Date: Thursday, March 19, 2026
Time: 1:00 pm
Location: EXP 610

Speaker: Prof. Saeed Mehraban (Department of Computer Science, Tufts University).

Title: Defining Quantum Computational Complexity over Continuous Variables.

Abstract: While the standard theory of quantum computing is formulated using discrete variable degrees of freedom such as electron spins, or the polarization of light, many degrees of freedom, such as electromagnetic amplitudes, or position and momentum of a particle, are described using continuous variables in infinite-dimensional Hilbert spaces. In recent years, quantum computing involving physical systems with continuous degrees of freedom has attracted significant interest. However, a well-defined quantum complexity theory for these bosonic computations over infinite-dimensional Hilbert spaces is missing. In this presentation, I will explain challenges and opportunities in defining a theory of quantum complexity over continuous degrees of freedom. 
 
A central message of our work is that, in the theory of quantum computation, we typically abstract away the details of physical implementation in order to obtain a mathematically self-contained notion of computation. We argue that this abstraction breaks down for continuous-variable systems: in this setting, the physical details cannot be cleanly separated from the computational model. In particular, if computation is defined in the usual way in terms of space and time resources, then continuous-variable quantum models allow one to embed towers of exponential-time classical computations into polynomial-time quantum computation.

Biography: Professor Saeed Mehraban is an assistant professor of Computer Science at Tufts University.  Saeed was an IQIM  postdoctoral scholar at the California Institute of Technology from 2019-2022, as well as a research fellow at the Quantum Wave in Computing Program at the Simons Institute for the Theory of Computing in Spring 2020. His research interests include quantum computation and information and their connections with theoretical computer science and physics.  
 
Saeed obtained his Ph.D. degree in Electrical Engineering and Computer Science from MIT, advised by Aram Harrow and Scott Aaronson. He completed a B.Sc. degree in Electrical Engineering and a B.Sc. degree in physics from the Sharif University of Technology in Tehran. 
 
Google Scholar: https://scholar.google.com/citations?hl=en&user=tVif3VUAAAAJ