Chip-Level GHz Capable Balanced Quantum Homodyne Receivers

• Published in: Journal of lightwave technology 2022-12, Vol.40 (23), p.7518-7528
• Main Authors: Milovancev, Dinka, Honz, Florian, Vokic, Nemanja, Achleitner, Martin, Laudenbach, Fabian, Pacher, Christoph, Hubel, Hannes, Schrenk, Bernhard
• Format: Article
• Language: English
• Subjects: Bandwidth; Capacitance; Circuits; Continuity (mathematics); Frequency ranges; Low noise; Operational amplifiers; Optical fiber communication; Optical receivers; optical signal detection; photodetectors; Photodiodes; Photonics; Quadrature phase shift keying; quantum communication; Quantum cryptography; random number generation; Random numbers; Receivers; Sensitivity; Single-photon avalanche diodes
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2022.3211095

We present a design of balanced homodyne receivers suitable for ultra-low noise quantum applications such as continuous-variable quantum key distribution and quantum random number generation. For best noise and bandwidth performance a die-level low-parasitic photodiode together with a low-noise high-speed transimpedance amplifier are explored together with a planar lightwave circuit splitter chip serving as a photomixer. Bandwidths of 750 MHz and 2.6 GHz were accomplished while maintaining optimum noise performance, as evidenced by very high quantum-to-classical noise ratios of 26.8 and 18.6 dB, respectively. A common-mode rejection ratio of at least 40 dB was achieved for a frequency range of up to 1 GHz. Its application for continuous-variable quantum key distribution was evaluated by means of estimations under a strict untrusted receiver assumption, showing its potential for generating up to 43 Mbit/s secure-key rate over a reach of 10 km, whereas up to 100 Mbit/s could be supported at shorter reaches. Moreover, the high quantum-to-classical clearance values can enable high quality quantum random number generation at Gb/s rates. The multi-purpose operation of the designed balanced receivers for classical communications was examined showing reception sensitivities of −55.8 and −52.6 dBm at 500 Mbit/s and 1 Gbit/s quadrature phase shift keying transmission, respectively, using the 750 MHz receiver. The faster 2.6 GHz receiver enabled 10 Gbit/s duobinary transmission at −14.8 dBm sensitivity.