic teleportation protocol, it is often loosely stated that it converges to a perfect teleportation of an input quantum state in the limit of ideal squeezing and ideal detection, but the exact form of this convergence is typically not clarified. In this work, Prof. Wilde explicitly clarifies that the convergence is in the strong sense, and not the uniform sense, and furthermore that the convergence occurs for any input state to the protocol, including the infinite-energy Basel states defined and discussed in this work. Prof. Wilde also proves, in contrast to the above result, that the teleportation simulations of pure-loss, thermal, pure-amplifier, amplifier, and additive-noise channels converge both strongly and uniformly to the original channels, in the limit of ideal squeezing and detection for the simulations. For these channels, he gives explicit uniform bounds on the accuracy of their teleportation simulations. These uniform convergence results are then extended to particular multimode bosonic Gaussian channels. These convergence statements have important implications for mathematical proofs that make use of the teleportation simulation of bosonic Gaussian channels, some of which have to do with bounding their nonasymptotic secret-key-agreement capacities.
California High School Students to Present New Findings on Tabby’s Star
A team of high school students will present new findings on KIC 8462852, or Tabby’s Star, often referred to as the most mysterious star in the universe, at a press conference at the American Astronomical Society meeting in Denver, Colo. today. Tabby’s Star is nicknamed after LSU Department of Physics & Astronomy Assistant Professor Tabetha Boyajian, who has observed and studied the unusual dimming and brightening of this otherwise ordinary star along with citizen scientists.
"The Montevideo Interpretation of Quantum Mechanics: A Short Review" by Gambini and Pullin. Entropy 2018, 20(6), 413
The Montevideo interpretation of quantum mechanics, which consists of supplementing environmental decoherence with fundamental limitations in measurement stemming from gravity, has been described in several publications. However, some of them appeared before the full picture provided by the interpretation was developed. As such, it can be difficult to get a good understanding via the published literature. Here, we summarize it in a self-contained brief presentation including all its principal elements
LSU Physics Professor Named Visiting Professor of Chinese Academy of Sciences
BATON ROUGE - LSU Professor Jonathan P. Dowling has been appointed to a three-year term as Distinguished Visiting Professor of the Chinese Academy of Sciences. Dowling is the Horace C. Hearne Professor of Theoretical Physics and founding Co-Director of the Horace C. Hearne Institute for Theoretical Physics in the LSU College of Science. The Institute carries out research on quantization of gravity, quantum optics effects in gravitational wave interferometers, decoherence due to quantum gravity, non-standard optics due to quantum gravity, quantum computing, quantum imaging, and quantum sensing.
Spring 2018 Graduates
On Friday, May 11, LSU Physics & Astronomy welcomed 3 new PhD, 2 MS and 14 BS graduates who received their diplomas at the Pete Maravich Assembly Center and Maddox Fieldhouse.
2018 Annual Physics & Astronomy Awards
2018 University Distinguished Faculty Awards and Annual Physics & Astronomy Awards
LSU Physics Students Receive NRC Scholarship in Health Physics
LSU's Department of Physics & Astronomy has announced Rebecca DiTusa and Khang Pham as recipients of the NRC scholarship program in health physics. A grant from the U.S. Nuclear Regulatory Commission (NRC) was established at LSU in 2017 supporting undergraduate students to explore careers in the radiation sciences through the field of health physics.
Physics Nobel Laureate Rainer Weiss to Speak at LSU College of Science Spring Diploma Ceremony, May 11
Rainer Weiss, 2017 Nobel Laureate in Physics, MIT Physics Professor Emeritus, and LSU adjunct professor in physics and astronomy, will serve as the keynote speaker for the LSU College of Science spring ceremony, Friday, May 11 at 12 p.m. in Maddox Field House.