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Seminar

DeCenter Seminar - Designing Blockchain Systems for Real-World Networks

Date and Time
Tuesday, March 21, 2023 - 11:30am to 12:30pm
Location
103 Maeder Hall
Type
Seminar
Speaker
Lei Yang, from MIT
Host
Andrés Monroy-Hernández

Lei Yang
The past decade saw renewed interest in decentralized systems, fueled by their promises to harden vital services in our society against intentional and unintentional corruption, and to equalize access to these services. A key enabler of modern decentralized applications are blockchains, which are fault-tolerant distributed systems operated by trust-minimized entities across the world. Blockchains are inherently network systems, but existing designs critically overlook the dynamics of real-world networks such as variability and congestion. In this talk, I will explain how this mismatch leads to performance bottlenecks, security vulnerabilities, and operational challenges that are hindering the goal of decentralization for blockchains. I will then discuss two techniques to close this gap: (1) DispersedLedger, a network-aware decomposition of Byzantine-fault-tolerant state machine replication (BFT) protocols, which enables blockchains to robustly achieve high throughput and low latency in variable networks like the Internet; (2) a unified framework to analyze and secure longest-chain BFT protocols under bandwidth constraints. These techniques use tools from distributed systems, security, and computer networks, and have wide-ranging implications for the entire blockchain system stack

Bio: Lei Yang is a PhD candidate at MIT advised by Prof. Mohammad Alizadeh. His research focuses on the intersection of networks and blockchains, using tools from distributed systems, computer networks, and security. A theme of his works is to examine the explicit and implicit assumptions that existing blockchain systems make of the network, and design novel techniques to bridge the gap between the assumptions and the reality. His works are backed by high-performance system implementations and end-to-end evaluations in real-world scenarios.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

DeCenter Seminar - Transparency and Security via Algorithmic Economics

Date and Time
Tuesday, April 11, 2023 - 10:30am to 11:30am
Location
Computer Science Small Auditorium (Room 105)
Type
Seminar
Host
Matt Weinberg

Matheus Venturyne Xavier Ferreira
Traditionally one assumes a regulator (or potential future consumers) would punish a platform for deviating from its promised specification. However, this is not always possible, even with publicly available data. For example, auctions are the main building block of how we transact on eBay or how Google sells advertising; however, it is impossible to know whether or not a self-interested auctioneer is also bidding in their auction with a fake identity. In this light, algorithmic economics provides a new perspective on designing secure systems because, in many real-world applications, adversaries are not intentionally malicious but rather rational and economically driven. First, I will overview the challenges of designing Internet auctions when auctioneers are not trusted and show a cryptographic auction that overcomes known impossibility results from economic theory. Beyond auctions, distributed systems like blockchains aim to enable more transparent platforms. In the second part, I will overview my contributions toward the design of incentive-compatible sustainable blockchains and show applications to the design of more transparent and secure platforms.

Bio: Matheus Venturyne Xavier Ferreira is a Postdoctoral Fellow in Computer Science at Harvard John A. Paulson School of Engineering and Applied Sciences. He holds a Ph.D. (2022) and a MA (2018) in Computer Science from Princeton University and a BS in Computer Engineering (2016) from the Federal University of Itajubá. His primary research interests are in security, algorithmic economics, and cryptography. His honors include a CNS Prize for Excellence in Networking from UC, San Diego (2014), a Dean’s Grand from Princeton Graduate School (2016-2021), a LATinE Fellowship (2020) from Purdue College of Engineering, and an Award for Excellence from Princeton School of Engineering (2020). Matheus is from Itabira, which is known as the Brazilian capital of poetry.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

Quantum Seminar - A Hybrid Computing Ecosystem for Practical Quantum Advantage

Date and Time
Thursday, April 6, 2023 - 4:30pm to 5:30pm
Location
Engineering Quadrangle B205
Type
Seminar
Speaker
Gokul Subramanian Ravi, from the University of Chicago
Host
Hakan Türeci

Gokul Subramanian Ravi
As quantum computing transforms from lab curiosity to technical reality, we must unlock its full potential to enable meaningful benefits on real-world applications with imperfect quantum technology. Achieving this vision requires computer architects to play a key role, leveraging classical computing principles to build and facilitate a hybrid computing ecosystem for practical quantum advantage.

First, I will introduce my four research thrusts toward building this hybrid ecosystem: Classical Application Transformation, Adaptive Noise Mitigation, Scalable Error Correction and Efficient Resource Management.

Second, from the Classical Application Transformation thrust, I will present "CAFQA: A classical simulation bootstrap for variational quantum algorithms", which enables accurate classical initialization for VQAs by searching efficiently through the classically simulable portion of the quantum space with Bayesian Optimization. CAFQA recovers as much as 99.99% of the accuracy lost in prior state-of-the-art classical initialization, with mean improvements of 56x.

Third, from the Scalable Error Correction thrust, I will present "Clique: Better than worst-case decoding for quantum error correction", which proposes the Clique QEC decoder for cryogenic quantum systems. Clique is a lightweight cryo-decoder for decoding and correcting common trivial errors, so that only the rare complex errors are handled outside the cryo-refrigerator. Clique eliminates 90-99+% of the cryo-refrigerator I/O decoding bandwidth, while supporting more than a million physical qubits.

Finally, I will conclude with an overview of other prior and ongoing work, along with my future research vision toward practical quantum advantage.

Bio: Gokul Subramanian Ravi is a 2020 NSF CI Fellows postdoctoral scholar at the University of Chicago, mentored by Prof. Fred Chong. His research targets quantum computing architecture and systems, primarily on themes at the intersection of quantum and classical computing. He received his PhD in computer architecture from UW-Madison in 2020 and was advised by Prof. Mikko Lipasti. He was awarded the 2020 Best ECE Dissertation Award from UW-Madison and named a 2019 Rising Star in Computer Architecture. His quantum and classical computing research have resulted in publications at top computer architecture, systems, and engineering venues (such as ASPLOS, ISCA, MICRO, HPCA, TACO, ISLPED, QCE, IISWC), as well as two granted and three pending patents. His co-authored work was recognized as the Best Paper at HPCA 2022 and as a 2023 IEEE Micro Top Picks Honorable Mention.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

Quantum Seminar - Tailoring Quantum Error Correction for Structured Noise

Date and Time
Wednesday, March 22, 2023 - 4:30pm to 5:30pm
Location
Computer Science Small Auditorium (Room 105)
Type
Seminar
Speaker
Jahan Claes, from Yale University
Host
Jeff Thompson

Jahan Claes
Large-scale quantum computers will require error correction in order to reliably perform computations. However, the hardware overhead for error correction remains dauntingly large, with each logical qubit potentially requiring thousands of physical qubits for reliable operation. One promising approach to reducing the overheads of error correction is to tailor quantum error correcting codes to the dominant noise in the qubit hardware.

In this talk, I’ll present recent work on tailoring measurement-based quantum computing for photonic quantum computers. Building a quantum computer out of photons allows one to avoid many sources of error, but introduces a new photonic error known as“fusion failure,” which occurs at a very high rate. Existing schemes for error correction can tolerate a fusion failure rate of 24%, but experimentally feasible fusions fail at least 25% of the time. We introduce new tailored designs for error correction in photonic quantum computers that allows for the correction of a surprisingly high rate of fusion failures; in one of our schemes, we can tolerate a failure rate of over 34%. This surpasses a key barrier in building a photonic quantum computer.

Bio: Jahan Claes received his PhD from the University of Illinois at Urbana Champaign in condensed matter physics. As a graduate student, he was a Feynman Intern at NASA’s Quantum Artificial Intelligence Lab, where he researched methods for characterizing errors in experimental quantum computers, as well as a Quantum Algorithms Intern at QC Ware, where he researched quantum optimization algorithms. Jahan is currently the YQI Postdoctoral Fellow at Yale University, where he researches tailored error correction and error characterization for quantum computers.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

Quantum Seminar - Quantum Computational Advantage: Recent Progress and Next Steps

Date and Time
Monday, March 20, 2023 - 4:30pm to 5:30pm
Location
Engineering Quadrangle B205
Type
Seminar
Speaker
Xun Gao, from Harvard University
Host
Ran Raz

Xun Gao
This talk is motivated by the question: why do we put so much effort and investment into quantum computing? A short answer is that we expect the existence of quantum computational advantage, especially for practical problems. In 2019, Google claimed to achieve quantum advantage, also known as quantum supremacy. In the first part of this talk, we question this claim and reveal fundamental limitations in their approach by constructing efficient classical algorithms to solve the same task.

Due to the shortcomings of current protocols, it is imperative to design the next generation of experiments with a more solid theoretical foundation, and ideally to find quantum advantage on problems with practical applications. In the second part of this talk, we propose a new neural sequence quantum model for language translation with better expressive power than any reasonable classical neural network. This protocol is based on quantum contextuality. Finally, I will briefly mention another potential approach: quantum algorithms for combinatorial optimization problem.

Bio: Xun Gao is a postdoc at Harvard (MPHQ fellowship). Xun received his PhD from Tsinghua University. His work explores the power and applications of near-term quantum computers, including quantum machine learning, quantum optimization algorithm and simulation of noisy quantum devices.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

Quantum Seminar - Error Correction in Quantum Computers and Beyond

Date and Time
Monday, March 13, 2023 - 4:30pm to 5:30pm
Location
Friend Center 004
Type
Seminar
Speaker
Aleksander Kubica, from Amazon Web Services Center for Quantum Computing
Host
Ran Raz

Aleksander Kubica
Quantum computers introduce a radically new paradigm of information processing and revolutionize our thinking about the world. However, designing and building quantum computers that operate properly even when some of their components malfunction and cause errors is a heroic endeavor. In this talk, I will explain how quantum error correction and the theory of fault tolerance are indispensable to achieve this task. I will also discuss the profound impact of quantum error correction on our understanding of nature, ranging from new insights into quantum many-body physics to fundamental limitations on sensing and computation

Bio: Aleksander Kubica is a research scientist at the Amazon Web Services Center for Quantum Computing in Pasadena, CA, USA. Aleksander received his Ph.D. from the California Institute of Technology under the supervision of John Preskill. He was a postdoctoral fellow at Perimeter Institute for Theoretical Physics and the Institute for Quantum Computing, University of Waterloo, Canada. His work explores various aspects of quantum technologies, including quantum computation, quantum error correction and quantum metrology. Aleksander is also excited about the intersection of quantum information science and quantum many-body physics.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

Quantum Seminar - An Architect’s Perspective on Quantum Computer Scaling: Why, What, and How?

Date and Time
Thursday, March 23, 2023 - 4:30pm to 5:30pm
Location
Engineering Quadrangle B205
Type
Seminar
Host
Andrew Houck

Kailin Smith
Quantum computation has potential to solve problems that are out of reach for today’s classical computers. Many of the proposed applications for quantum computers (QCs), such as those in chemistry, material science, and optimization, are capable of substantial human impact. However, the full promise of quantum will only be realized if better qubits and QCs emerge that are capable of large-scale computation. The roadmap to QC scaling does not only contain a single path but many that run in parallel. In addition to pursuing devices with more qubits, quantum researchers must 1) co-design software that pushes the frontier of existing machines and 2) build models that guide future QC design toward optimized performance. In this talk, I discuss the why, what, and how involved with scaling today’s QCs. First, I motivate the pursuit of quantum computing and introduce fundamental concepts. Next, I present a case study that explores optimized quantum circuit compilation, reducing decoherence via circuit slack. I show how quantum algorithms can adapt to the unique characteristics of today’s QCs through optimized gate scheduling, leading to significant improvements in success during runtime. In the third part of this talk, hardware challenges that restrict the number qubits on-chip are highlighted. With a focus on fixed-frequency transmon QCs, I explore the viability of modular architectures to scale quantum devices, presenting promising results in terms of yield, gate performance, and application-based analysis. Finally, an outlook is given on future directions in QC software and hardware co-design that aim to accelerate progress toward achieving practical quantum machines.

Bio: Kaitlin is a quantum software manager at Super.tech, a software division of Infleqtion. From 2020-2022, she was an IBM and Chicago Quantum Exchange Postdoctoral Scholar in the University of Chicago’s Department of Computer Science, advised by Prof. Fred Chong. Kaitlin is a co-author of the 2022 IEEE International Symposium on High-Performance Computer Architecture (HPCA) Best Paper, named a 2021 MIT EECS Rising Star, and the recipient of the 2021 IEEE Computer Society Technical Committee on Multiple Valued Logic (TC-MVL) Kenneth C. Smith Early Career Award in Microelectronics.


To request accommodations for a disability please contact Andrea Mameniskis, amamenis@princeton.edu, at least one week prior to the event.

DeCenter Seminar: Andrew Hall on Decentralizing Governance for Online Platforms

Date and Time
Friday, March 3, 2023 - 12:30pm to 1:30pm
Location
Computer Science Small Auditorium (Room 105)
Type
Seminar
Speaker
Andrew Hall, from Stanford University

This talk provides an overview of potential motivations for decentralizing online platforms and explores how the governance of these platforms might work. I will present data from an ongoing research project on the governance of DAOs, explain the central challenges to decentralized governance, and propose potential solutions and directions for new research. 

Andrew Hall

Andrew Hall is a Professor of Political Economy at the Stanford Graduate School of Business, with a joint appointment in the Stanford University Political Science Department. He is a senior fellow at the Stanford Institute for Economic Policy Research, and for the 2022–2023 academic year, a senior fellow by courtesy at the Hoover Institution. Hall’s research group combines large-scale quantitative datasets with methods from economics and computer science to study democratic systems of governance. Along with his academic research, Hall works at the intersection of tech and society, advising tech companies, startups, blockchain protocols, and others on how to make better and more socially legitimate decisions, products, and policies. 

Members of the public (without Princeton affiliation) who wish to attend must register. PUID holders do not need to register. Make sure you sign up for the email list to learn about DeCenter activities.

DeCenter Seminar Series: Correctness Conditions for Cross-chain Transactions

Date and Time
Thursday, November 3, 2022 - 12:30pm to 1:30pm
Location
Computer Science Small Auditorium (Room 105)
Type
Seminar
Speaker
Maurice Herlihy, from Brown University
Host
Jaswinder Pal Singh

Join us for the second DeCenter seminar series event featuring Maurice Herligy, professor of computer science at Brown University. Lunch will be available beginning at noon. 

Speaker: Maurice Herlihy, An Wang Professor of Computer Science, Brown University

Title: Correctness Conditions for Cross-chain Transactions

Abstract: Modern distributed data management systems face a new challenge: how can autonomous, mutually-distrusting parties cooperate safely and effectively? Addressing this challenge brings up many questions familiar from classical distributed systems. Nevertheless, many of these questions requires subtle rethinking when participants are autonomous and potentially adversarial. We propose the notion of a *cross-chain deal*, a new way to structure complex distributed computations that manage assets in an adversarial setting. Deals are inspired by classical atomic transactions, but differ in important ways to accommodate the decentralized and untrusting nature of the exchange. Joint work with Barbara Liskov and Liuba Shrira. This talk is intended for a general audience.

Bio: Maurice Herlihy has an A.B. in Mathematics from Harvard University, and a Ph.D. in Computer Science from M.I.T. He has served on the faculty of Carnegie Mellon University and the staff of DEC Cambridge Research Lab. He is the recipient of the 2003 Dijkstra Prize in Distributed Computing, the 2004 Gödel Prize in theoretical computer science, the 2008 ISCA influential paper award, the 2012 Edsger W. Dijkstra Prize, and the 2013 Wallace McDowell award. He received a 2012 Fulbright Distinguished Chair in the Natural Sciences and Engineering Lecturing Fellowship, and he is fellow of the ACM, a fellow of the National Academy of Inventors, the National Academy of Engineering, and the National Academy of Arts and Sciences. In 2022, he won his third Dijkstra Prize.

Members of the public (without Princeton affiliation) who wish to attend must register. PUID holders do not need to register.

Stay tuned for future DeCenter seminars! Monthly seminars will take place fully in-person on the first Thursday of the month from 12:30 p.m. – 1:20 p.m. in Computer Science Room 105. Videos of seminars will be made available after the event.

Space, Air, Ground Integrated Networking from Single – To Multi-Component Pareto Optimization

Date and Time
Thursday, October 13, 2022 - 12:30pm to 1:30pm
Location
Zoom Webinar (off campus)
Type
Seminar
Speaker
Lajos Hanzo, from University of Southampton, UK
Host
Kyle Jamieson & Yasaman Ghasempour

Lajos Hanzo
Princeton Wireless Distinguished Seminar Series

Thanks to the spectacular advances in signal processing and nano-technology, five wireless generations have been conceived over the past five decades. Indeed, near-capacity operation at an infinitesimally low error rate has become feasible and flawless multimedia communications is supported in areas of high traffic density, but how do we fill the huge coverage holes existing across the globe? As a promising system architecture, an integrated terrestrial, UAV-aided, airplane-assisted as well as satellite-based global coverage solution will be highlighted to pave the way for seamless next-generation service provision. However, these links exhibit strongly heterogeneous properties, hence requiring different enabling techniques. The joint optimization of the associated conflicting performance metrics of throughput, transmit power, latency, error probability, hand-over probability and link lifetime poses an extremely challenging problem. Explicitly, sophisticated multi-component system optimization is required for finding the Pareto-front of all optimal solutions, where none of the above-mentioned metric can be improved without degrading at least one of the others.

Bio: Lajos Hanzo is a Fellow of the Royal Academy of Engineering (FREng), FIEEE, FIET and a EURASIP Fellow, Foreign Member of the Hungarian Academy of Science. He holds honorary Doctorates from the University of Edinburgh and the Technical University of Budapest. He co-authored 19 IEEE Press – John Wiley books and 2000+ research contributions at IEEE Xplore. For further information on his research in progress and associated publications, please refer to IEEE Xplore.                


This talk will take place over Zoom (Please Register)

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