Researchers from IDLab, an imec research group at Ghent University in Belgium, have created an ultra-low-noise balanced photonic-electronic detector for high-performance quantum communications and quantum computers. Their research published in Optica, an open-access journal by The Optical Society, is potentially transformative, as the first demonstrator at room temperature reaching sub-shot-noise region beyond 20 GHz.
Optical homodyne detection is a common building block used in numerous quantum and classic applications that demand high levels of sensitivity. So far, there are several practical limits on the performance of these devices. Mainly, the conventional use of bulk optics and discrete receiver electronics imposes a performance bottleneck. One can employ commercial integrated telecom amplifiers to improve performance. However, these amplifiers are not designed to operate at noise levels well below the shot-noise limit, because having ultralow noise performance does not yield significant improvements toward the bit error rates in digital communications systems. To address these performance issues, in the EU Quantum Flagship UNIQORN project, researchers from IDLab present a co-integrated balanced homodyne detector consisting of a silicon photonics optical front end and a custom integrated transimpedance amplifier designed in a 100 nm GaAs pHEMT technology.
(a) Micrograph of the ultra-low-noise balanced photonic-electronic detector, (b) measured common-mode rejection ratio, (c) noise performance in terms of quantum shot noise clearance.
“This was a significant accomplishment of the group. Thanks to the high level of co-design and co-integration, we were able to demonstrate, for the first time, a shot-noise-limited bandwidth of more than 20 GHz for such devices,” says Prof. Xin (Scott) Yin, Quantum Research Lead at the IDLab group. “The high performance of the device provides enhanced operation to many sensitive quantum applications such as continuous-variable quantum key distribution (CV-QKD), quantum random number generation (QRNG), or high-speed quantum tomography.”
The presented detector shows a linear operation up to 28 dB quantum shot noise clearance and a high degree of common-mode rejection. The clearance was measured up to 20 GHz and remained shot noise limited. At 20 GHz, the shot noise is still twice as large as the electronic noise with a clearance of 4.8 dB.
Cited article: Cédric Bruynsteen, Michael Vanhoecke, Johan Bauwelinck, and Xin Yin, “Integrated balanced homodyne photonic–electronic detector for beyond 20 GHz shot-noise-limited measurements,” Optica 8, 1146-1152 (2021)
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