Faculty

professor Jelena Vučković
December 2019

Professor Jelena Vučković and team recently published "4H-silicon-carbide-on-insulator for integrated quantum and nonlinear photonics" in Nature Photonics.

Photonic chips could become the basis for light-based quantum computers that could, in theory, break codes and solve certain types of problems beyond the capabilities of any electronic computer.

In recent months Jelena has created a prototype photonic chip made of diamond. Now, however, in experiments described in Nature Photonics, she and her team demonstrate how to make a light-based chip from a material nearly as hard as diamond but far less exotic — silicon carbide.

"These are early stage but promising results with a material that is already familiar to industry," Jelena said.

Commonly used in brake pad linings, silicon carbide is a tough material that has carved out a new niche in electronics, where it is used to make chips for high-voltage, high-heat applications, such as electric car power supplies, that are too extreme for ordinary silicon chips.

Like most chip-making materials, silicon carbide is a crystal — a group of specific atoms arranged in a consistent lattice. In a silicon carbide crystal, every silicon atom is joined to four carbon atoms to form a strong, three-dimensional lattice. The stability of this lattice helps makes silicon carbide useful for high-heat applications, whether that involves dealing with friction in brake pad linings or high currents flowing through chips.

Daniil Lukin (EE PhD candidate), Constantin Dory (EE PhD candidate) and Melissa Guidry (AP PhD candidate) led the effort to make this crystal useful as a photonic chip. They removed silicon atoms at strategic locations throughout the lattice. Each vacancy in the lattice created a subatomic trap that captured a single electron from one of the surrounding carbon atoms. To make the light-based chip work, the researchers sent a stream of photons through the lattice. Whenever a photon struck a trapped electron, the collision between those two particles sent a photon spinning off at a particular energy level, or what scientists call a quantum. Interactions between photons and electrons create what scientists call a qubit, or quantum bit. A qubit is roughly analogous to the transistor in an electronic chip — the fundamental unit that makes the system work.

Many hurdles must still be overcome before photonic chips made of silicon carbide, or diamond for that matter, might become useful as the building blocks for a quantum computing system. "Hype tends to get ahead of science," Vuckovic says. But within the next five years or so, she envisions using photonic chips to send data via quantum light through fiber optic cables, making such communications more secure by making it possible to detect efforts to tap into the flow of information.

As the director of Q-FARM — short for Quantum Fundamentals, Architecture and Machines — Jelena is helping to bring together researchers from Stanford and the SLAC National Accelerator Laboratory to solve the nitty-gritty hardware and software challenges necessary to make quantum technology a reality.

"We're trying to take small, practical steps," she says, "while we try to push beyond the limits of our current understanding and discover new platforms for quantum technologies."

Excerpted from Stanford Engineering's "Can we develop computer chips that run on light?" December 2, 2019. 

 

Related Links 

 

 

 

professor Gordon Wetzstein
November 2019

Congratulations to Professor Gordon Wetzstein! He has been awarded the 2020 SPIE Early Career Achievement Award – Academic Focus – in recognition of outstanding contributions to computational imaging and display technologies. The SPIE Early Career Achievement Award recognizes significant and innovative technical contributions in the engineering or scientific fields of relevance to SPIE.

"Gordon's core research interests lie in computational imaging and photography, i.e. at the intersection of several disciplines including optics, image processing, computer vision, photography, and human perception," notes Professor Wolfgang Heidrich, the director of the King Abdullah University of Science and Technology's Visual Computing Center. "This is an emerging research area that promises to revolutionize both photography and display technologies, as well as other applications of optics through the introduction of computation, thereby enabling more robust, less expensive, and more portable optical devices. Even more importantly, it allows for completely new imaging modalities that have not been possible so far. Gordon has a clear and articulate vision of research in Computational Photography and Displays — in fact he is probably the first to really define Computational Displays as a separate sub-area with similar but distinct challenges from Computational Photography — and has been extremely active providing leadership to the community. He is an emerging star."

Please join us in congratulating Gordon for his tremendous contributions!


 

Excerpted from SPIE.org "Gordon Wetzstein: The 2020 SPIE Early Career Achievement Award – Academic Focus

SPIE.org press release "SPIE, the International Society for Optics and Photonics, Announces Its 2020 Society Awards"

 

EE Prof. H.S.- Philip Wong
October 2019

Professor H.S. Philip Wong has been awarded the IEEE Electron Devices Society J.J. Ebers Award. This is the society's highest honor recognizing outstanding technical contributions to the field of electron devices that have made a lasting impact.

The award will be presented to Philip at the 2019 International Electron Devices Meeting in December. The Jewell James Ebers Award was established in 1971 with the intention to foster progress in electron devices and to commemorate the life activities of Jewell James Ebers, whose distinguished contributions, particularly in the transistor art, shaped the understanding and technology of electron devices.

Philip is the Willard R. and Inez Kerr Bell Professor in the School of Engineering. He is professor of Electrical Engineering and affiliate faculty of Bio-X, Precourt Institute for Energy, and Wu Tsai Neurosciences Institute. Philip's present research covers a broad range of topics including carbon electronics, 2D layered materials, wireless implantable biosensors, directed self-assembly, nanoelectromechanical relays, device modeling, brain-inspired computing, and non-volatile memory devices such as phase change memory and metal oxide resistance change memory.

Please join us in congratulating Philip on this well-deserved honor!

 

Related News

image of emeritus prof Stephen E Harris
September 2019

Emeritus Professor Stephen E. Harris, the Kenneth and Barbara Oshman Professor in the School of Engineering, has been awarded the 2020 Willis E. Lamb Award for Laser Science and Quantum Optics. He will receive the award at the 2020 Physics of Quantum Electronics (PQE) Golden Jubilee - the 50th year of the annual meeting.

Stephen joined our faculty after completing his PhD (and MS) in Electrical Engineering at Stanford. He is known for his contributions to electromagnetically induced transparency (EIT)– a technique for eliminating the effect of a medium on a propagating beam of electromagnetic radiation. Additionally, he is known for his collaboration with others, producing results in many areas, including lasers, quantum electronics, atomic physics, and nonlinear optics.

Stephen E. Harris is part of Stanford's Ginzton Lab, Q-FARM, and emeritus professor of Electrical Engineering and Applied Physics.

 

Please join us in recognizing Stephen for his tremendous contributions to a variety of scientific fields!

Photo of Professor Stephen E. Harris, date unknown. source: SALLIE, Stanford's Image Exchange.

 

 

image of EE professor Eric Pop
August 2019

EE Professor Eric Pop's research was recently published in Science Advances.

Research in the Pop Lab has shown that a few layers of 2D materials can provide the same insulation as a sheet of glass 100 times thicker. "Thinner heat shields will enable engineers to make electronic devices even more compact than those we have today. We're looking at the heat in electronic devices in an entirely new way," reports Pop.

Detecting thermal vibrations
Thinking about heat as a form of sound inspired the Pop Lab researchers to borrow some principles from the physical world. "We adapted that idea by creating an insulator that used several layers of atomically thin materials instead of a thick mass of glass," said lead author Sam Vaziri, Electrical Engineering postdoc.

The team used up to four different compounds: graphene, molybdenum diselenide, molybdenum disulfide and tungsten diselenide – each three atoms thick – to create a four-layered insulator just 10 atoms deep. Despite its thinness, the insulator is effective because the atomic heat vibrations are dampened and lose much of their energy as they pass through each layer.

"As engineers, we know quite a lot about how to control electricity, and we're getting better with light, but we're just starting to understand how to manipulate the high-frequency sound that manifests itself as heat at the atomic scale," Pop said.


 

Related Links:

This research was supported by the Stanford Nanofabrication Facility, the Stanford Nano Shared Facilities, the National Science Foundation, the Semiconductor Research Corporation, the Defense Advanced Research Projects Agency, the Air Force Office of Scientific Research, the Stanford SystemX Alliance, the Knut and Alice Wallenberg Foundation, the Stanford Graduate Fellowship program and the National Institute of Standards and Technology. (ANI)

image of professor emeritus Hellman. Photo Credit: Michael Steven Walker
July 2019

Martin E. Hellman was the Heidelberg Lecturer at the 69th Lindau Nobel Laureate Meeting (#LINO19). The annual, week-long event occurs each summer on Germany's Lindau Island. Nobel Laureates are invited to the meeting, along with select young scientists. The Heidelberg Lecture is given by one of the Heidelberg Laureates, the winners of the top prizes in mathematics and computer science. Professor Hellman became a Heidelberg Laureate when he received the ACM Turing Award in 2015 for joint work with Whitfield Diffie, for making critical contributions to modern cryptography.

Martin's lecture, "The Technological Imperative for Ethical Evolution" called for scientists and laureates to accelerate the trend toward more ethical behavior. Hellman drew parallels between global and personal relationships as a foundation to build trust and security – regardless of past adversarial history. He shared 8 lessons from his own personal and professional evolution.

Martin encouraged #LINO19 attendees to revisit the Mainau Declaration of 1955 and the Mainau Declaration of 2015, thereby underscoring the efforts of prior attendees – and the responsibilities of today's attendees – to consider global and future consequences when making decisions and to appeal to decision-makers to do the same.

Hellman's Heidelberg Lecture is available online.

The 69th Lindau Nobel Laureate Meeting hosted 39 laureates and 600 young scientists from 89 countries–the highest number to date. This year's meeting was dedicated to physics. The key topics were dark matter and cosmology, laser physics and gravitational waves.


Martin E. Hellman is Professor Emeritus of Electrical Engineering at Stanford University and is affiliated with the university's Center for International Security and Cooperation (CISAC). His recent technical work has focused on rethinking national security, including bringing a risk informed framework to a potential failure of nuclear deterrence and then using that approach to find surprising ways to reduce the risk. His earlier work included co-inventing public key cryptography, the technology that underlies the secure portion of the Internet. His many honors include election to the National Academy of Engineering and receiving (jointly with his colleague Whit Diffie) the million dollar ACM Turing Award, the top prize in computer science. One of his recent projects is a book, jointly written with his wife of fifty years, "A New Map for Relationships: Creating True Love at Home & Peace on the Planet," that one reviewer said provides a "unified field theory" of peace by illuminating the connections between nuclear war, conventional war, interpersonal war, and war within our own psyches.

image of Martin Hellman, Heidelberg Lecture, Lindau Nobel Laureate Meeting 2019

Martin Hellman speaking at the Lindau Nobel Laureate Meetings. Photo credit: Julia Nimke/Lindau Nobel Laureate Meetings

image of professor Gordon Wetzstein
July 2019

Gordon Wetzstein was awarded the Presidential Early Career Awards for Scientists and Engineers (PECASE). This is the highest honor bestowed by the United States Government on science and engineering professionals in the early stages of their independent research careers.

Gordon is an assistant professor of Electrical Engineering and, by courtesy, of Computer Science. He is the leader of the Stanford Computational Imaging Lab, an interdisciplinary research group focused on advancing imaging, microscopy, and display systems.

Eleven other Stanford faculty also received the Presidential Early Career Awards for Scientists and Engineers (PECASE). Link to article below.

 

Please join us in congratulating Gordon for this recognition.


 

Related news:

image of Professor Subhasish Mitra
July 2019

In a recent QandA discussion with Stanford Engineering, EE professor Subhasish Mitra and Computer Science professor Clark Barrett, describe their recent work to secure chips before they are manufactured.

What's new when it comes to finding bugs in chips?

Designers have always tried to find logic flaws, or bugs as they are called, before chips went into manufacturing. Otherwise, hackers might exploit these flaws to hijack computers or cause malfunctions. This has been called debugging and it has never been easy. Yet we are now starting to discover a new type of chip vulnerability that is different from so-called bugs. These new weaknesses do not arise from logic flaws. Instead, hackers can figure out how to misuse a feature that has been purposely designed into a chip. There is not a flaw in the logic. But hackers might be able to pervert the logic to steal sensitive data or take over the chip.

How do your algorithms deal with traditional bugs and these new unintended weaknesses?

Let's start with the traditional bugs. We developed a technique called Symbolic Quick Error Detection — or Symbolic QED. Essentially, we use new algorithms to examine chip designs for potential logic flaws or bugs. We recently tested our algorithms on 16 processors that were already being used to help control critical automotive systems like braking and steering. Before these chips went into cars, the designers had already spent five years debugging their own processors using state-of-the-art techniques and fixing all the bugs they found. After using Symbolic QED for one month, we found every bug they'd found in 60 months — and then we found some bugs that were still in the chips. This was a validation of our approach. We think that by using Symbolic QED before a chip goes into manufacturing we'll be able to find and fix more logic flaws in less time.

Does Symbolic QED find all vulnerabilities?

Not in its current incarnation. Through collaboration with other research groups, we have modified Symbolic QED to detect new types of attacks that can come from potential misuse of seemingly innocuous features.

This is just the beginning. The processors we tested were relatively simple. Yet, as we saw, they could be perverted. Over time we will develop more sophisticated algorithms to detect and fix the most sophisticated chips, like the ones responsible for controlling navigation systems on autonomous cars. Our message is simple: As we develop more chips for more critical tasks, we'll need automated systems to find and fix all potential vulnerabilities — traditional bugs and unintended consequences — before chips go into manufacturing. Otherwise we'll always be playing catch up, trying to patch chips after hackers find the vulnerabilities.

Excerpted from "Q&A: What's new in the effort to prevent hackers from hijacking chips?"


 

Related 

 

professor Krishna Shenoy
July 2019

 

Professor Krishna Shenoy's research team has found that using statistical theory to analyze neural activity provides a faster and equally accurate process.

Krishna's team has circumvented today's painstaking process of tracking the activity of individual neurons in favor of decoding neural activity in the aggregate. Each time a neuron fires it sends an electrical signal — known as a "spike" — to the next neuron down the line. It's the sort of intercellular communication that turns a notion in the mind into muscle contraction elsewhere in the body. "Each neuron has its own electrical fingerprint and no two are identical," says Eric Trautmann, a postdoctoral researcher in Krishna's lab and first author of the paper. "We spend a lot of time isolating and studying the activity of individual neurons."

The team believes their work will ultimately lead to neural implants that use simpler electronics to track more neurons than ever before, and also do so more accurately. The key is to combine their sophisticated new sampling algorithms with small electrodes. So far, such small electrodes have only been employed to control simple devices like a computer mouse. But combining this hardware for recording brain signals with the sampling algorithms creates new possibilities. Researchers might be able to deploy a network of small electrodes through larger sections of the brain, and use the algorithms to sample a great many neurons. This could deliver enough accurate brain signal information to control a prosthetic hand capable of fast and precise motions like pitching a baseball or playing the violin.

Better yet, Trautmann said, the new electrodes, coupled with the sampling algorithms, should eventually be able to record brain activity without the many wires needed today to carry signals from the brain to whatever computer controls the prosthesis. Wireless functionality would completely untether users from bulky computers needed to decode neuronal activity today.

Krishna reports, "This study has a bit of a hopeful message in that observing activity in the brain turns out to be easier than we initially expected."

The paper, "Accurate Estimation of Neural Population Dynamics without Spike Sorting" was published in June's issue of Neuron.

Excerpted from Stanford Engineering news

Related Links

July 2019

Professor Gordon Wetzstein and team recently published their findings in Science Advances.

The researchers have created a pair of smart glasses that can automatically focus on what you're looking at. Using eye-trackers and autofocus lenses, the prototype works much like the lens of the eye, with fluid-filled lenses that bulge and thin as the field of vision changes. It also includes eye-tracking sensors that triangulate where a person is looking and determine the precise distance to the object of interest. The team did not invent these lenses or eye-trackers, but they did develop the software system that harnesses this eye-tracking data to keep the fluid-filled lenses in constant and perfect focus.

EE PhD candidate Nitish Padmanaban, said other teams had previously tried to apply autofocus lenses to presbyopia. But without guidance from the eye-tracking hardware and system software, those earlier efforts were no better than wearing traditional progressive lenses.

Gordon's team tested the prototype on 56 people with presbyopia. Test subjects said the autofocus lenses performed better and faster at reading and other tasks. Wearers also tended to prefer the autofocal glasses to the experience of progressive lenses – bulk and weight aside.

Gordon's Computational Imaging Lab is at the forefront of vision systems for VR and AR (virtual and augmented reality). It was in the course of such work that the researchers became aware of the new autofocus lenses and eye-trackers and had the insight to combine these elements to create a potentially transformative product.

Excerpted from Stanford News.

 

Related Links

 


 

 

Pages

Subscribe to RSS - Faculty