High-Speed Quantum Radio-Frequency-Over-Light Communication

Shaocong Liang, Jialin Cheng, Jiliang Qin, Jiatong Li, Yi Shi, Zhihui Yan, Xiaojun Jia, Changde Xie, and Kunchi Peng

Phys. Rev. Lett. 132, 140802 – Published 3 April 2024

Abstract

Quantum dense coding (QDC) means to transmit two classical bits by only transferring one quantum bit, which has enabled high-capacity information transmission and strengthened system security. Continuous-variable QDC offers a promising solution to increase communication rates while achieving seamless integration with classical communication systems. Here, we propose and experimentally demonstrate a high-speed quantum radio-frequency-over-light (RFOL) communication scheme based on QDC with an entangled state, and achieve a practical rate of 20 Mbps through digital modulation and RFOL communication. This scheme bridges the gap between quantum technology and real-world communication systems, which bring QDC closer to practical applications and offer prospects for further enhancement of metropolitan communication networks.

Received 18 December 2023
Accepted 12 March 2024

DOI:https://doi.org/10.1103/PhysRevLett.132.140802

Physics Subject Headings (PhySH)

Optical quantum information processing Quantum communication Quantum communication, protocols & technology Quantum networks Quantum optics

Quantum Information, Science & TechnologyAtomic, Molecular & Optical

Authors & Affiliations

Shaocong Liang ^1,*, Jialin Cheng ^1,*, Jiliang Qin^1,2, Jiatong Li¹, Yi Shi¹, Zhihui Yan ^1,2,†, Xiaojun Jia ^1,2,‡, Changde Xie^1,2, and Kunchi Peng^1,2

¹State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People’s Republic of China
²Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People’s Republic of China

^*These authors contributed equally to this work.
^†zhyan@sxu.edu.cn
^‡jiaxj@sxu.edu.cn

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Issue

Vol. 132, Iss. 14 — 5 April 2024

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Images

Figure 1
Schematic diagram. (a) Schematic diagram of QDC with a broadband entangled state. The configuration involves sharing a broadband entangled state of light between Alice and Bob. Alice encodes two wideband signals onto the quadrature amplitude and phase, respectively, of the entangled submode, which is then transmitted to Bob. Bob receives the submode and decodes information with the assistance of the other submode. Amplitude modulator (AM); phase modulator (PM); balanced homodyne detector (BHD); demodulation and measurement (D&M). (b) Comparison of the power spectra of traditional CV-QDC and our scheme. The leftmost $δ$ -shaped peak represents the traditional QDC spectrum with information typically encoded at the frequency point $f_{0}$ . The right side illustrates a carrier signal capable of accommodating high-speed digital information, characterized by a specific frequency bandwidth.
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Figure 2
Experimental results. (a) Comparison between the baseband signal and the demodulated signal on the oscilloscope. The orange and blue curves are the original signal and the demodulated signal with quadrature phase correlation, respectively. (b) An enlarged view of the period marked by the dotted line in (a) (from 10.1 to $11.5 μ s$ ) along with the symbol decision results. (c) BER comparison. The green, blue, and magenta curves represent the relationships between the BER of the demodulated information and the SNR achieved with the BASK, BFSK, and BPSK modulation methods, respectively. The red and black dots indicate the actual BERs obtained in the experiment. These values are determined via quadratures encoding and decoding using the BPSK modulation technique. The points within the square, triangular, and circular regions represent the results measured with the single submode (thermal state), the coherent state, and the combined submodes (entangled state), respectively, where the same modulation signal is used in all three cases. The error bars are derived from 5 consecutive BER measurements each based on $10^{5} bits$ .
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Figure 3
Comparison between the original and received images when using different communication methods. (a) The original dichroic $250 \times 400 pixel$ image to be transmitted. (b)–(d) [(e)–(g)] Images obtained by performing encoding and decoding on the quadrature phase $\hat{Y}$ (amplitude $\hat{X}$ ) of the optical carrier, where (b) [(e)], (c) [(f)], and (d) [(g)] are the images received with entangled state, coherent state, and the single submode, respectively.
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