China announced it has begun mass producing the world's first ultra-low noise, single-photon detector featuring four channels, suggesting that powerful applications loom in everything from daily communications to national defence.
Dubbed the "photon catcher", the device can detect a single photon - the smallest unit of energy - making it a core component in cutting-edge technologies such as quantum communication and quantum radar for stealth aircraft detection and tracking.
The feat was achieved by the Quantum Information Engineering Technology Research Centre in Anhui province and reported last Friday by Science and Technology Daily, a publication of China's Ministry of Science and Technology.
According to the newspaper, China, through its mass production, has achieved self-sufficiency and international leadership in the core components for quantum information technology.
A single-photon detector, as the name suggests, is an ultra-sensitive device capable of detecting individual photons.
When the human eye views an image, countless photons enter the eye simultaneously. Isolating just one photon has been described as akin to distinguishing the sound of a single grain of sand falling amid a thunderstorm.
The ability to detect individual photons means that even the faintest energy signals can be picked up, something considered fundamental to realising quantum communications and quantum radar technologies.
At present, conventional stealth aircraft like the American-made F-22 rely on specialised coatings and airframe designs to absorb or deflect radio waves, making them invisible to traditional radar.
Quantum radar operates differently. When a stealth aircraft intercepts photons emitted by quantum radar, the original quantum properties of those photons are altered.
Even the false signals emitted by the aircraft cannot replicate the original photon's physical characteristics under the no-cloning theorem of quantum mechanics.
By analysing the state of the single photons reflected from the target, quantum radar can effectively see through such deception.
In addition, quantum radar improves the detection of low-visibility targets, yet it consumes relatively little power and can be deployed across various platforms.
And in emitting minimal energy, quantum radar itself is difficult to detect and offers greater reliability and secrecy in complex electromagnetic environments.
Friday's announcement came nearly a decade after China pioneered another advance in single-photon detection.
In 2016, China Electronics Technology Group Corporation successfully developed the country's first quantum radar system based on single-photon detection, achieving a detection range of more than 100km (62 miles).
In the latest advance, the detector's four-channel functionality allows for the simultaneous reception of photons from either four different light sources or different parts of the same source, enabling parallel measurements.
In radar applications, this capability makes simultaneous scanning easier and improves imaging rates. Theoretically, researchers could equip each channel with different filters to synchronously detect single-photon signals across various wavelengths.
Previously, only single-channel engineered products were available internationally, requiring multiple units to work together in complex detection scenarios, according to Science and Technology Daily.
The new four-channel detector is just one-ninth the size of comparable international single-channel products. Even so, it is much more efficient in detection and sets a new standard in picking up extremely weak light, according to the report.
In an interview with Science and Technology Daily, Fang Yuqiang of QuantumCTek Co, whose research and development team developed the detector, said "the main challenge was achieving low temperature, low noise and multiple channels on a cryocooler the size of a human fist".
After more than three years of effort, the R&D team overcame significant technical hurdles, including the miniaturisation of thermoacoustic cryocoolers, ensuring seal reliability and suppressing inter-channel crosstalk, Fang added.
The team reduced the minimum operating temperature of a single cryocooler from minus 50 degrees Celsius (minus 58 degrees Fahrenheit) to minus 120 degrees.
At 20 per cent detection efficiency, the detector's dark count rate was reduced by about 90 per cent. As a rule, the lower a detector's dark count rate, the more sensitive it is in picking up signals.
Tang Shibiao, director of the research centre in Anhui, said he believed the product set a new global standard in performance metrics.
Tang echoed the ministry in saying China had achieved self-sufficiency in core quantum information components and modules.
The detectors are already serving top Chinese research institutions, and the centre can now produce and deliver them.
"In the future, we will provide a 'Chinese solution' for major projects such as the next-generation quantum communication network," Tang added.
Beyond quantum technology, this ultra-sensitive detector has potential applications in bio-fluorescence imaging, deep-space laser ranging and single-photon imaging, according to Science and Technology Daily.