Quantum mechanics

Computer hardware

Quantum computer

Engineering

Feedback loop

Coherence (philosophical gambling strategy)

Control engineering

Computer security

Telecommunications

Computer science

Imaging phantom

Physics

Latency (audio)

Optics

Feed forward

Electronic engineering

Quantum

Gate array

Qubit

Field-programmable gate array

Physical Review Applied

Feedback is a main component of many algorithms for quantum computing and communication. A key requirement for any quantum feedback scheme is that the $l\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}y$ of the feedback loop ($i.e.$ the time between beginning to measure a state and the end of feedback action on the state) must be significantly shorter than the coherence time of the system. In this work a superconducting qubit is initialized in its ground state by active feedback, using a field-programmable gate array (FPGA) with very short latency. This in-depth discussion of the FPGA-based processing unit provides a useful reference for future development of feedback electronics for quantum systems.

Low-Latency Digital Signal Processing for Feedback and Feedforward in Quantum Computing and Communication