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ESE Seminar: Ying Wang, PhD,-PhD-.aspxESE Seminar: Ying Wang, PhD2020-01-30T06:00:00Z
ESE Seminar: Jun-Chau Chien, PhD,-PhD.aspxESE Seminar: Jun-Chau Chien, PhD2020-02-04T06:00:00Z
ESE Seminar: Data Analytics and Bayer Seminar: Data Analytics and Bayer 2020-02-07T06:00:00Z

Research Highlights
 optical resonators gives researchers control over transparency<img alt="" src="/news/PublishingImages/EITUpdate.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>In the quantum realm, under some circumstances and with the right interference patterns, light can pass through opaque media.</p><p>This feature of light is more than a mathematical trick; optical quantum memory, optical storage and other systems that depend on interactions of just a few photons at a time rely on the process, called electromagnetically induced transparency, also known as EIT.  </p><p>Because of its usefulness in existing and emerging quantum and optical technologies, researchers are interested in the ability to manipulate EIT without the introduction of an outside influence, such as additional photons that could perturb the already delicate system. Now, researchers at the McKelvey School of Engineering at Washington University in St. Louis have devised a fully contained optical resonator system that can be used to turn transparency on and off, allowing for a measure of control that has implications across a wide variety of applications.<br/></p><p>The group published the results of the research, conducted in the lab of Lan Yang, the Edwin H. & Florence G. Skinner Professor in the Preston M. Green Department of Electrical & Systems Engineering, in a paper titled <a href="">Electromagnetically Induced Transparency at a Chiral Exceptional Point</a> in the Jan. 13 issue of <em>Nature Physics</em>.</p><p>An optical resonator system is analogous to an electronic resonant circuit but uses photons instead of electrons. Resonators come in different shapes, but they all involve reflective material that captures light for a period of time as it bounces back and forth between or around its surface. These components are found in anything from lasers to high precision measuring devices.</p><p>For their research, Yang’s team used a type of resonator known as a whispering gallery mode resonator (WGMR). It operates in a manner similar to the whispering gallery at St. Paul’s Cathedral, where a person on one side of the room can hear a person whispering on the other side. What the cathedral does with sound, however, WGMRs do with light — trapping light as it reflects and bounces along the curved perimeter.</p><p>In an idealized system, a fiber optic line intersects with a resonator, a ring made of silica, at a tangent. When a photon in the line meets the resonator, it swoops in, reflecting and propagating along the ring, exiting into the fiber in the same direction it was initially headed.</p><p>Reality, however, is rarely so neat.</p><p>“Fabrication in high quality resonators is not perfect,” Yang said. “There is always some defect, or dust, that scatters the light.” What actually happens is some of the scattered light changes direction, leaving the resonator and travelling back in the direction whence it came. The scattering effects disperse the light, and it doesn’t exit the system.</p><p>Imagine a box around the system: If the light entered the box from the left, then exited out the right side, the box would appear transparent. But if the light that entered was scattered and didn’t make it out, the box would seem opaque.</p><p>Because manufacturing imperfections in resonators are inconsistent and unpredictable, so too was transparency. Light that enters such systems scatters and ultimately loses its strength; it is absorbed into the resonator, rendering the system opaque.</p><p>In the system devised by co-first authors Changqing Wang, a PhD candidate, and Xuefeng Jiang, a researcher in Yang’s lab, there are two WGMRs indirectly coupled by a fiber optic line. The first resonator is higher in quality, having just one imperfection. Wang added a tiny pointed material that acts like a nanoparticle to the high-quality resonator. By moving the makeshift particle, Wang was able to “tune” it, controlling the way the light inside scatters.</p><p>Importantly, he was also able to tune the resonator to what’s known as an “exceptional point,” a point at which one and only one state can exist. In this case, the state is the direction of light in the resonator: clockwise or counter clockwise.</p><p>For the experiment, researchers directed light toward a pair of indirectly coupled resonators from the left (see illustration). The lightwave entered the first resonator, which was “tuned” to ensure light traveled clockwise. The light bounced around the perimeter, then exited, continuing along the fiber to the second, lower-quality resonator. </p><p>There, the light was scattered by the resonator’s imperfections and some of it began traveling counter clockwise along the perimeter. The light wave then returned to the fiber, but headed back toward the first resonator.</p><p>Critically, researchers not only used the nanoparticle in the first resonator to make the lightwaves move clockwise, they also tuned it in a way that, as the light waves propagated back and forth between resonators, a special interference pattern would form. As a result of that pattern, the light in the resonators was cancelled out, so to speak, allowing the light traveling along the fiber to eek by, rendering the system transparent. </p><p>It would be as if someone shined a light on a brick wall — no light would get through. But then another person with another flashlight shined it in the same spot and, all of a sudden, that spot in the wall became transparent.</p><p>One of the more important — and interesting — functions of EIT is its ability to create “slow light.” The speed of light is always constant, but the actual value of that speed can change based on the properties of the medium through which it moves. In a vacuum, light always travels at 300,000,000 meters per second.</p><p>With EIT, people have slowed light down to less than eight meters per second, Wang said. “That can have significant influence on the storage of light information. If light is slowed down, we have enough time to use the encoded information for optical quantum computing or optical communication.” If engineers can better control EIT, they can more reliably depend on slow light for these applications.</p><p>Manipulating EIT could also be used in the development of long distance communication. A tuning resonator can be indirectly coupled to another resonator kilometers away along the same fiber optic cable. “You could change the transmitted light down the line,” Yang said.</p><p>This could be critical for, among other things, quantum encryption.</p><p>The research team also included collaborators at Yale University, University of Chicago and the University of Southern California.<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><br/><div><div class="cstm-section"><h3>Lan Yang<br/></h3><div style="text-align: center;"> <strong><a href="/Profiles/Pages/Lan-Yang.aspx"><img src="/Profiles/PublishingImages/Yang_Lan.jpg?RenditionID=3" alt="Lan Yang" style="margin: 5px;"/></a> <br/></strong></div><ul style="text-align: left;"><li>Edwin H. & Florence G. Skinner Professor</li><li>Expertise: Photonics, optical sensing, microresonators, lasers, non-Hermitian physics, parity-time symmetry in photonics<br/></li></ul><p style="text-align: center;"> <a href="/Profiles/Pages/Lan-Yang.aspx">>> View Bio</a><br/></p></div></div><div class="cstm-section"><h3>Media Coverage<br/></h3><div> <strong>Photonics Media: </strong> <a href="">Tuned Resonators Allow Control of Electromagnetically Induced Transparency</a></div></div> <br/>Electromagnetically induced transparency (EIT) is "tuned" by two particles on the optical resonator. (Image: Yang Lab)Brandie Jefferson has ramifications for quantum computing, communications and more<p>​Method has ramifications for quantum computing, communications and more<br/></p>, Pappu, Yang among most highly-cited researchers worldwide<img alt="" src="/news/PublishingImages/Martin%20Yang%20Rohit.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>Randall Martin, Rohit Pappu and Lan Yang, all professors in the McKelvey School of Engineering at Washington University in St. Louis, have been named among the most highly-cited researchers in the sciences by the Institute for Scientific Information. </p><p>Martin, professor of energy, environmental & chemical engineering; Pappu, professor of biomedical engineering; and Yang, professor of electrical & systems engineering, were among 55 faculty from Washington University named to the list, which recognizes researchers worldwide who have demonstrated significant and broad influence reflected in their publication of multiple papers, highly cited by their peers over the course of the last decade. These papers rank in the top 1% by citations for these fields and year in Web of Science. </p><p>Washington University ranks seventh in the world for its number of highly-cited researchers. For 2019, 6,216 researchers made the <a href="">overall list</a>. <br/></p><p>Martin's research focuses on characterizing atmospheric composition to inform effective policies surrounding major environmental and public health challenges ranging from air quality to climate change. He leads a research group at the interface of satellite remote sensing and global modeling, with applications that include population exposure for health studies, top-down constraints on emissions, and analysis of processes that affect atmospheric composition. He serves as co-model scientist for a leading global atmospheric model (GEOS-Chem), leads a global fine particulate matter network (SPARTAN) to evaluate and enhance satellite-based estimates of fine particulate matter, and on multiple science teams for satellite instruments including MAIA, TEMPO and GEMS. Data from his group are relied upon for a large number of assessments, including for the OECD Regional Well-Being Index, for World Health Organization estimates of global mortality due to fine particulate matter, for the Global Burden of Disease Project to examine the risk factors affecting global public health and for a wide range of health studies.</p><p>Martin joined McKelvey Engineering in 2019 from Dalhousie University in Halifax, Nova Scotia, Canada, where he had been on the faculty since 2003. He was named professor in 2011 and Arthur B. McDonald Chair of Research Excellence in 2016. Since 2003, he also has been a research associate at the Harvard-Smithsonian Center for Astrophysics, where he also was a postdoctoral fellow. He serves on a variety of task forces, advisory boards and working groups as an expert on air quality. His professional honors include a Steacie Memorial Fellowship and selection to the Royal Society of Canada.</p><p>Pappu's research focuses on intrinsically disordered proteins (IDPs), specifically their roles in transcriptional regulation, receptor mediated cell signaling and cellular stress response. The Pappu lab has pioneered the combined use of polymer physics theories, novel homegrown computational methods, and experiments to probe the functional and phenotypic impacts of IDPs. Pappu's lab also has a large focus on neurodegeneration in Huntington's and Alzheimer's diseases. The central goal is to understand how protein aggregation and protein homeostasis pathways collude to give rise to neuronal death as a function of aging.</p><p>Pappu joined Washington University in St. Louis in 2001. He earned a doctorate in biological physics from Tufts University and completed two biophysics postdoctoral fellowships at Washington University and Johns Hopkins University Schools of Medicine. Pappu is the director of the Center for Science and Engineering of Living Systems, co-director of the Center for High-Performance Computing, and a member of the Hope Center for Neurological Disorders.</p><p>Yang is a fellow of IEEE and of The Optical Society. Her research interests include fabrication, characterization and fundamental understanding of advanced nano/micro photonic devices with outstanding optical properties or novel features for unconventional control of light flow. Her group focuses on the silicon-chip-based, ultra-high-quality micro-resonators and their applications for sensing, lasing, nonlinear optics, environmental monitoring, biomedical research and communication. Her Laboratory of Micro/Nano Photonics Research Group has demonstrated the first on-chip micro-resonator-based particle sensors that can achieve not only detection but also size measurement of single nanoparticles one by one. Different materials with tailored chemical compositions and nanostructures are used in her research to achieve advanced micro/nano photonic devices with desired properties, such as nonreciprocal light transmissions in a parity-time-symmetric optical resonator system, an all-optical analog of an electronic diode that allows current flow in one direction.</p><p>Yang joined the faculty at Washington University in 2007. In 2010, she earned a National Science Foundation CAREER Award and in 2011, she was honored by President Barack Obama with a Presidential Early Career Award for Scientists and Engineers (PECASE). The early career award is the highest honor bestowed by the United States government on science and engineering professionals in the early stages of their independent research careers.<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><br/>(From left) Randall Martin, Rohit Pappu, Lan YangBeth Miller 2019-12-09T06:00:00ZRandall Martin and Lan Yang are among the world's most highly-cited researchers in the sciences. WiFi is weak, send noise instead<img alt="" src="/news/PublishingImages/silent%20send%20noise.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>​When WiFi was designed, it was intended for high speed data communications. The Institute of Electrical and Electronics Engineers (IEEE) set the standards for communications — that’s the 802.11 protocol, a familiar number on many wireless routers.</p><p>According to the protocol, once a device is unable to send at least one megabit per second (Mbps), it is “out of range.” Even if it were physically possible to send, say, a half megabit per second, the protocol won’t allow it.</p><p>Electrical and systems engineer and computer scientist <a href="/Profiles/Pages/Neal-Patwari.aspx">Neal Patwari</a> of the McKelvey School of Engineering at Washington University in St. Louis has been working with a group using sensors to continuously collect indoor air quality data from the homes of volunteers, in a project sponsored by the National Institute of Biomedical Imaging and Bioengineering (NIBIB).</p><p>But when researchers stopped receiving data, there wasn’t a way to determine whether a sensor had been unplugged, or if something was interfering with the WiFi signal. They just needed to send a small ping, a tiny bit of data, but that was the problem — the protocol wouldn’t allow it.<br/></p><p></p><p>“We were trying to figure out, can we send lower rate data from a WiFi device even though it’s not part of the protocol, using the same hardware?” said Patwari, professor of electrical and systems engineering and of computer science and engineering.</p><p>Indeed, they found a way.</p><p>Patwari and the team presented <a href="">the results of their research</a> Oct. 22 at ACM MobiCom 2019, the 25th International Conference on Mobile Computing and Networking.</p><p>For their study regarding how indoor air quality affected asthma rates, the researchers needed lots of data from lots of homes with asthmatic children over a long period of time.</p><p>Research participants agreed to have air quality sensors in their homes. The sensors transmitted data to the researchers via WiFi, and were expected to do so for a year.</p><blockquote>“This is a problem,” Patwari said. “If you’ve ever had to set up and maintain a wireless network, you know that it requires some work every once in a while if something goes wrong.”</blockquote><p>Something will always go wrong, and, after lots of communication back and forth with participants to fix things, researchers were worried the challenges would cause participants to drop out.</p><p>Patwari experienced this frustration himself, when he put a sensor in his bedroom, across the house from his wireless router. His own student, Philip Lundrigan, also an author of the study, called when the link went down. When he went to check on the router, he had to move a basket of laundry out of the way.</p><p>Suddenly, the connection to the sensor was restored.</p><p>“It was the laundry basket,” he said, “and it was clean laundry!”</p><p>It wasn’t that the laundry had formed an impenetrable wall and the WiFi signal was stopped dead in its tracks. Rather, since the sensor was far away from the router, any small perturbation kicked the data transfer rate below 1 Mbps — the lowest transfer rate allowed by the protocol. So communication was cut off.</p><p>The situation the researchers were trying to address didn’t require that much data, though. They were just trying to find a way to figure out if the connection had been terminated, or if the sensor had been unplugged. For this purpose, instead of treating the transmitter as something that sent data, Patwari decided to consider it as something that sent noise.</p><p>Modern homes are awash in wireless noise — from computers to televisions to stereos to cell phones — the signals are everywhere. The team, led by Phil Lundrigan, assistant professor at Brigham Young University, thought they could use this to their advantage. They programmed into the WiFi sensor a series of 1s and 0s, essentially turning the signal on and off in a specific pattern. The router was able to distinguish this pattern from the surrounding wireless noise.</p><p>So even if the sensor’s data wasn’t being received, the router could pick out that pattern in the ambient noise and know that the sensor was still transmitting something.</p><p>The process isn’t entirely straightforward; some noise is louder than other noise, so the team had to devise a way to quiet some of the loudest noise in order to spot the sensor’s hidden message. Nearby signals — say, the television next to the router — were canceled out. By analyzing just a few weaker signals, it becomes much easier to pick out the pattern being sent by the sensor.</p><p>“If the access point hears this code, it says, ‘OK, I know the sensor is still alive and trying to reach me, it’s just out of range,’” Patwari said. “It’s basically sending one bit of information that says it’s alive.”</p><p>The team, which also included <a href="">Sneha K. Kasera</a>, professor at the University of Utah, eventually showed that the code could be transmitted even further than the edge of the WiFi data range — twice as far away, in fact.</p><p>“Even when the laundry basket is in the way and the link can’t send data at the 1 Mbps rate, it can still send this code,” Patwari said, “and your router then knows that the sensor is alive and transmitting. The researcher can rest easy knowing that the sensor is still collecting data, and eventually they’ll get their air quality data.”</p><p>This is just the beginning for the new innovation. It might be able to make so-called “long range” wireless protocols even longer range, according to Lundrigan, or be used on top of other wireless technology such as bluetooth or cellular.</p><p>“We can send and receive data regardless of what WiFi is doing,” Lundrigan said. “All we need is the ability to transmit energy and then receive noise measurements.”</p><SPAN ID="__publishingReusableFragment"></SPAN><p><br/></p><div><div class="cstm-section"><h3>Neal Patwari<br/></h3><div style="text-align: center;"> <strong> <a href="/Profiles/Pages/Neal-Patwari.aspx"> </a> <img src="/Profiles/PublishingImages/Neal%20Patwari_03.jpg?RenditionID=3" alt="" style="margin: 5px;"/> <br/></strong></div><ul style="text-align: left;"><li>Professor<br/></li><li>Research: The intersection of statistical signal processing and wireless networking, for improving wireless sensor networking and RF sensing. <br/></li></ul><p style="text-align: center;"> <a href="/Profiles/Pages/Neal-Patwari.aspx">>> View Bio</a><br/></p></div></div> <span> <div class="cstm-section"><h3>Media Coverage<br/></h3><div> <strong>Engadget: </strong> <a href="">BYU researchers extend WiFi range by 200 feet with a software upgrade</a></div><div> <br/> </div><div> <strong style="caret-color: #343434; color: #343434;">TechRadar: </strong><a href="">This new technology could make your Wi-Fi instantly better</a><br/></div><div> <br/> </div><div> <strong style="caret-color: #343434; color: #343434;">BYU News: </strong><a href="">Researchers create way to significantly extend Wi-Fi range for smart-home devices</a><br/></div></div></span>Brandie Jefferson wireless noise can be key to sending information, researchers find<p>​Recognizing wireless noise can be key to sending information, researchers find<br/></p>’s my car? WashU researchers to study short-term working memory<img alt="" src="/news/PublishingImages/iStock-1133618377.jpg?RenditionID=2" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>When we drive to a place and park the car, most of us walk away without giving any thought about how to find the car when we want to leave. A team of researchers at Washington University in St. Louis plans to study how and where the brain stores this type of information so that it can be retrieved when needed.</p><p>ShiNung Ching, associate professor of electrical & systems engineering in the McKelvey School of Engineering, and Lawrence Snyder, MD, PhD, professor of neuroscience at the School of Medicine, will study short-term working memory in the brain — part of a broader effort to understand the link between the dynamics and function of neural circuits — with a three-year, $1.1 million grant from the National Institutes of Health (NIH)'s National Institute of Biomedical Imaging and Bioengineering and the National Institute of Mental Health. The grant is part of the NIH's Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative aimed at revolutionizing the understanding of the human brain.</p><p>"Our goal is to take mathematical and computational theories about how resources are optimally allocated in different engineered settings, then use these ideas as a framework to think about how the brain might be allocating its resources to achieve working memory," Ching said. </p><p>Working memory is critical for normal human reasoning, and problems with it stem from normal aging as well as neuropsychiatric illnesses. A clearer understanding of how it works could lead to improvements in diagnosing and treating these illnesses.</p><p>When we do a task that requires working memory, such as parking a car or remembering a phone number, we are receiving and storing information from the periphery. We can't always anticipate when we are going to be faced with something new that we need to remember, so there is a problem of allocating resources between current and future memory needs that the brain has to solve, Ching said. </p><p>"Let's say we are observing an area of the brain that we thought was important for working memory," Ching said. "If I looked at it one minute after you parked your car, I might see some activity that suggests that it is storing the memory of your car's location. If I looked four hours later, I might see a weaker signal there. Eight hours later I may see no signal there, or something totally different, but you might nonetheless still figure out where your car is. How does the brain manage the use of those circuits? We'd like to understand how this type of prioritization is accomplished in the brain." </p><p>Ching said optimal resource allocation is also used in many engineered systems, such as power grids or smart grids, which have to determine how to distribute finite resources across a network. </p><p>"This work will take the mathematical engineering theory that we use to study those problems and see if we can use it to predict what we observe in the brain," he said. </p><p>With this information, Ching will develop models of neuronal activity in the brain, then Snyder will then examine whether the activity precited by the model is present in actual brain activity. </p><p>"We've observed that when memories first become engaged, certain neurons will become active, seemingly representing the memory, but over time, that activity will drop away, so if you look 5 or 10 seconds later, the cells appear to be doing nothing," Ching said. "Despite this, the ability to recall the memory persists. Which begs the question, why were those neurons turned 'off' and where, ultimately, in the circuit does the memory reside?"</p><SPAN ID="__publishingReusableFragment"></SPAN><br/><span> <div class="cstm-section"><h3>Collabo​rators​</h3><div style="text-align: center;"> <strong><a href="/Profiles/Pages/ShiNung-Ching.aspx"><img src="/Profiles/PublishingImages/Ching_ShiNung.jpg?RenditionID=3" class="ms-rtePosition-3" alt="" style="margin: 5px;"/>​</a> </strong></div><div style="text-align: center;"> <a href="/Profiles/Pages/ShiNung-Ching.aspx"><strong>ShiNung Ching</strong></a><br/></div><div style="text-align: center;"><div style="caret-color: #343434; color: #343434;"> <span style="font-size: 12px;">Associate Professor</span></div><div style="caret-color: #343434; color: #343434;"> <span style="font-size: 12px;">Electrical & Systems Engineering</span></div></div><div style="text-align: center;"> <span style="font-size: 12px;"> <br/></span></div><div style="text-align: center;"><div style="color: #343434; text-align: center;"> <span style="font-size: 12px;"> <a href=""> <img src="/news/PublishingImages/Pages/Where%E2%80%99s-my-car-WashU-researchers-to-study-short-term-working-memory/lawrence-snyder.jpg?RenditionID=3" alt="" style="margin: 5px;"/></a></span></div><div style="color: #343434; text-align: center;"> <strong> <a href=""> <strong>Lawrence Snyder</strong></a></strong><br/></div><div style="color: #343434; text-align: center;"> <span style="font-size: 12px;"><span style="caret-color: #343434; color: #343434; font-size: 12px;">Professor of Neuroscience</span></span></div><div style="color: #343434; text-align: center;"> <span style="font-size: 12px;"><span style="caret-color: #343434; color: #343434; font-size: 12px;">School of Medicine</span></span></div></div></div></span>Beth Miller 2019-09-25T05:00:00ZShiNung Ching and Larry Snyder at the School of Medicine plan to study how the brain allocates resources for working memory with funding from the NIH's BRAIN Initiative.

Research Areas

Applied Physics
  • Nano-photonics
  • Quantum Optics
  • Engineered Materials
  • Electrodynamics
Devices & Circuits
  • Computer Engineering
  • Integrated Circuits
  • Radiofrequency Circuits
  • Sensors
Systems Science
  • Optimization
  • Applied Mathematics
  • Control
  • Financial Engineering
Signals & Imaging
  • Computational Imaging
  • Signal Processing
  • Optical Imaging
  • Data Sciences