Foiling Quantum Hackers

Quantum cryptography holds promise for communication schemes that are, in theory, perfectly secure. But in the last few years, hackers have exploited security loopholes to crack some of the most sophisticated quantum encryption systems. Fortunately, two new papers in Physical Review Letters, one by Allison Rubenok, at the Institute for Quantum Science & Technology in Calgary, Canada, and colleagues [1] and the other by Yang Liu, at the Hefei National Laboratory for Physical Sciences and the University of Science and Technology of China, and colleagues [2] now report a new quantum encryption method that can remove the weakest link of quantum encryption schemes: loopholes associated with defects of the photodetectors used at the receiver end. Code makers have now regained the upper hand against code breakers.

Code makers and code breakers have been fighting for thousands of years. With the rise of the Internet, the importance of communication security is growing. Each time we do online banking or use messaging apps on our smart phones, we should be concerned about communication security. Conventional (classical) cryptographic systems are often based on unproven computational assumptions.

In contrast, quantum encryption methods such as quantum key distribution (QKD)—the use of quantum states to transmit a shared encryption key between communicating parties—offer, in principle, unconditional security based on the laws of physics. This is an ideal solution in the long term, but we are not there yet: while QKD schemes have been demonstrated and have already led to commercially available products, a few research groups, in the last few years, have reported a number of high-profile successful hacks [3] against QKD systems, thus casting doubts on the security of practical QKD. Charles Bennett [4], an IBM Fellow and a co-inventor of quantum cryptography, wrote: “Photon detectors have turned out to be an Achilles’ heel for quantum key distribution (QKD), inadvertently opening the door … to subtle side-channel attacks.”

In one hacking example, Eve (the eavesdropper) can blind the detectors of Bob (the receiver) with a low-power, continuous-wave laser. While the detector is blinded, it works as a classical detector and loses the “quantum” protection: Eve can then intercept, unnoticed, Alice’s (the sender’s) signals. Countermeasures for quantum hacking have been proposed—such as security patches [5], teleportation tricks [6], and full device-independent QKD (DI-QKD) [7]—but all have been proven to be either ad hoc or impractical, e.g., not compatible with long-distance communications or with key generation at sufficient speeds.

Magnetic behavior discovery could advance nuclear fusion

Fusion is widely considered the ultimate goal of nuclear energy. While fission leaves behind radioactive waste that must be stored safely, fusion generates helium, a harmless element that is becoming scarce. Just 250 kilograms of fusion fuel can match the energy production of 2.7 million tons of coal.

Unfortunately, it is very difficult to get a fusion reaction going.

"We have to compress the fuel to a temperature and density similar to the core of a star," said Alexander Thomas, assistant professor of nuclear engineering and radiological sciences.

Once those conditions are reached, the hydrogen fuel begins to fuse into helium. This is how young stars burn, compressed by their own gravity.

On Earth, it takes so much power to push the fuel atoms together that researchers end up putting in more energy than they get out. But by understanding a newly discovered magnetic phenomenon, the team suggests that the ignition of nuclear fusion could be made more efficient.

Two methods dominate for confining the fuel, made of hydrogen atoms with extra neutrons, so that fusion can begin. Magnetic confinement fusion uses magnetic fields to trap the fuel in a magnetic 'bottle,' and inertial confinement fusion heats the surface of the fuel pellet until it blows off in a way that causes the remaining pellet to implode. The team explored an aspect of the latter method through computer simulations.

"One of the concerns with nuclear fusion is to squeeze this very spherical fuel pellet perfectly into a very small spherical pellet," said Archis Joglekar, a doctoral student in nuclear engineering and radiological sciences.

To avoid pushing the ball of fuel into an irregular shape that won't ignite, the fuel must be exposed to uniform heat that will cause its surface layer to evaporate all at once. As this layer pushes off at high speed, it applies equal pressure to all sides of the pellet and causes it to shrink to one thousandth of its original volume. When that happens, the fuel begins to fuse.

Joglekar calls even heating "the biggest concern in terms of achieving inertial confinement fusion."

The heat comes from about 200 laser beams hitting the inside of a hollow metal cylinder with the fuel pellet sitting at its heart. The trouble is that the light energy from the laser is converted to heat in the metal by way of electrons, and the electrons can get trapped in magnetic fields created by the laser spots.

When the laser light hits the metal, it turns some of the surface metal into plasma, or a soup of electrons and free atomic nuclei. The laser and the heat drive the electrons to move in a way that sets up a magnetic field circling the laser spot.

The magnetic field acts as a boundary for the electrons -- they can't cross it. But until now, researchers didn't know that the hot electrons, in an effort to get to cooler areas, are able to push the magnetic fence outward.

The team showed that the flow of hot electrons could drive the magnetic fields around neighboring laser spots together, causing them to join up. Instead of forming a barrier between the laser spots, the joined fields open a channel between them.

"Now there's a clear path for the electrons to move into what would otherwise be the cold region," Joglekar said.

Designers of inertial fusion ignition systems may be able to use this newly discovered feature to place the laser spots so that they heat the cylinder more quickly and efficiently.

"Essentially, what we found is a completely new magnetic reconnection mechanism," Thomas said. "Though we're studying it in an inertial confinement fusion process, it might be relevant to the surface of the sun and magnetic confinement fusion."

For instance, knowing that the flow of hot, charged particles on the sun can push magnetic fields around could inspire new theories about how solar flares occur.

A paper on this work, titled "Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law," is published in Physical Review Letters. It was carried out in collaboration with Amativa Bhattacharjee and William Fox of the Princeton Plasma Physics Laboratory.

Imaging Single Photons from a Kilometer Away

Scientists in Scotland have developed an imaging technique that can capture 3-D information of single photons at distances of a kilometer, adding to the remarkable progress of single-photon detectors in the past decade. Gerard Buller and colleagues at Heriot-Watt University in Edinburgh designed and tested a prototype multispectral lidar system using a time-correlated single-photon counting technique to recover millimeter-scale information about the structure and physiology of remote objects. The technique was tested on fir tree samples and was found to be practical for 3-D imaging from airborne and space-based imaging platforms (IEEE Trans. DOI: 10.1109/TGRS.2013.2285942).

The time-of-flight lidar system uses a supercontinuum laser source emitting simultaneously at 531 nm, 570 nm, 670 nm and 780 nm at a laser repetition rate of 2 MHz. Four thick-junction-silicon single-photon avalanche diode detectors construct 3-D images of targets a kilometer away using the absolute minimum of pulsed laser power—less than 200 µW total exiting the system. The system worked in bright sunny conditions to retrieve data less than 1 cm in resolution from a 3 mm beam spot.

“The solar background is by far the highest contribution to background which can swamp the return signal if the system is not engineered properly,” said Buller. “Even in Scotland, it is sunny occasionally!”

With an x-y system spatial resolution of 50 µrad and a z-resolution of 1 cm, such an array of single-photon detectors collects vast amounts of data in a time-efficient manner, but presents a bottleneck in data processing. According to Buller, more efficient imaging processing algorithms and recent work in “first-photon imaging” at MIT have shown a potentially exciting route to using less data, which reduces acquisition time and improves processing efficiency.

The researchers say the imaging technique has many applications, such as forest mapping for environmental study. The technique lends itself to imaging in scattering media, such as underwater depth imaging, collision monitoring in moving vehicles and a host of others in a wide variety of fields. Harnessing multi-spectral single-photon depth imaging from aircraft could provide an insight into the carbon cycle—but major issues remain in providing sufficient multi-spectral data from a moving platform.

Penn State Students Seek Crowdfunding To Land A Hopping Rover On The Moon

Just before winter break, students at Pennsylvania State University sat in a control room behind a two-foot-thick concrete wall. On the other side of the wall was a cryogenic rocket. As the rocket fired away, the students measured the temperature and pressure in different parts of the system, including fixtures they'd built for the rocket, all with their own handwritten computer code.

They were part of the Lunar Lion team, one of 18 teams still in the running for the Google Lunar XPrize. Lunar Lion is also the only team based at a university and comprised mostly of college students, led by Penn State staff and faculty. (Although at least one other team is a spinoff from a university.) If the Penn State students win, they could earn up to $20 million for their school. They'll also have to have landed a rover on the moon, driven the rover at least 500 meters, and sent high-definition videos and photos back to Earth. Whichever team wins the grand prize, if any, will be only the fourth "team"—after the space agencies of the former Soviet Union, the U.S., and China—to make a soft landing on the moon.

"Our goal is really education and research," Michael Paul, Lunar Lion's director and a space systems engineer at Penn State's Applied Research Laboratory, tells Popular Science. "What we're doing, we hope, becomes a model for other universities." Paul means in terms of funding. The Google Lunar XPrize is meant to stimulate the private spaceflight industry, so it requires its contestants be privately funded. The Lunar Lion team gets support from corporate and private donations and tries to work on a lean budget, Paul says. "One of the things that the students are learning is how to be frugal in their engineering."

Landing at Moon

The overall design is an all-in-one model that combines lander and rover in one vehicle. That helps save money—"otherwise we'd have to build, test and pay for essentially for two spacecraft, two spacecraft that would be bolted together," Paul says. The Lunar Lion craft will land on the surface of using small rockets, then use those same engines to "hop" the required 500 meters to win the prize. Although NASA's recent Mars rovers have been wheeled, a hopping design could help the Lunar Lion move more quickly and agilely. 

I talked briefly with Alwin Paul, an undergraduate engineering major who leads a Lunar Lion design team with another undergrad engineer, Patrick Gorski. Alwin Paul (no relation to Michael Paul) explained he's responsible for making a hovercraft that will allow him to test the craft's avionics. His group will also test the craft's individual components, including a set of feet with a honeycomb structure that will collapse as the craft lands on the surface of the moon. The honeycomb feet need to absorb 13 Gs of impact and protect the craft's delicate equipment as it lands.

The team has a little less than two years to get ready to fly. Michael Paul and his students have bought the $10 million ticket they need to hitch a ride with Phoenicia, a private launch provider based in California. They're going up in a launch window around December 19, 2015

LaTeX

%Latex is the better option for any document typing because it is unicode and free of virus also you can create PDF %using this.
%
% latex-sample.tex
%
% This LaTeX source file provides a template for a typical research paper.
%

%
% Use the standard article template.
%
\documentclass{article}

% The geometry package allows for easy page formatting.
\usepackage{geometry}
\geometry{letterpaper}

% Load up special logo commands.
\usepackage{doc}

% Package for formatting URLs.
\usepackage{url}

% Packages and definitions for graphics files.
\usepackage{graphicx}
\usepackage{epstopdf}
\DeclareGraphicsRule{.tif}{png}{.png}{`convert #1 `dirname #1`/`basename #1 .tif`.png}

%
% Set the title, author, and date.
%
\title{Sample \LaTeX-Based Research Paper}
\author{Rajeev Chaubey}
\date{}

%
% The document proper.
%
\begin{document}

% Add the title section.
\maketitle

% Add an abstract.
\abstract{
Describe your paper in 100-200 words, give or take.  The command-line \texttt{wc} utility is really useful here!  This particular sample paper is meant to demonstrate a variety of \LaTeX\ directives for producing a well-structured, consistently-formatted scholarly document.  The actual content and outline may vary according to the needs of your specific research topic.
}

% Add various lists on new pages.
\pagebreak
\tableofcontents

\pagebreak
\listoffigures

\pagebreak
\listoftables

% Start the paper on a new page.
\pagebreak

%
% Body text.
%
\section{Introduction}
\label{introduction}

You will almost certainly start with an introductory description of the topic that you investigated in your assignment.  Discuss any goals, motivation, or examples of the subject; the key is to provide the reader with any information that is necessary to understand why your topic was worth investigating.  This descriptive section should also allow the reader to understand the subsequent detail sections on the subject.

\section{Background, Preliminary, and Related Work}

Perhaps the most important functionality to learn for the paper is \LaTeX\ bibliography support.  Citations and references are handled automatically by \LaTeX\ through its companion program, \BibTeX.  All you have to do is provide a bibliography file that provides the reference information and internal keys (very much like variable names) that you use in your document.\footnote{And always remember to run \LaTeX\ \emph{at least twice} after running \BibTeX.}

\BibTeX\ supports virtually all kinds of references, including books \cite{dui,sgg,iokit,palmos}, parts of books \cite{userModeLinux}, articles \cite{nielsen:dui-review,heer-shneiderman,stackableThreads,xpkernel}, and conference proceedings \cite{ux-3d,iring,contextFileSearch,osHaskell,hibernator}, to name a few.  If not already included in your \LaTeX\ distribution, download and install the \texttt{url} package to support formatting of URLs; you can usually mention these in the \emph{note} or \emph{howpublished} fields of your \BibTeX\ file.

Like Section~\ref{introduction}, a background, preliminary, and related work section is also almost certainly needed for your paper.  In this section, describe any history, work, or projects that serve as direct contributors to the subject of your research paper.  Look at other papers in the literature to see how they organized, presented, and discussed prior work.

The Shneiderman/Plaisant text \cite{dui} provide some pointers to seminal or key works; because they made it into the textbook they aren't necessarily ``bleeding edge,'' but they likely provide the foundation for your chosen subject matter.

\section{Main Content Sections}

The outline after the introductory and background, preliminary, and related work sections is more dependent on the specific subject of your research.  Remember to cite references where appropriate, organize the material so that it flows well and is clear to the reader.

\subsection{Multiple Outline Levels}

\LaTeX\ has support for up to three outline levels (\verb!\section!, \verb!\subsection!, and \verb!\subsubsection!).  It also recognizes \verb!\paragraph! and \verb!\subparagraph! directives, though those don't show up in the table of contents.  All of these directives expect a title.

Note also the use of the \verb!\verb! directive for inserting code-like labels or symbols.  It was particularly needed here so that we can include the backslash character in the text.

\subsection{Tables and Figures}

\LaTeX\ has full support for tables and figures.  Table~\ref{table-sample} shows a sample table and Figure~\ref{figure-sample} shows a sample figure.  Note the built-in support for captions and the automated numbering functionality.  Lists of tables and figures can also be automatically generated, as seen at the beginning of this document.

\begin{table}
\centering
\begin{tabular}{|c|c|c|}\hline
Column 1 & Column 2 & Column 3 \\\hline\hline
a & b & c \\
d & e & f \\
g & h & i \\\hline
\end{tabular}

\caption{A sample table}
\label{table-sample}
\end{table}

\begin{figure}
\centering
\includegraphics[width=2in]{space.jpg} 

\caption{A sample figure}
\label{figure-sample}
\end{figure}

One very important thing to remember about how \LaTeX\ handles tables and figures by default: you don't have to worry about where they go exactly.  The general rule is that you insert them in the source after your first reference to them, and \LaTeX\ determines their final position.  It also makes decisions on how much page space to devote to them.  This all follows \LaTeX's overall theme of focusing on the content of your paper, and not its format.

Just so you can see a second table, Table~\ref{table-sample2} is provided.

\begin{table}
\centering
\begin{tabular}{|c|c|c|}\hline
Column 1 & Column 2 & Column 3 \\\hline\hline
a & b & c \\
d & e & f \\
g & h & i \\\hline
\end{tabular}

\caption{Another sample table}
\label{table-sample2}
\end{table}

\section{Another Section}

We're adding another section just so you can see how that looks.  Plus there are a few more \LaTeX\ features to illustrate.

\subsection{Bulleted and Numbered Lists}

\LaTeX\ is very good at providing clean lists.  Examples are shown below.

\begin{itemize}
\item Bulleted items come out properly indented and spaced, every time.

\begin{itemize}
\item Sub-bullets are a virtual no-brainer: just nest another \verb!itemize! block.
\item Note how the bullet character automatically changes too.
\end{itemize}

\item Just keep on adding \verb!\item!s\ldots

\item \ldots until you're done.
\end{itemize}

Numbered lists are almost identical, except that you specify \verb!enumerate! instead of \verb!itemize!.  List items are specified in exactly the same way (thus making it easy to change list types).

\begin{enumerate}
\item A list item
\item Another list item
\item A list item with multiple nested lists

\begin{itemize}
\item Nested lists can be of mixed types.
\item That's a lot of power and flexibility for the price of learning a handful of directives.

\begin{enumerate}
\item Like nested bullet lists, nested numbered lists also ``intelligently'' change their numbering schemes.
\item Meanwhile, all \emph{you} have to write is \verb!\item!.  \LaTeX\ does the rest.
\end{enumerate}
\end{itemize}

\item Back to your regularly scheduled list item

\end{enumerate}

\subsection{Subsection with Another Figure}

We may as well include a second figure also, shown in Figure~\ref{figure-sample2}.  The same image file is used, but note how it can be resized.  Again, observe how the positions of the tables and figures do not necessarily match their positions in the source file, reiterating the aforementioned \LaTeX\ functionality for deciding where these items go in the final document.  You provide an approximate location, and \LaTeX\ does the rest.

\begin{figure}
\centering
\includegraphics[width=1in]{space.jpg} 

\caption{Another sample figure}
\label{figure-sample2}
\end{figure}

\section{Conclusion}

Wrap up your paper with an ``executive summary'' of the paper itself, reiterating its subject and its major points.  If you want examples, just look at the conclusions from the literature.

% Generate the bibliography.
\bibliography{latex-sample}
\bibliographystyle{unsrt}

\end{document}

First ever DBM trained using a quantum computer

In Terminator 2, Arnold reveals that his CPU is a neural net processor, a learning computer. Of course it is! What else would it be? Interestingly, there are real neural net processors in the world. D-Wave makes the only superconducting version, but there are other types out there also. Today we’ll use one of our superconducting neural nets to re-run the three experiments we did last time.

I believe this is the first time quantum hardware has been used to train a DBM, although there have been some theoretical investigations.

Embedding into hardware

Recall that the network we were training in the previous post had one visible layer with up to four units, and two hidden layers each with four units. For what follows we’re going to associate each of these units with a specific qubit in a Vesuvius processor. The way we’re going to do this is to use a total of 16 qubits in two unit cells to represent the 12 units in the DBM.

All D-Wave processors can be thought of as hardware neural nets, where the qubits are the neurons and the physical couplers between pairs of qubits are edges between qubits.Specifically you should think of them as a type of Deep Boltzmann Machine (DBM), where specifying the biases and weights in a DBM is exactly like specifying the biases and coupling strengths in a D-Wave processor. As in a DBM, what you get out are samples from a probability distribution, which are the (binary) states of the DBM’s units (both visible and hidden).

In the Vesuvius design, there is an 8×8 tile of eight-qubit unit cells, for a total of 512 ‘neurons’. Each neuron is connected to at most 6 other neurons in Vesuvius. To do the experiments we want to do, we only need two of the 64 unit cells. For the experts out there, we could use the rest to do some interesting tricks to use more of the chip, such as gauge transformations and simple classical parallelism, but for now we’ll just stick to the most basic implementation.

Tech fest

Successful launch of Sentinel-1A – the satellite carries optical systems of the Berliner Glas Group

On 03 April 2014, shortly after 11:00 p.m., Sentinel-1A, a polar-orbiting satellite, was launched successfully on a Soyuz rocket from Europe’s Spaceport Kourou in French Guiana.

Sentinel-1A is the first satellite of the ESA Sentinel fleet, that has been developed specifically to provide large amounts of data and pictures for the Earth observation program Copernicus. Sentinel-1A will orbit the Earth at an altitude of a few hundred kilometers (in a low Earth orbit) and will provide all-weather, day and night radar imagery for land and ocean services.

A laser communications terminal (LCT) of Tesat-Spacecom also is on board Sentinel-1A. This laser communications terminal includes several optical components and systems of the Berliner Glas Group. These high-precision opto-mechanical systems designed and produced by the Berliner Glas Group at its locations in Berlin, Germany and Heerbrugg, Switzerland guide and process the laser light in the transmission as well as receiver channels of the laser communications terminal. The highest requirements had to be realized to ensure an error-free operation during the entire lifetime of the satellite in space.

The laser communications terminal on board Sentinel-1A is another component of the European Data Relay System (EDRS) and enables high-speed data transfers between the low Earth orbit and the geostationary Earth orbit. The first high-volume data connection between the laser communications terminal on Sentinel-1A and a satellite in geostationary Earth orbit is expected to be realized later on this year.