Quantum microwave photonics

By harnessing quantum superposition and entanglement, remarkable progress has sprouted over the past three decades from different areas of research in communication, computation and simulation.

Microwave photonics (MWP) typically using classic optical methods and devices to generate, transport, and process radio-frequency (RF) signals  is a recently developed area of research which has greatly improved the microwave processing system in frequency, bandwidth, dynamic range and anti-interference. However, increasing bandwidth demands a higher electrical transmission bandwidth and a larger optical power at the photodetector because of the gain-bandwidth product of the detector.

Considering that the photonic quantum technologies are adept at manipulating and processing the photon signal with extremely low optical power, further acquiring improvement for the MWP processing is expected by introducing the photonic quantum devices.

Chinese Researchers led by Yaqing Jin, from National Time Service Center Chinese Academy Of Sciences have demonstrated a quantum microwave photonic processing system by combining the MWP link with the single-photon technology, reported in Jan 2021.

To further improve the processing ability of microwave pho-tonics, here, we have demonstrated a quantum microwave photonic processing system using a low jitter superconducting nanowire single photon detector (SNSPD) and a time-correlated single-photon counting (TCSPC) module.

This method uniquely combines extreme optical sensitivity, down to a single-photon level (below -100 dBm), and wide processing bandwidth, twice higher than the transmission bandwidth of the cable. Moreover, benefitted from the trigger, the system can selectively process the desired RF signal and attenuates the other in-tense noise and undesired RF components even the power is 15dB greater than the desired signal power.

With the help of the low jitter SNSPD and TCSPC, the processing system has both extreme sensitivities, down to a single-photon detection event, and wide processing bandwidth. Through the conversion between the high-speed optical waveform and the single-photon flux signal, our system, overcoming the electronic bandwidth after the SNSPD, can process the wide-bandwidth RF signal, whose frequency is significantly higher than the transmission bandwidth. Moreover, relying on the trigger clock, the system effectively attenuates the intense noise and selectively processes the desired RF input. Besides the potential application in high loss system, our system can be highly potential to process high-speed RF signals with the quantum processing method. For example, such quantum microwave photonic can further combine with the entangle feature to illustrate the nonlocal or secure quantum microwave processing

Using this method we show microwave phase shifting and frequency filtering for the desired RF signal on the single-photon level. Besides its applications in space and under-water communications and testing and qualification of pre-packaged photonic modulators and detectors. This RF signal processing capability at the single-photon level can lead to significant development in the high-speed quantum processing method.