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Applied Computing for Scientific Discovery

Ed Younis

Ed Younis
Ed Younis
Computer Systems Engineer 3
Computer Science Department
LBNL Office: 50F-1620N
Eastern Time
Atlanta, Georgia

Ed works as a developer and researcher in the area of quantum software systems. Primarily, his work is focused on quantum synthesis. He actively contributes towards several projects in this category:

BQSKit: Berkeley Quantum Synthesis Toolkit. A quantum software system centered around synthesis.

QFAST: Quantum Fast Approximate Synthesis Tool. An optimizer-based synthesis tool that hierarchically breaks down large problems into smaller ones. This is done by employing a continuous Pauli encoding of quantum circuits.

qFactor: Quantum Fast Circuit Optimizer. A domain-specific optimizer for quantum circuits. qFactor uses analytic methods to minimize the distance between a circuit structure and a target unitary matrix.

Conference Papers

Mathias Weiden, Justin Kalloor, John Kubiatowicz, Ed Younis, Costin Iancu, "Wide Quantum Circuit Optimization with Topology Aware Synthesis", Third International Workshop on Quantum Computing Software, November 13, 2022,

Unitary synthesis is an optimization technique that can achieve optimal gate counts while mapping quantum circuits to restrictive qubit topologies. Synthesis algorithms are limited in scalability by their exponentially growing run times. Application to wide circuits requires partitioning into smaller components. In this work, we explore methods to reduce depth and multi-qubit gate count of wide, mapped quantum circuits using synthesis. We present TopAS, a topology aware synthesis tool that preconditions quantum circuits before mapping. Partitioned subcircuits are optimized and fitted to sparse subtopologies to balance the opposing demands of synthesis and mapping algorithms. Compared to state of the art wide circuit synthesis algorithms, TopAS is able to reduce depth on average by 35.2% and CNOT count by 11.5% for mesh topologies. Compared to the optimization and mapping algorithms of Qiskit and Tket, TopAS is able to reduce CNOT counts by 30.3% and depth by 38.2% on average.

Ethan H. Smith, Marc G. Davis, Jeffery M. Larson, Costin Iancu, "LEAP: Scaling Numerical Optimization Based Synthesis Using an Incremental Approach", International Workshop of Quantum Computing Software at Supercomputing, November 2020,


Ed Younis, Koushik Sen, Katherine Yelick, Costin Iancu, QFAST: Quantum Synthesis Using a Hierarchical Continuous Circuit Space, Bulletin of the American Physical Society, March 2021,

We present QFAST, a quantum synthesis tool designed to produce short circuits and to scale well in practice. Our contributions are: 1) a novel representation of circuits able to encode placement and topology; 2) a hierarchical approach with an iterative refinement formulation that combines "coarse-grained" fast optimization during circuit structure search with a good, but slower, optimization stage only in the final circuit instantiation. When compared against state-of-the-art techniques, although not always optimal, QFAST can reduce circuits for "time-dependent evolution" algorithms, as used by domain scientists, by 60x in depth. On typical circuits, it provides 4x better depth reduction than the widely used Qiskit and UniversalQ compilers. We also show the composability and tunability of our formulation in terms of circuit depth and running time. For example, we show how to generate shorter circuits by plugging in the best available third party synthesis algorithm at a given hierarchy level. Composability enables portability across chip architectures, which is missing from similar approaches.
QFAST is integrated with Qiskit and available at