Portrait of Mostafizur Rahaman

Dr. Mostafizur Rahaman

  • Researcher, KTH Royal Institute of Technology, Sweden
  • Research Scientist, IBM Quantum (currently on leave)
  • Visiting Scientist, RIKEN Center for Quantum Computing, Japan

Research

How do we represent, process, and infer information in a noisy world, and what changes when quantum physics does the representing?

We study information at the meeting point of quantum physics, signal processing, and computation. Signals from a molecule's energy spectrum, a wireless channel, or a heartbeat all carry hidden mathematical structure. Our work asks what happens when that structure is expressed in quantum form: what becomes easier to compute, what becomes harder to measure, and what new kinds of inference become possible.

At the core of our approach is structure-aware quantum algorithm design. By exploiting patterns such as sparsity, banded and Toeplitz operators, and polynomial representations, we build quantum algorithms for simulation, spectral estimation, and filtering whose cost and error we can state precisely. The goal is not just a working circuit, but a clear account of how accuracy, depth, and resources scale together.

We also study how open quantum systems learn and remember. Through quantum reservoir computing, weak measurement, and dissipative dynamics, we explore how physical quantum systems process information over time, with direct relevance to biosignals and sensor streams.

Throughout, we keep our ideas grounded in real hardware and real problems. Working with IBM Quantum and RIKEN, we test our methods on superconducting processors and apply them to molecular simulation, biomedical signal processing, communication, and sensing, asking what today's noisy devices can actually deliver.

Research topics

Quantum Signal & Information Processing

What does it mean to represent a signal quantum mechanically? We encode signals, distributions, and operators as quantum states and ask how filtering, spectral analysis, and estimation change as a result: what can be inferred, at what cost, and under what uncertainty limits. Applications include biomedical signal denoising and source detection in large sensor arrays.

Quantum Algorithms, Simulation & Complexity

Many operators in science and engineering have structure: Toeplitz, Hankel, banded, or sparse. We design Hamiltonian simulation and eigenspectrum estimation algorithms that exploit this structure to reduce gate count and circuit depth, with rigorous error analysis and resource estimates for running them on today's superconducting hardware.

Functional Approximation & Quantum Encoding

Before a continuous function or physical operator can be processed on a quantum computer, it must be approximated and encoded. We develop polynomial and basis expansions that make this step explicit and controllable, showing exactly how accuracy trades against circuit resources, as demonstrated in simulating molecular potential energy operators.

Quantum Learning & Open Dynamics

How do noisy, open quantum systems remember and process information over time? We study quantum reservoir computing, weak measurement, and Lindblad dynamics to understand memory and learning capacity in physical quantum systems, and apply shallow entangled circuits to time-series prediction on real quantum devices.

Trajectory

Aug. 2026 – Present

Researcher (Senior Postdoc), KTH Royal Institute of Technology

Quantum information processing, learning theory, and quantum algorithms at the School of Electrical Engineering and Computer Science.

Sept. 2025 – Present

Visiting Scientist, RIKEN Center for Quantum Computing

Quantum information physics, quantum reservoir computing, weak measurement, and open quantum dynamics.

Jan. 2024 – Jul. 2026 · currently on sabbatical

Research Scientist, IBM Quantum Division

Hardware-aware quantum algorithms, functional approximation, circuit compilation, quantum-centric computation, and experiments on superconducting quantum processors.

Sept. 2020 – Feb. 2025

Ph.D., IIT Kharagpur · Prime Minister's Research Fellow

Synopsis submitted in Oct. 2023; defended in Feb. 2025. Quantum algorithms and architectures for structured Hamiltonian operators with efficient gate complexity.

Jan. 2018 – Sept. 2020

M.S. (Research), IIT Kharagpur

Synopsis submitted in Feb. 2020; defended in Sept. 2020. Research in statistical signal processing, estimation, and learning.

Selected publications

  1. Scientific Reports

    Shallow Entangled Circuits for Quantum Time Series Prediction on IBM Devices

  2. Scientific Reports

    Efficient Simulation of Potential Energy Operators on Quantum Hardware: A Study on Sodium Iodide (NaI)

  3. Scientific Reports

    A Complexity Efficient Penta-Diagonal Quantum Smoothing Filter for Bio-Medical Signal Denoising

  4. IEEE Transactions on Quantum Engineering

    A Low-Complexity Quantum Simulation Framework for Toeplitz-Structured Matrix and Its Application in Signal Processing

  5. IEEE Transactions on Communications

    Eigen-Spectrum Estimation and Source Detection in a Massive Sensor Array Based on Quantum Assisted Hamiltonian Simulation Framework

Current collaborators

  • Prof. Mikael Skoglund
    KTH Royal Institute of TechnologyProfessor of Communication Theory; Head, Department of Information Science and Engineering.
  • Prof. Gabor Fodor
    KTH Royal Institute of Technology / Ericsson ResearchAdjunct Professor at KTH and researcher at Ericsson Research.
  • Prof. Franco Nori
    Quantum Information Physics Theory Research Team, RIKEN Center for Quantum ComputingTeam Director; concurrent affiliation with the University of Michigan, Ann Arbor.
  • Dr. Clemens Gneiting
    Quantum Information Physics Theory Research Team, RIKEN Center for Quantum ComputingResearch Scientist working on open quantum dynamics and quantum information.
  • Dr. Neill Lambert
    Quantum Information Physics Theory Research Team, RIKEN Center for Quantum ComputingSenior Research Scientist; open quantum systems and quantum environments.
  • Prof. Tanusri Saha-Dasgupta
    S. N. Bose National Centre for Basic SciencesDirector and Senior Professor; computational materials physics and quantum materials.
  • Prof. Manoranjan Kumar
    S. N. Bose National Centre for Basic SciencesProfessor; strongly correlated systems, quantum computing, and numerical methods.

Contact

KTH Royal Institute of Technologymorl@kth.se
IBM Quantumrahaman1@ibm.com