Print As one of the fundamental functions of microwave photonic signal processing, microwave photonic (MWP) mixers are indispensable to modern radar and wireless communication systems. However, the classical MWP mixers are dependent on the loading of the radio-frequency(RF) signal and the local oscillator onto the same optical light source. This requirement limits its application in distributed radar systems.
Recently, the research team led by Prof. DONG Ruifang from the National Time Service Center (NTSC) of the Chinese Academy of Sciences (CAS) has achieved nonlocal frequency mixing of two spatially separated RF signals using quantum entanglement. The team employed an energy-time entangled biphoton source as the optical carrier, leveraging the intrinsic time-correlation between photon pairs to overcome traditional spatial constraints.
The results have been published on PHYSICAL REVIEW APPLIED, 2025, 23, 014078.
Specifically, the researchers explored quantum microwave photonic mixers (QMWPs) in two configurations: cascaded type and parallel type. "The research shows that both QMWP mixers not only have the ability of nonlocal mixing, but also feature high linearity and the ability to output mixed signals through dual channels. Moreover, the key performance indicator of the quantum microwave photonic mixer, the spurious-free dynamic range, is consistent with that of the classical microwave photonic mixer." said Dr. LI Xinghua, the first author of this research.
The nonlocal QMWP mixing capability of the QMWP mixer can be further expanded to a multichannel mixer by using multiphoton frequency-entangled sources as the optical carrier. "This kind of extension is conducive to enhancing the performance of multichannel microwave photonic mixing and is of vital significance for optimizing the performance of radar network systems," said Prof. DONG.
This innovation marks a significant step forward in quantum microwave photonic signal processing, with potential applications in distributed radar and secure wireless communication systems.
QMWP mixers with the RF modulators in (a) cascade-type and (b) parallel-type configurations. (Image by NTSC)