Modern electronic and photonic technologies are increasingly being designed in the quantum regime, where classical descriptions collapse. To operate these quantum-scale technologies, researchers are investigating ways to replicate or surpass the feedback control tools that have traditionally been wildly successful in automating technologies from self-driving cars to adaptive cardiac pacemakers. In classical feedback control algorithms, decisions about how to control a system are based on measurements of the system’s behavior. However, in the quantum world, these measurements can add noise to the system, rendering the control loop imprecise. Now, researchers from the University of Basel, Switzerland, report on an implementation of “coherent” feedback control that promises to remove the need for measurements [1]. The method could thus potentially be applied to quantum technologies without deleterious effects.
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