Colloquium – Zane Rossi

Zane Rossi, University of Tokyo

The art of (quantum) computer programming

As quantum computing hardware rapidly improves, we need more quantum algorithms. Quantum algorithms appear to offer huge speedups for specific tasks, but examples are narrow, disparate, and often abstrusely presented. Our intuition for when (and why) a quantum algorithm outperforms its classical counterpart is still developing—there are no ‘natural’ quantum programmers yet.

How do we build mathematical training wheels for the quantum algorithmist that can take over when classical intuition falters?

A partial remedy has emerged with the development of a new family of quantum algorithms, including quantum signal processing (QSP) and quantum singular value transformation (QSVT), which have shown success in unifying and improving most known quantum algorithms. These algorithms can transform the spectra of linear operators encoded in unitary processes by near arbitrary functions, and this basic ability—computing matrix functions quantum-mechanically—can subsume diverse tasks with comparatively simple analysis.

In this colloquium I will situate these developments within modern quantum algorithms research, as well as motivate and present recent work showing that QSP and QSVT should not be viewed solely as subroutines for transforming linear operators, but instead as specific examples among a much wider class of techniques for converting quantum algorithmic problems to simpler algebraic and functional analytic ones. One benefit of these techniques is that they can serve as ‘handholds and guardrails’ by which one can reduce reasoning about the correctness, efficiency, and composition of quantum algorithms to simpler mathematical statements (for which we often have both accrued intuition and numerical tools). In turn, these guardrails support a virtuous cycle (familiar to classical computer science) wherein one can (1) investigate algorithms heuristically/numerically, (2) generate robust abstractions, and (3) flexibly compile the resulting algorithms to realistically constrained hardware.

Bio: Dr. Zane Rossi completed his doctorate at MIT and currently studies the theory of quantum algorithms at the University of Tokyo. His work draws on techniques from algebraic geometry, functional analysis, and category theory to construct interpretable quantum algorithms for common problems in numerical linear algebra.

January 28, 2026 @ 1:00pm (CST) in Commons Center 237

Host: Kalman Varga