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Master equation to boost quantum technologies

Björn Annby-Andersson and Peter Samuelsson
The researchers Peter Samuelsson and Björn Annby-Andersson in front of a white board. Photo: Johan Lindskoug

NanoLund researchers Björn Annby-Andersson and Peter Samuelsson have developed a “master equation” that will help engineers understand feedback at the quantum scale.

Many everyday technologies make use of feedback control routinely in order to manage operations of devices and processes. But physicists do not yet have an equivalent understanding of feedback control at the quantum level. 

Annby-Andersson and his colleagues have now developed a master equation, called a “Quantum Fokker-Planck equation”, that enables physicists to track the evolution of any quantum system with feedback control over time.

“The equation can describe scenarios that go beyond linear feedback,” says Annby-Andersson.
“In particular, the equation can be solved with pen and paper, rather than having to rely on computer simulations.”

The work has been done in collaboration with researchers from the University of Maryland and the University of Basel. The research is funded by The Foundational Questions Institute, FQXi, which works to catalyze, support, and disseminate research on questions at the foundations of science, particularly new frontiers in physics and innovative ideas integral to a deep understanding of reality but unlikely to be supported by conventional funding sources. Visit for more information.

Read the full Lund University news article in Swedish

Read about the research in English.

The study was published in Physical Review Letters: ”Quantum Fokker-Planck Equation for Continuos Feedback Control”