KAIST signal processing trick boosts quantum light detection efficiency

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Researchers at the Korea Advanced Institute of Science and Technology have developed a signal processing technique that makes homodyne detection of ultrafast quantum states of light more efficient, according to Quantum Zeitgeist. Homodyne detection is a standard way to measure properties of light at the quantum level. It is used in quantum communication, quantum sensing and photonic quantum computing. The work has been published in Nature Communications

The team looked closely at how quadrature values, the measured properties of the light field, are extracted from detector signals. By studying how shot noise and electronic noise are correlated over time, they treated the problem as a generalised Rayleigh quotient problem and worked out an optimal way to weight the signal over time. That optimal weighting improved the signal to noise ratio by 135 percent over constant weighting and by 44 percent over peak shaped weighting

In experiments they observed squeezing of minus 2.60 and minus 2.67 dB, anti-squeezing of 4.93 and 4.99 dB and an electronic noise margin of about 13 dB. Squeezed light is a special quantum state with reduced noise in one property, and it is a key resource for quantum sensing and photonic quantum computers. The researchers wrote: "The optimal weight enhances the squeezing and anti-squeezing levels observed experimentally." Those are solid numbers for a pure processing change

The trick works because electronic noise is steady over time, while pulsed optical signals appear as short peaks. Weighting the measurement to focus on the peaks lets more of the quantum signal through relative to the noise. It is a neat example of how better data processing can improve results without changing the hardware. Photonic companies like Xanadu and ORCA rely on measurements of this kind

Do improvements in measurement and signal processing get overlooked compared with new hardware? And which photonic quantum approach do you think has the best chance?

New Signal Processing Boosts Quantum Light Detection Efficiencyquantumzeitgeist.com