Easily understood visualization of the quantum software stack with the firmware layer in more detail. Worth the read at the link, below. Because Quantum is Coming. Qubit.
Quantum firmware and the quantum computing stack
+ The stack, shown above, in a fault-tolerant quantum computer is made of layers that correspond to levels of software abstraction. At the top sits Quantum As A Service (QAAS), which represents functions a user might interact with through, for instance, a cloud service. Below that are quantum algorithms and applications that are coded using developer tools that permit high-level abstraction. The algorithms and applications are compiled on the third level to enact circuits on encoded blocks. In fault-tolerant computing, that enaction is performed on logical qubits encoded using quantum error correction (QEC), although realizing the QEC code and other associated tasks occupies a dedicated layer. Physical connectivity between devices and compensation for any stray couplings are accounted for in a hardware-aware compiler. The quantum firmware layer, which is responsible for minimizing hardware error, resides between that layer and the physical hardware. It handles all tasks necessary for hardware calibration, tune-up, characterization, stabilization, and automation. (Image courtesy of Q-CTRL.)
+ Quantum firmware, depicted above, is an abstract layer of the computing stack whose actions are orchestrated by an embedded microprocessor. The microprocessor accesses cloud-computing resources for computationally intense tasks such as open-loop-control optimization and virtualizes the hardware for its interaction with higher layers of the software stack. In the conception shown here, the microprocessor sends commands to programmable logic devices, such as field-programmable gate arrays. Those devices are responsible for processing measurement results in real time for physical-layer feedback stabilization, measurement-based decision making, and other tasks. They also provide instructions to other hardware elements such as direct digital synthesizers and arbitrary waveform generators. Arrows indicate communication pathways between elements. (Image courtesy of Q-CTRL.)
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