A few projects that I have been a part of:
I have worked on Qiskit since 2018, although my activity has reduced as of late given that I am no longer primarily tasked with development. Currently Qiskit is the most widely used quantum computing software framework out there.
M3 (Matrix-free Measurement Mitigation) is a package designed for scalable mitigation of measurement errors in Qiskit. It works via a dimensional reduction step, followed by either direct LU factorization, or even better, via preconditioned matrix-free iterative methods. It is fast, efficient, and easy to use. It is also fun to work on.
Kaleidoscope is a visualization package for quantum computation that focuses on interactivity. In addition, there is a range of functionality for the Qiskit quantum computing framework for visualizing quantum systems and their associated properties. This is very much a side project until I get asked to make pretty plots for work, at which point it becomes super useful for visualizating IBM Quantum systems and their associated properties.
QuTiP is the original open-source library for quantum computation. QuTiP aims to provide user-friendly and efficient numerical simulations of a wide variety of Hamiltonians, including those with arbitrary time-dependence, commonly found in a wide range of physics applications such as quantum optics, trapped ions, superconducting circuits, and quantum nanomechanical resonators. It has been cited a couple thousand of times, and used across academia, research, and industrial institutions alike.
I have contributed a small amount to SciPy by adding a couple of sparse matrix
routines to the