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Instrumentation and measurement

Instrumentation and measurement

New single-photon detector targets high-speed quantum communications

22 Feb 2023
Nanowire fan
Quantum fan: the new single-photon detector comprises 32 superconducting nanowires. (Courtesy: Ryan Lannom, JPL-Caltech/NASA)

A new photon detector called PEACOQ can register the arrival times of individual photons with the best timing resolution to date. Developed by Matthew Shaw and colleagues at NASA’s Jet Propulsion Laboratory, the detector achieved a maximum count rate of some 1.5 billion photons per second, while maintaining high efficiency and low noise.

Many schemes for quantum communications rely on the ability to detect and process light at the single-photon level, while logging the arrival times of each photon with pinpoint precision. As researchers seek to transmit quantum information at ever higher rates, the ability of detectors to register incoming photons will need to keep pace, without sacrificing low noise and high efficiency.

Superconducting nanowires are one of the most promising platforms for achieving ultra-high photon count rates. Cooled close to absolute zero, a nanowire will absorb a photon and heat up slightly. This reduces the nanowire’s the electrical resistance, which can be detected by measuring a drop in the current passing through the device. By recording the timing of this disruption, detectors can log photon arrival times with extreme accuracy.

Dead time limit

Nanowires have numerous advantages over other detection approaches. They detect photons across wavelengths across the mid-infrared to ultraviolet. Detection is done at efficiencies exceeding 98%, and at photon count rates up to 800 million photons per second. However, nanowires have one drawback that stops them from achieving even higher counting rates. The obstacle is the time taken for heat to dissipate from a nanowire after it has detected a photon. While a nanowire cools, a detector experiences a dead time where no new photons can be registered – limiting the count rate.

Now Shaw’s team has developed an advanced detector that offers a significant reduction in dead time. Dubbed the Performance-Enhanced Array for Counting Optical Quanta – or PEACOQ – the detector features an array of 32 straight, superconducting nanowires, which fan out like a peacock’s tail.

If any of PEACOQ’s nanowires absorb a photon, the resulting electrical signal is read out independently, then fed into a time-to-digital converter. This device records photon arrival times for all 32 nanowires simultaneously, to within a timing resolution of less than 100 ps. In the team’s experiments, PEACOQ achieved a maximum count rate of 1.5 billion photons per second – nearly double the rate of conventional nanowire detectors.

While the independent readout of each nanowire makes the device more complicated, the team was able to achieve low-noise operation and a detection efficiency of up to 78% – even when the detector was pushed to its limits. Shaw’s team is now trying to boost the efficiency. The researchers hope their design could pave the way for new advances in quantum key distribution cryptography.

The detector is described in Optica.

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