[CS] Chris Kang Candidacy Exam/Oct 29, 2025

[via cs]

This is an announcement of Chris Kang's Candidacy Exam.
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Candidate: Chris Kang

Date: Wednesday, October 29, 2025

Time: 11 am CST

Remote Location: https://uchicago.zoom.us/j/97690380093?pwd=BaLLGHQ682n9lmBfguCM2CtOmAWGND.1&jst=3

Location: JCL 223

Title: Algorithms and Architectures for Practical Quantum Simulators

Abstract: In the 1980s, Feynman, Manin, and others envisioned a computer harnessing quantum phenomena to perform computations --- a quantum computer. Originally proposed to simulate physics, quantum computers can evade the curse of dimensionality that plagues classical simulations of quantum systems. Quantum simulations could efficiently elucidate fundamental natural processes that otherwise would be prohibitively costly to probe experimentally or intractable to simulate classically. Now, over four decades later, we are closer than ever to realizing quantum computers: experimentalists have advanced a variety of modalities for quantum computation, while theorists have steadily improved algorithms in asymptotic and constant terms.
But, despite substantial progress at the top and bottom of the quantum computing stack, the computational model and architecture of practical quantum simulators remains nascent and ambiguous. 

In this thesis, we pursue improvements in both algorithms and architectures: first, we propose a qubit-efficient algorithm for quantum linear algebra enabling efficient simulation of the Double Factorized Tensor HyperContracted (DFTHC) electronic Hamiltonian. This algorithm has significantly simpler circuits than the typical arithmetic subroutines required by qubitization, paving the way for RISC-like instances for quantum simulation. Second, we propose efficient compilations of Trotterized simulations compatible with error correction primitives, like lattice surgery. These compilations better approximate the actual cost of Trotterization by incorporating overheads from data routing and magic state cultivation. Finally, we introduce a new in situ scheme for learning pulses controlling analog quantum simulators. Analogous to post-silicon validation, this scheme could enable improved accuracy guarantees when simulating systems on analog quantum computers. 


Advisor: Fred Chong

Committee: Fred Chong, Bill Fefferman, Nathan Wiebe