CS Special Talk with Tanuj Khattar and Adam Zalcman from Google Quantum AI

May 27, 2026

Speakers: Tanuj Khattar, Senior Research Scientist at Google Quantum AI, & Adam Zalcman, Engineering Manager at Google Quantum AI

Date: Wednesday, May 27, 2026

Time: 2:30–3:30 p.m.

Location: Henley Hall Lecture Room 1010

Host: Prabhanjan Ananth

Title: Securing Elliptic Curve Cryptocurrencies against Quantum Vulnerabilities: Resource Estimates and Mitigations

Abstract: The security of the modern digital economy, including nearly $3 trillion in cryptocurrency market capitalization, relies heavily on Elliptic Curve Cryptography (ECC). In this talk, we will explore the imminent threat Cryptographically Relevant Quantum Computers (CRQCs) pose to these decentralized networks. First, we provide new resource estimates for breaking the 256-bit Elliptic Curve Discrete Log Problem (ECDLP) over the secp256k1 curve, the core of modern blockchain cryptography. We demonstrate that Shor’s algorithm for this problem can execute with either ≤ 1200 logical qubits and ≤ 90 million Toffoli gates or ≤ 1450 logical qubits and ≤ 70 million Toffoli gates. In the interest of responsible disclosure, we used a zero-knowledge proof to validate these results without disclosing attack vectors - marking the first use of a ZKP to disclose a novel security threat. On superconducting architectures with 1e-3 physical error rates and planar connectivity, those circuits can execute in under 10 minutes using fewer than half a million physical qubits. Second, we examine the following underexplored intersections between quantum architectures and blockchain vulnerabilities:

Attack Vectors: We categorize quantum threats into "at-rest," "on-setup," and "on-spend" attacks, the latter of which can compromise active transactions within Bitcoin's standard block time.
Scale of Exposure: We quantify the immense risk across major networks, identifying 6.9 million vulnerable BTC (approximately $500 billion) and massive exposures within Ethereum's externally owned accounts, smart contracts, and validator consensus mechanisms.
Abandoned Assets & Policy: We address the systemic risk of over $150 billion in "lost" or dormant cryptographic assets. We will discuss the policy and protocol interventions necessary to prevent these assets from falling to adversaries, including regulated "digital salvage," protocol-level burns, and cryptographic escrows.

Ultimately, this talk serves as a stark warning to the cryptographic community: as hardware and algorithmic advances continuously drive down the cost of quantum cryptanalysis, decentralized networks must urgently and aggressively accelerate their migration to Post-Quantum Cryptography (PQC) before CRQCs arrive.

Speaker Bio (Tanuj): Tanuj Khattar is a Senior Research Scientist on the Quantum Algorithms and Applications Team within Google's quantum computing effort, Quantum AI. He specializes in optimizing quantum algorithms and building software tools for compilation and resource estimation of quantum algorithms.

Speaker Bio (Adam Zalcman): Adam Zalcman is an engineering manager at Google Quantum AI where he has been a driving force since the early quantum supremacy experiments in 2018. Today, he leads research and development teams focused on quantum error correction and compiling. Beyond fault tolerance, he conducts research into quantum algorithms and their practical applications.