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arXiv:1806.09393 · IEEE photonics journal

1.2-GHz Balanced Homodyne Detector for Continuous-Variable Quantum Information Technology

Xiaoxiong Zhang, Yichen Zhang, Zhengyu Li, Song Yu, Hong Mei Guo

Published Aug 23, 2018• 99 citations
arXivHTMLPDF

Abstract

Balanced homodyne detector (BHD) that can measure the field quadratures of coherent states has been widely used in a range of quantum information technologies. Generally, the BHD tends to suffer from narrow bands and an expanding bandwidth behavior usually traps into a compromise with the gain, electronic noise, and quantum to classical noise ratio, etc. In this paper, we design and construct a wideband BHD based on radio frequency and integrated circuit technology. Our BHD shows bandwidth behavior up to 1.2 GHz and its quantum to classical noise ratio is around 18 dB. Simultaneously, the BHD has a linear performance with a gain of 4.86 k and its common mode rejection ratio has also been tested as 57.9 dB. With this BHD, the secret key rate of continuous-variable quantum key distribution system has a potential to achieve 66.55 Mb/s and 2.87 Mb/s, respectively, at the transmission distance of 10 and 45 km. Besides, with this BHD, the generation rate of quantum random number generator could reach up to 6.53 Gb/s.

DOI
10.1109/jphot.2018.2866514

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Balanced homodyne detector (BHD) that can measure the field quadratures of coherent states has been widely used in a range of quantum information technologies. Generally, the BHD tends to suffer from narrow bands and an expanding bandwidth behavior usually traps into a compromise with the gain, electronic noise, and quantum to classical noise ratio, etc. In this paper, we design and construct a wideband BHD based on radio frequency and integrated circuit technology. Our BHD shows bandwidth behavior up to 1.2 GHz and its quantum to classical noise ratio is around 18 dB. Simultaneously, the BHD has a linear performance with a gain of 4.86 k and its common mode rejection ratio has also been tested as 57.9 dB. With this BHD, the secret key rate of continuous-variable quantum key distribution system has a potential to achieve 66.55 Mb/s and 2.87 Mb/s, respectively, at the transmission distance of 10 and 45 km. Besides, with this BHD, the generation rate of quantum random number generator could reach up to 6.53 Gb/s.
We present a high-performance, fully discrete balanced homodyne detector (BHD) with a 2.5 GHz bandwidth, exceptional gain flatness, and superior common-mode rejection ratio. The design leverages a Rogers 4350B-based printed circuit board, a broadband multi-section RF choke bias network, and inter-stage π-section attenuators, complemented by precise photodiode matching and phase-magnitude compensation to ensure signal integrity and suppress common-mode noise. Experimental results show a -3 dB bandwidth of 2.5 GHz and 1 dB gain flatness up to 2.4 GHz-significantly exceeding our prior 1.55 GHz/1.4 GHz implementation and representing state-of-the-art performance among discrete BHDs. At 16 mW optical input, the detector delivers a 16.5 dB signal-to-noise ratio at 2 GHz while maintaining excellent linearity, and achieves a 66 dB common-mode rejection ratio at the same frequency. This cost-effective and flexible BHD is ideally suited for high-speed continuous-variable quantum key distribution and quantum random number generation.
In the continuous-variable quantum key distribution (CV-QKD) system with a local local oscillator (LLO), the center frequency of the sender and the receiver’s source are not exactly the same and a certain frequency drift exists over time, resulting in the frequency of the signal received near the intermediate frequency. Therefore, the LLO system needs an intermediate-frequency balanced homodyne detector (BHD), which needs better symmetry of the arms of the BHD, to obtain the less-common mode noise. Moreover, the traditional intermediate-frequency receiver in classical communication is not available in the CV-QKD system because of the low quantum-to-classical noise ratio. In view of this, in this paper, we construct a broadband intermediate-frequency BHD based on ratio frequency and integrated circuit technology, whose bandwidth can exceed 270 MHz and whose quantum-to-classical noise ratio can reach 14.9 dB. Meanwhile, the BHD has an excellent linear performance with a gain of 22.4 k. By adopting our intermediate-frequency BHD, the secret key rate of the pilot-sequential Gaussian modulated coherent state CV-QKD system with an LLO can reach over 430.8 kbps of 60 km at the standard fiber length, which paves the way to achieve a high-performance LLO CV-QKD system with intermediate-frequency BHD.
In this paper, a model for simulating the shot noise power and the electronic noise power of a balanced homodyne detector (BHD) using cascaded low noise amplifiers (LNAs) is presented. Moreover, the factors influencing the enhancement of BHD gain flatness are analyzed. Based on these theories, a BHD with a large clearance between shot noise and electronic noise, along with a flat broadband frequency response, is designed using LNAs and an optimized printed circuit board design. According to the experimental measurements, the bandwidth for 1 dB flatness reaches 1.4 GHz with the -3 dB bandwidth extending up to 1.55 GHz. With a 4 mW optical signal input, a signal-to-noise ratio of 12 dB is obtained at 1 GHz. The BHD exhibits excellent linearity for shot noise output up to an 8 mW optical signal input and a tested common mode rejection ratio of 63 dB. This developed BHD is well-suited for applications in high-speed continuous variable quantum key distribution and quantum random number generation.
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.
We study a relatively excellent BHD(Balanced Homodyne Detector)with large bandwidth and low noise pre-amplification, which is different from the specific BHD implementation scheme and can better adapt to the subsequent cascade scheme, thereby achieving the implementation of BHD with specific needs. Specifically, we optimize our BHD performance by compromising various parameters of BHD, focusing on optimizing and increasing BHD bandwidth, and choosing a more reasonable BHD implementation solution. Judging from the test results, the produced BHD has good performance in extracting effective signals. The bandwidth reaches about 2GHz, which meets the requirements of detection applications. It has a high signal-to-noise ratio of 10 dB and a common-mode rejection ratio (CMRR) of 20 dB near the 2 GHz frequency point.