KAIST researchers have developed signal processing that makes ultrafast quantum light easier to detect. Their peer-reviewed work changes how electrical detector signals contribute to a measurement, using their timing to separate the light signal from noise. The advance concerns the reading of an existing quantum state, with the detector’s response at the center of the work.
Researchers at the Korea Advanced Institute of Science and Technology, known as KAIST, have developed signal processing to improve the detection of ultrafast quantum light. The advance changes how electrical signals from a detector are combined into a measurement. Quantum states carried by very short light pulses can be difficult to read when the useful signal sits alongside electronic noise.[1], [2]
In homodyne detection, light interacts with a reference field so that a component of its quantum state can be measured. The detector's response to a short pulse spreads over time. Taking a sample at only one instant can therefore leave useful information out of the measurement. The peer-reviewed Communications Physics work instead combines signals from different moments using selected time weights.[1]
The team analyzed optical shot noise and electronic noise separately, then calculated weights for the detector samples. Signals synchronized with the light pulses differed from electronic noise in their timing. The selected weighting made squeezing and anti-squeezing, two quantum-optical measurement levels, more clearly visible. The improvement comes from processing the detector response; the light source itself was not made stronger.[1]
