Graduate

Applied Physics/Physics Colloquium: Nuclear Geochronology and the Age of the Earth

Topic: 
Nuclear Geochronology and the Age of the Earth
Abstract / Description: 

How Old Is Earth? Because Earth formed by protracted accretion of planetestimals, asking the age of our planet is in some ways akin to asking your friends theirs and in other ways different. While your pals are unlikely to date themselves from the moment of conception, we can use U-Pb dating to pinpoint the arrival of our solar system to the formation of the first solids in primitive meteorites that condensed from the circumstellar disk at 4,567.2±0.5 million years (Ma). The timing of volatile loss from parent bodies constrains Earth to have accreted most of its mass by 4,550 Ma from impactors broadly similar in composition to meteorites but, surprisingly, of a class not yet recognized. Whereas your pals almost certainly know the day they emerged from the womb, the continuous mobility of our planet has erased any vestige of its origin. Clues remain nonetheless. Sixty years ago, Clair Patterson argued that the similarity of Pb isotopes between terrestrial rocks and meteorites established Earth's age as 4550 Ma. While his age was approximately correct, he was right for the wrong reason. Recently, two approaches have more clearly constrained an upper age bound to Earth formation; 182Hf-182W dating of core formation at ca. 4,540 Ma and 176Lu-176Hf data from terrestrial and lunar zircons as old as 4,380 Ma that require primary differentiation on both bodies to have ended by 4,510 Ma. The question of Earth's age remains of societal import as about half the population of our country believes that it is less than 10,000 years old and arose in the fashion described in Genesis. But creationists are not alone in promulgating origin myths. In the absence of any empirical evidence, the scientific community long coalesced around the view that the first (~500 Ma) of Earth history saw a continuously molten surface disrupted only by extraterrestrial impacts. Those ancient zircons noted above are seriously challenging that longstanding paradigm.

Date and Time: 
Tuesday, September 25, 2018 - 4:30pm
Venue: 
Hewlett 200

General Strong Polarization

Topic: 
General Strong Polarization
Abstract / Description: 

A martingale is a sequence of random variables that maintain their future expected value conditioned
on the past. A [0,1]-bounded martingale is said to polarize if it converges in the limit to either 0
or 1 with probability 1. A martingale is said to polarize strongly, if in t steps it is
sub-exponentially close to its limit with all but exponentially small probability. In 2008, Arikan
built a powerful class of error-correcting codes called Polar codes. The essence of his theory
associates a martingale with every invertible square matrix over a field (and a channel) and showed
that polarization of the martingale leads to a construction of codes that converge to Shannon
capacity. In 2013, Guruswami and Xia, and independently Hassani et al. showed that strong
polarization of the Arikan martingale leads to codes that converge to Shannon capacity at finite
block lengths, specifically at lengths that are inverse polynomial in the gap to capacity, thereby
resolving a major mathematical challenge associated with the attainment of Shannon capacity.

We show that a simple necessary condition for an invertible matrix to polarize over any non-trivial
channel is also sufficient for strong polarization over all symmetric channels over all prime
fields. Previously the only matrix which was known to polarize strongly was the 2×2Hadamard matrix.
In addition to the generality of our result, it also leads to arguably simpler proofs. The essence
of our proof is a local definition'' of polarization which only restricts the evolution of the
martingale in a single step, and a general theorem showing the local polarization suffices for
strong polarization.

In this talk I will introduce polarization and polar codes and, time permitting, present a full
proof of our main theorem. No prior background on polar codes will be assumed.

 

Based on joint work with Jaroslaw Blasiok, Venkatesan Guruswami, Preetum Nakkiran and Atri Rudra.

Date and Time: 
Friday, October 5, 2018 - 3:00pm
Venue: 
Gates 463A

EE Grad Student Orientation

Topic: 
Welcome Electrical Engineering Graduates
Abstract / Description: 

– Welcome to EE –

We're happy you're here!

 

 

Stanford Department of Electrical Engineering New Grad Student Orientation - 2 days of fun, exploring, learning and - of course - meeting your cohort.

Date and Time: 
Thursday, September 20, 2018 (All day) to Friday, September 21, 2018 (All day)
Tags: 

SystemX Seminar: On-chip quantum technologies based on rare-earth ion crystals

Topic: 
On-chip quantum technologies based on rare-earth ion crystals
Abstract / Description: 

Quantum technologies for computing, communication, and metrology become much more powerful if they are part of an integrated network operating at the quantum level. The first part of the this talk will introduce some of the interconnect technologies that can help to build up large quantum networks, including quantum memories and transducers. The second part of the talk will focus on demonstrations of these types of interconnects in crystals containing rare-earth ions, including on-chip technology developed at Caltech.

Date and Time: 
Thursday, October 18, 2018 - 4:30pm
Venue: 
Huang 018

SystemX Seminar: Toward Ultra-Low-Power Computing in the Era of Artificial Intelligence

Topic: 
Toward Ultra-Low-Power Computing in the Era of Artificial Intelligence
Abstract / Description: 

Computing technology has been a backbone of our society. Its importance is hard to overemphasize. Today, we again confirm its extreme importance with recent advances in artificial intelligence and deep learning. Those emerging workloads impose an unprecedented amount of arithmetic complexity and data access beyond our existing computing systems can barely handle. Particularly, mobile and embedded computing systems will face a major challenge in achieving energy-efficient computing for truly enabling intelligent systems. In this seminar, we will outline the bottlenecks of energy-efficient computing, notably the broken Dennard scaling and the memory wall problem. We will then discuss several approaches that our group has been working on, including a massively-parallel near-threshold processor, circuits and architectures to tolerate variability, active leakage suppression, integrated DCDC converters and voltage regulators for per-core DVFS, in-memory computing hardware, hybrid analog-digital computing, and a deep learning algorithm that reduces communication to off-chip memory. We will introduce several test-chip prototypes and their measurement results. 

Date and Time: 
Thursday, October 11, 2018 - 4:30pm
Venue: 
Huang 018

SystemX Seminar: Quantum Computing on Near Term Hardware

Topic: 
Quantum Computing on Near Term Hardware
Abstract / Description: 

Within the last few years, quantum computing has moved from an academic field of study to a blossoming industry with a healthy ecosystem comprised of startups as well as research groups at large corporations. In this talk we will give a general introduction to this topic, describe a selection of the currently competing hardware platforms and demonstrate how to program a near term quantum computer.

Date and Time: 
Thursday, October 4, 2018 - 4:30pm
Venue: 
Huang 018

SystemX Seminar: Wireless Electric Vehicle Charging Overview

Topic: 
Wireless Electric Vehicle Charging Overview
Abstract / Description: 

The talk will provide an overview of Wireless Electric Vehicle Charging (WEVC) technology and the market. It will include a discussion of the system and its high-level components, safety and emissions considerations and standards work. Current state of the art systems both in late stage and early stage development will be discussed, including dynamic wireless charging. It will also include a brief overview on Formula E, the electric racing series.

Date and Time: 
Thursday, September 27, 2018 - 4:30pm
Venue: 
Huang 018

US-ATMC (EE402) Seminar

Topic: 
Fall '18 theme: AI in Smart Physical Systems: Will Asia Lead the Way?
Abstract / Description: 

The upcoming series features presentations by distinguished guest speakers from industry about practical innovations from Asia related to the use of artificial intelligence in smart physical systems, e.g. smart buildings, autonomous vehicles, drone fleets, supply chain management, smart manufacturing, etc

Date and Time: 
Thursday, December 6, 2018 - 4:30pm
Venue: 
Skilling Auditorium, 494 Lomita Mall

US-ATMC (EE402) Seminar

Topic: 
Fall '18 theme: AI in Smart Physical Systems: Will Asia Lead the Way?
Abstract / Description: 

The upcoming series features presentations by distinguished guest speakers from industry about practical innovations from Asia related to the use of artificial intelligence in smart physical systems, e.g. smart buildings, autonomous vehicles, drone fleets, supply chain management, smart manufacturing, etc

Date and Time: 
Thursday, November 29, 2018 - 4:30pm
Venue: 
Skilling Auditorium, 494 Lomita Mall

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