In their recent paper, Wireless NoC for VFI-enabled multicore chip design: performance evaluation and design trade-offs, researchers from Carnegie Mellon's Department of Electrical and Computer Engineering and Washington State University identify a new approach for enabling energy-efficient multicore systems. Much like bypassing road congestion when traveling long distances, by using wireless on-chip communication between individually controllable clusters, researchers were able to provide an efficient communication backbone, which can be tailored for large scale multicore systems. This paper presents a platform that is poised to save significant energy with little or no performance penalty. The article is the featured IEEE Transactions on Computers paper for the month of April. As the number of cores packed into a single chip rises, scalable power management strategies are needed to keep power under prescribed limits. Voltage frequency islands, or VFIs, have long been used to enable such strategies. In VFI-based designs, the system is partitioned into islands with individually adjustable voltage and frequencies so as to reduce the power within allowable performance penalties. However, while enabling significant power savings, a main challenge of VFI-based designs is the on-chip communication cost which negatively impacts application performance. Indeed, mixed voltage/frequency interfaces must be used for inter-VFI communication, thereby increasing communication delay. This paper presents two innovative solutions, the first of which is through the VFI clustering methodology. A hybrid VFI clustering that combines both per-VFI utilization and inter-VFI communication enables minimal inter-VFI communication without greatly increasing the inter-cluster utilization variation. Secondly, researchers utilized a small-world wireless Network on Chip or mSWNoC to enable fast and energy efficient on-chip communication. The mSWNoC exploits small-world connectivity for reducing communication costs through wireless long-range short cuts between VFIs. The wireless small-world connectivity is able to mitigate most of the performance penalties introduced by VFIs. Furthermore, VFI-based multicore systems with mSWNoC communication are shown to be significantly better in energy efficiency compared to classic systems using wired on-chip networks (e.g. mSWNoC improves the energy dissipation by 40% and the energy-delay product by 52% compared to a wireline mesh on common PERSEC and SPLASH-2 benchmarks)
News Article | April 21, 2016
Phone calls and text messages reach you wherever you are because your phone has a unique identifying number that sets you apart from everybody else on the network. Researchers at the Georgia Institute of Technology are using a similar principle to track cells being sorted on microfluidic chips. The technique uses a simple circuit pattern with just three electrodes to assign a unique seven-bit digital identification number to each cell passing through the channels on the microfluidic chip. The new technique also captures information about the sizes of the cells, and how fast they are moving. That identification and information could allow automated counting and analysis of the cells being sorted. The research, reported in the journal Lab on a Chip, could provide the electronic intelligence that might one day allow inexpensive labs on a chip to conduct sophisticated medical testing outside the confines of hospitals and clinics. The technology can track cells with better than 90 percent accuracy in a four-channel chip. "We are digitizing information about the sorting done on a microfluidic chip," explained Fatih Sarioglu, an assistant professor in Georgia Tech's School of Electrical and Computer Engineering. "By combining microfluidics, electronics and telecommunications principles, we believe this will help address a significant challenge on the output side of lab-on-a-chip technology." Microfluidic chips use the unique biophysical or biochemical properties of cells and viruses to separate them. For instance, antigens can be used to select bacteria or cancer cells and route them into separate channels. But to obtain information about the results of the sorting, those cells must now be counted using optical methods. The new technique, dubbed microfluidic CODES, adds a grid of micron-scale electrical circuitry beneath the microfluidic chip. Current flowing through the circuitry creates an electrical field in the microfluidic channels above the grid. When a cell passes through one of the microfluidic channels, it creates an impedance change in the circuitry that signals the cell's passage and provides information about the cell's location, size and the speed at which it is moving through the channel. This impedance change has been used for many years to detect the presence of cells in a fluid, and is the basis for the Coulter Counter which allowed blood counts to be done quickly and reliably. But the microfluidic CODES technique goes beyond counting. The positive and negative charges from the intermingled electrical circuits create a unique identifying digital signal as each cell passes by, and that sequence of ones and zeroes is attached to information about the impedance change. The unique identifying signals from multiple cells can be separated and read by a computer, allowing scientists to track not only the properties of the cells, but also how many cells have passed through each channel. "By judiciously aligning the grid pattern, we can generate the codes at the locations we choose when the cells pass by," Sarioglu explained. "By measuring the current conduction in the whole system, we can identify when a cell passes by each location." Because the cells sorted into each channel of a microfluidic chip have certain characteristics in common, the technique would allow the automated detection of cancer cells, bacteria or even viruses in a fluid sample. Sarioglu and his students have demonstrated that they can track more than a thousand ovarian cancer cells with an accuracy rate of better than 90 percent. The underlying principle for the cell identification is called code division multiple access (CDMA), and it's essential for helping cellular networks separate the signals from each user. The microfluidic channels are fabricated from a plastic material using soft lithographic techniques. The electrical pattern is fabricated separately on a glass substrate, then aligned with the plastic chip "We have created an electronic sensor without any active components," Sarioglu said. "It's just a layer of metal, cleverly patterned. The cells and the metallic layer work together to generate digital signals in the same way that cellular telephone networks keep track of each caller's identity. We are creating the equivalent of a cellphone network on a microfluidic chip." The next step in the research will be to combine the electronic sensor with a microfluidic chip able to actively sort cells. Beyond cancer cells, bacteria and viruses, such a system could also sort and analyze inorganic particles. The computing requirements of the system would be minimal, requiring no more than the processor power of smartphones that already handle decoding of CDMA signals. The proof-of-principle device contains just four channels, but Sarioglu believes the design could easily be scaled up to include many more channels. "This is like putting a USB port on a microfluidic chip," he explained. "Our technique could turn all of the microfluidic manipulations that are happening on the chip into quantitative data related to diagnostic measurements. Ultimately, the researchers hope to create inexpensive chips that could be used for sophisticated diagnostic testing in physician offices or remote locations. Chips might be contained on cartridges that would automate the testing process. "It will be very exciting to scale this up, and I think that will open up the possibility for many different assays to become accessible electronically," Sarioglu said. "Decentralizing health care is an important trend, and our technology might one day allow many kinds of diagnostic tests to be done beyond hospitals and large medical facilities."
The new mass-spectral imaging system is the first of its kind in the world and its applications are just beginning to surface, said Carmen Menoni, a University Distinguished Professor in the Department of Electrical and Computer Engineering. A special issue of Optics and Photonics News last month highlights the CSU research among "the most exciting peer-reviewed optics research to have emerged over the past 12 months." Editors identified the imaging device among global "breakthroughs of interest to the optics community." Menoni's group, in collaboration with an interdisciplinary group of faculty, devised and built the instrument with help from students. She found a partner in CSU's renowned Mycobacteria Research Laboratories, which seek new treatments for the global scourge of tuberculosis. The partners described the system in a paper published earlier this year in Nature Communications. Dean Crick, a professor who researches tuberculosis, collaborated with Menoni to refine the mass spectrometer imaging system. He said the instrument will allow him to examine cells at a level 1,000 times smaller than that of a human hair - about 100 times more detailed than was earlier possible. This will give researchers the ability to observe how well experimental drugs penetrate and are processed by cells as new medications are developed to combat disease. Crick's primary research interest is tuberculosis, an infectious respiratory disease that contributes to an estimated 1.5 million deaths around the world each year. "We've developed a much more refined instrument," Crick said. "It's like going from using a dull knife to using a scalpel. You could soak a cell in a new drug and see how it's absorbed, how quickly, and how it affects the cell's chemistry." The earlier generation of laser-based mass-spectral imaging could identify the chemical composition of a cell and could map its surface in two dimensions at the microscale, but could not chart cellular anatomy at the more detailed nanoscale and in 3-D, Crick said. In addition to observing how cells respond to new drugs, he said, researchers could use the technology to identify the sources of pathogens propagated for bioterrorism. The instrument might also be used to investigate new ways to overcome antibiotic resistance among patients with surgical implants. "You might be able to customize treatments for specific cell types in specific conditions," Crick said. The CSU instrument would cover the average dining room table. Its central features are mass-spectral imaging technology and an extreme ultraviolet laser. Jorge Rocca, also a University Distinguished Professor in the Department of Electrical and Computer Engineering, created the laser attached to the spectrometer. Its beam is invisible to the human eye and is generated by an electrical current 20,000 times stronger than that of regular fluorescent tubes in ceiling lights, resulting in a tiny stream of plasma that is very hot and dense. The plasma acts as a gain medium for generating extreme ultraviolet laser pulses. The laser may be focused to shoot into a cell sample; each time the laser drills a tiny hole, miniscule charged particles, or ions, evaporate from the cell surface. These ions then may be separated and identified, allowing scientists to determine chemical composition. The microscopic shrapnel ejected from each hole allows scientists to chart the anatomy of a cell piece by piece, in three dimensions, at a scale never seen before, the scientists said. The project was funded with $1 million from the National Institutes of Health as part of an award to the Rocky Mountain Regional Center of Excellence for Biodefense and Emerging Infectious Disease Research. The optical equipment that focuses the laser beam was created by the Center for X-Ray Optics at the Lawrence Berkeley National Laboratory in Berkeley, Calif. The CSU system recently received support for system engineering design from Siemens. The company gave the CSU team an academic grant for its NX software package, including 30 seat licenses, valued at $37 million. Other CSU faculty involved in the project include Feng Dong and Elliot Bernstein from the Department of Chemistry. The lead author on the paper published in Nature Communications is Ilya Kuznetsov, a CSU doctoral student in Electrical and Computer Engineering. "The whole system was built by students and post-docs," Menoni said. "This is something we pride ourselves on, that the students get an interdisciplinary experience. Having access to design software such as the Siemens NX package is critical for creating these instruments and for training students." Key to the project has been collaboration among scientists who build high-tech devices and those who use them to solve global problems. "It's been very interesting learning how to communicate with engineers," Crick said. "We don't think alike. They understand the biology about as well as I understand the engineering. But over the years we've learned how to talk to each other, which is nice. I can see the need for the instrument, but I have no idea how to build it. They do." At one end of the instrument is a special laser created in an argon gas-filled tube when a pulse of 60 kilovolts is discharged. "It's like a lightning strike in a nanosecond," said Carmen Menoni, University Distinguished Professor in the Department of Electrical and Computer Engineering. The laser is guided through chambers using mirrors and special lenses that focus it down to a diameter of less than 100 nanometers. In a chamber at the far side of the spectrometer, the laser hits a sample cell placed with the aid of a microscope. "When you're trying to hit a single bacterium with a laser, it's tricky. You have to aim well," said Dean Crick, a CSU professor in the Department of Microbiology, Immunology and Pathology. Once the laser drills a miniscule hole in the cell, charged ions emitted after the tiny explosion are drawn into a side tube using electrostatic fields. The larger mass the charged particle has, the slower it moves down the tube; the time it takes an ion to reach a detector gives scientists information about its mass. "It's like you have a sports car and a big truck," said Ilya Kuznetsov, a doctoral student in Electrical and Computer Engineering. "Imagine you put the same motor in both—they will move at different speeds. And the more you allow them to go, the more they separate. That's why our tube is so long, to allow for that differentiation." A set of special pumps creates high vacuum that sucks all air from the tube, to remove any foreign particles the sample might collide with and to ensure equally smooth sailing for all the ions. "If you want to have a car race, you need to remove all traffic from the roads," Kuznetsov explained. By keeping the charge and amount of energy applied to each particle consistent, the mass becomes the key signature that provides researchers with every ion's chemical identity. A computer program developed in-house generates the data in a color spectrum of masses, which is then used to create a kind of topographical cell composition map. Explore further: Research team refrigerates liquids with a laser for the first time
Home > Press > Light and matter merge in quantum coupling: Rice University physicists probe photon-electron interactions in vacuum cavity experiments Abstract: Where light and matter intersect, the world illuminates. Where light and matter interact so strongly that they become one, they illuminate a world of new physics, according to Rice University scientists. Rice physicists are closing in on a way to create a new condensed matter state in which all the electrons in a material act as one by manipulating them with light and a magnetic field. The effect made possible by a custom-built, finely tuned cavity for terahertz radiation shows one of the strongest light-matter coupling phenomena ever observed. The work by Rice physicist Junichiro Kono and his colleagues is described in Nature Physics. It could help advance technologies like quantum computers and communications by revealing new phenomena to those who study cavity quantum electrodynamics and condensed matter physics, Kono said. Condensed matter in the general sense is anything solid or liquid, but condensed matter physicists study forms that are much more esoteric, like Bose-Einstein condensates. A Rice team was one of the first to make a Bose-Einstein condensate in 1995 when it prompted atoms to form a gas at ultracold temperatures in which all the atoms lose their individual identities and behave as a single unit. The Kono team is working toward something similar, but with electrons that are strongly coupled, or "dressed," with light. Qi Zhang, a former graduate student in Kono's group and lead author of the paper, designed and constructed an extremely high-quality cavity to contain an ultrathin layer of gallium arsenide, a material they've used to study superfluorescence. By tuning the material with a magnetic field to resonate with a certain state of light in the cavity, they prompted the formation of polaritons that act in a collective manner. "This is a nonlinear optical study of a two-dimensional electronic material," said Zhang, who based his Ph.D. thesis on the work. "When you use light to probe a material's electronic structure, you're usually looking for light absorption or reflection or scattering to see what's happening in the material. That light is just a weak probe and the process is called linear optics. "Nonlinear optics means light does something to the material," he said. "Light is not a small perturbation anymore; it couples strongly with the material. As you change the coupling strength, things change in the material. What we're doing is the extreme case of nonlinear optics, where the light and matter are coupled so strongly that we don't have light and matter anymore. We have something in between, called a polariton." The researchers employed a parameter known as vacuum Rabi splitting to measure the strength of the light-matter coupling. "In more than 99 percent of previous studies of light-matter coupling in cavities, this value is a negligibly small fraction of the photon energy of the light used," said Xinwei Li, a co-author and graduate student in Kono's group. "In our study, vacuum Rabi splitting is as large as 10 percent of the photon energy. That puts us in the so-called ultrastrong coupling regime. "This is an important regime because, eventually, if the vacuum Rabi splitting becomes larger than the photon energy, the matter goes into a new ground state. That means we can induce a phase transition, which is an important element in condensed matter physics," he said. Phase transitions are transitions between states of matter, like ice to water to vapor. The specific transition Kono's team is looking for is the superradiant phase transition in which the polaritons go into an ordered state with macroscopic coherence. Kono said the amount of terahertz light put into the cavity is very weak. "What we depend on is the vacuum fluctuation. Vacuum, in a classical sense, is an empty space. There's nothing. But in a quantum sense, a vacuum is full of fluctuating photons, having so-called zero-point energy. These vacuum photons are actually what we are using to resonantly excite electrons in our cavity. "This general subject is what's known as cavity quantum electrodynamics (QED)," Kono said. "In cavity QED, the cavity enhances the light so that matter in the cavity resonantly interacts with the vacuum field. What is unique about solid-state cavity QED is that the light typically interacts with this huge number of electrons, which behave like a single gigantic atom." He said solid-state cavity QED is also key for applications that involve quantum information processing, like quantum computers. "The light-matter interface is important because that's where so-called light-matter entanglement occurs. That way, the quantum information of matter can be transferred to light and light can be sent somewhere. "For improving the utility of cavity QED in quantum information, the stronger the light-matter coupling, the better, and it has to use a scalable, solid-state system instead of atomic or molecular systems," he said. "That's what we've achieved here." The high-quality gallium arsenide materials used in the study were synthesized via molecular beam epitaxy by John Reno of Sandia National Laboratories and John Watson and Michael Manfra of Purdue University, all co-authors of the paper. Weil Pan of Sandia National Laboratories and Rice graduate student Minhan Lou, who participated in sample preparation and transport and terahertz measurements, are also co-authors. Zhang is now the Alexei Abrikosov Postdoctoral Fellow at Argonne National Laboratory. Kono is a Rice professor of electrical and computer engineering, of physics and astronomy and of materials science and nanoengineering. Li received a "Best First-Year Research Award" from Rice's Department of Electrical and Computer Engineering for his work on the project. ### The research was supported by the National Science Foundation, U.S. Department of Energy, Lockheed Martin Corp. and the W.M. Keck Foundation. About Rice University Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. 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From Data Centers to Wireless Datacenter on Chip (WiDoCs). Credit: Carnegie Mellon University Electrical and Computer Engineering Diana Marculescu and Radu Marculescu have been awarded an NSF grant to develop a new paradigm for Big Data computing. Specifically, this project focuses on a new Datacenter-on-a-Chip (DoC) design consisting of thousands of cores that can run compute- and data-intensive applications more efficiently compared to existing platforms. Currently, data centers (DC) and high performance computing clusters are dominated by power, thermal, and area constraints. They occupy large spaces and necessitate sophisticated cooling mechanisms to sustain the required performance levels. The proposed new DoC design consists of thousands of cores that communicate via a new communication infrastructure, while provisioning the system resources for the necessary power, performance, and thermal trade-offs (Fig.1). From an intellectual perspective, this approach lies squarely at the intersection of two major trends in integrated systems design, namely low power and communication centric design. "There are three goals in this project," explains Radu Marculescu. "We want to design small-world wireless architecture as a communication backbone for many core-enabled Wireless Datacenter on Chip (WiDoC), while establishing physical layer design methods for highly-integrated 3-D WiDoC suitable for low latency data communication. We hope to evaluate latency-power-thermal trade-offs for the proposed WiDoC platform by considering relevant big data applications." The unique proposed research brings together highly novel and interdisciplinary concepts from network-on-chip (NoC), wireless and complex networks, communication circuits, and optimization techniques aimed at single chip solutions for achieving data center-scale performance. At the same time, this work will help to establish an interdisciplinary research-based curriculum for high performance many-core system design meant to increase the number of students attracted to this area of engineering. "Our research will impact numerous areas," says Diana Marculescu. "Big data applications like social computing, life sciences, networking, and entertainment will benefit immensely from this new design paradigm that aims at achieving server-scale performance from hand-held devices." This is a joint project between Carnegie Mellon University and Washington State University. Preliminary results based on this work will be presented at the 2016 edition of Embedded Systems Week.