When most people sit down at their computers to work, they’re thinking about all the things they need to get done; far from mind is any consideration of how their keystrokes and mouse clicks are translated into logic operations and electrical signals. That separation between hardware and user interface is the product of decades of development. Now quantum computer developers are navigating similar terrain.
The quantum computing stack is everything that lies between a user and the physical qubits. The stack needs to perform essential functions; for instance, it must facilitate user interaction, turn inputs into hardware manipulation, and correct for numerous error sources. (For more about quantum architectures, see the article by Anne Matsuura, Sonika Johri, and Justin Hogaboam, Physics Today, March 2019, page 40.) There’s no one right way to divide those tasks into discrete levels, though, and researchers and technology companies are still pursuing different visions for future quantum architectures.
On page 28 of Physics Today’s March 2021 issue, Harrison Ball, Michael Biercuk, and Michael Hush present the quantum computing stack proposed by Q-CTRL, the quantum technology company founded by Biercuk. The authors explain in detail how the functionality of a quantum firmware layer—one component of a quantum computer—is critical for managing qubit errors. Here we explain what happens in the rest of the layers of a quantum computer.
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