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Quantum Optics and Quantum Information|34 Article(s)
Integration of classical communication and quantum key distribution using frequency division multiplexing
Yunyu Shao, Ziyi Shen, Yuehan Xu, Lang Li, Zicong Tan, Xiaojuan Liao, Peng Huang, Tao Wang, and Guihua Zeng
Since the working conditions of classical and quantum signals are very different, how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge. In this paper, we proposed a scheme to realize classical communication and continuous-variable quantum key distribution (CV-QKD) based on frequency-division multiplexing (FDM), and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure. We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86 × 105 bit/s for the quantum signal through a 4 dB fiber channel. This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength, increasing efficiency and simplifying the integration of QKD and classical communication. Since the working conditions of classical and quantum signals are very different, how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge. In this paper, we proposed a scheme to realize classical communication and continuous-variable quantum key distribution (CV-QKD) based on frequency-division multiplexing (FDM), and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure. We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86 × 105 bit/s for the quantum signal through a 4 dB fiber channel. This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength, increasing efficiency and simplifying the integration of QKD and classical communication.
Chinese Optics Letters
- Publication Date: Mar. 25, 2025
- Vol. 23, Issue 3, 032702 (2025)
Quantum erasure based on orbital angular momentum of photons
Ye Yang, Chengyuan Wang, Yun Chen, Jianyi Xu, Xin Yang, Jinwen Wang, Enqi Zhang, Shuwei Qiu, Hong Gao, and Fuli Li
The quantum eraser effect exemplifies the distinctive properties of quantum mechanics that challenge classical intuition and reveal the wave-particle duality of light. Whether the photon exhibits particle-like or wave-like behavior depends on whether the path information is discernible. In this paper, we propose a novel quantum eraser scheme that utilizes photonic phase structures as the which-way indicator. This scheme is implemented using a Mach–Zehnder interferometer (MZI), where one arm is configured with orbital angular momentum (OAM) to establish predetermined which-way information. Consequently, at the output ports of the MZI, the photon displays particle-like characteristics when the which-way information is retained. However, the introduction of an additional spiral phase plate (SPP) to eliminate the phase structure from the output photon of the MZI unveils distinct interference patterns. This result enhances our understanding of the quantum erasure effect. The quantum eraser effect exemplifies the distinctive properties of quantum mechanics that challenge classical intuition and reveal the wave-particle duality of light. Whether the photon exhibits particle-like or wave-like behavior depends on whether the path information is discernible. In this paper, we propose a novel quantum eraser scheme that utilizes photonic phase structures as the which-way indicator. This scheme is implemented using a Mach–Zehnder interferometer (MZI), where one arm is configured with orbital angular momentum (OAM) to establish predetermined which-way information. Consequently, at the output ports of the MZI, the photon displays particle-like characteristics when the which-way information is retained. However, the introduction of an additional spiral phase plate (SPP) to eliminate the phase structure from the output photon of the MZI unveils distinct interference patterns. This result enhances our understanding of the quantum erasure effect.
Chinese Optics Letters
- Publication Date: Mar. 19, 2025
- Vol. 23, Issue 3, 032701 (2025)
Squeezing-enhanced resolution of radio-frequency signals
Wei Li, Mingjian Ju, Qinghui Li, Ruixin Li, Wenxiu Yao, Yimiao Wu, Yajun Wang, Long Tian, Shaoping Shi, and Yaohui Zheng
We demonstrate a resolution enhancement scheme of radio-frequency signals by tailoring a phase-squeezed state. The echo radio-frequency signals collected by photonic radar give rise to displacements in the phase quadrature of a probe laser and are estimated by the balanced homodyne detector. In contrast to the conventional coherent state, the noise variances for radio-frequency estimation with a squeezed state are reduced by approximately 6.9 dB. According to the Rayleigh criterion that defines the resolution limit, the minimum resolvable displacement Δa with a squeezed state is reduced to 45% compared to that with a coherent state, demonstrating the quantum advantage. The squeezing-enhanced technique has extensive applications for multitarget recognition and tracking in contemporary photonic radar systems. We demonstrate a resolution enhancement scheme of radio-frequency signals by tailoring a phase-squeezed state. The echo radio-frequency signals collected by photonic radar give rise to displacements in the phase quadrature of a probe laser and are estimated by the balanced homodyne detector. In contrast to the conventional coherent state, the noise variances for radio-frequency estimation with a squeezed state are reduced by approximately 6.9 dB. According to the Rayleigh criterion that defines the resolution limit, the minimum resolvable displacement Δa with a squeezed state is reduced to 45% compared to that with a coherent state, demonstrating the quantum advantage. The squeezing-enhanced technique has extensive applications for multitarget recognition and tracking in contemporary photonic radar systems.
Chinese Optics Letters
- Publication Date: Jul. 30, 2024
- Vol. 22, Issue 7, 072701 (2024)
Polarization-entangled photon pairs with factorable spectra engineered by using an uneven four-stage nonlinear interferometer
Liang Cui, Haoran Chen, Jiamin Li, and Xiaoying Li
We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses. The uneven nonlinear interferometer, providing a more ideal interference pattern due to the elimination of secondary maxima, consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers, and the lengths of the nonlinear fibers follow the binomial distribution. The mode number of the photon pairs deduced from the measured joint spectrum is ∼1.03. The collection efficiency of the photon pairs is found to be ∼94% (after background noise correction). The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is ∼92%, while no interference is observed in the direct detection of either the signal or idler photons. We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump pulses. The uneven nonlinear interferometer, providing a more ideal interference pattern due to the elimination of secondary maxima, consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers, and the lengths of the nonlinear fibers follow the binomial distribution. The mode number of the photon pairs deduced from the measured joint spectrum is ∼1.03. The collection efficiency of the photon pairs is found to be ∼94% (after background noise correction). The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is ∼92%, while no interference is observed in the direct detection of either the signal or idler photons.
Chinese Optics Letters
- Publication Date: May. 14, 2024
- Vol. 22, Issue 5, 052701 (2024)
Acousto-optic modulator-based bi-frequency interferometer for quantum technology|Editors' Pick
Wenqi Li, Qiqi Deng, Xueshi Guo, and Xiaoying Li
We demonstrate a high-performance acousto-optic modulator-based bi-frequency interferometer, which can realize either beating or beating free interference for a single-photon level quantum state. Visibility and optical efficiency of the interferometer are (99.5±0.2)% and (95±1)%, respectively. The phase of the interferometer is actively stabilized by using a dithering phase-locking scheme, where the phase dithering is realized by directly driving the acousto-optic modulators with a specially designed electronic signal. We further demonstrate applications of the interferometer in quantum technology, including bi-frequency coherent combination, frequency tuning, and optical switching. These results show the interferometer is a versatile device for multiple quantum technologies. We demonstrate a high-performance acousto-optic modulator-based bi-frequency interferometer, which can realize either beating or beating free interference for a single-photon level quantum state. Visibility and optical efficiency of the interferometer are (99.5±0.2)% and (95±1)%, respectively. The phase of the interferometer is actively stabilized by using a dithering phase-locking scheme, where the phase dithering is realized by directly driving the acousto-optic modulators with a specially designed electronic signal. We further demonstrate applications of the interferometer in quantum technology, including bi-frequency coherent combination, frequency tuning, and optical switching. These results show the interferometer is a versatile device for multiple quantum technologies.
Chinese Optics Letters
- Publication Date: Feb. 22, 2024
- Vol. 22, Issue 2, 022703 (2024)
Generation of visible Raman operation laser by a fiber electro-optical modulator feedback loop
Rui-Rui Li, Wei-Ran Ye, Yi-Long Chen, Shu-Qian Chen, Wen-Hao Qi, Jin-Ming Cui, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
Phase-coherent multi-tone lasers play a critical role in atomic, molecular, and optical physics. Among them, the Raman opeartion laser for manipulating atomic hyperfine qubits requires gigahertz bandwidth and low phase noise to retain long-term coherence. Raman operation lasers generated by directly modulated and frequency-multipled infrared lasers are compact and stable but lack feedback control to actively suppress the phase noise, which limits their performance in practical applications. In this work, we employ a fiber electro-optical modulator driven by a voltage-controlled oscillator (VCO) to modulate a monochromatic laser and employ a second-harmonic generation process to convert it to the visible domain, where the beat note of the Raman operation laser is stabilized by controlling the output frequency of VCO with a digital phase-locked loop (PLL). The low-frequency phase noise is effectively suppressed compared to the scheme without active feedback and it reaches -80 dBc/Hz@5 kHz with a 20 kHz loop bandwidth. Furthermore, this compact and robust scheme effectively reduces the system’s complexity and cost, which is promising for extensive application in atomic, molecular, and optical physics. Phase-coherent multi-tone lasers play a critical role in atomic, molecular, and optical physics. Among them, the Raman opeartion laser for manipulating atomic hyperfine qubits requires gigahertz bandwidth and low phase noise to retain long-term coherence. Raman operation lasers generated by directly modulated and frequency-multipled infrared lasers are compact and stable but lack feedback control to actively suppress the phase noise, which limits their performance in practical applications. In this work, we employ a fiber electro-optical modulator driven by a voltage-controlled oscillator (VCO) to modulate a monochromatic laser and employ a second-harmonic generation process to convert it to the visible domain, where the beat note of the Raman operation laser is stabilized by controlling the output frequency of VCO with a digital phase-locked loop (PLL). The low-frequency phase noise is effectively suppressed compared to the scheme without active feedback and it reaches -80 dBc/Hz@5 kHz with a 20 kHz loop bandwidth. Furthermore, this compact and robust scheme effectively reduces the system’s complexity and cost, which is promising for extensive application in atomic, molecular, and optical physics.
Chinese Optics Letters
- Publication Date: Feb. 22, 2024
- Vol. 22, Issue 2, 022702 (2024)
Single-pixel 3D imaging based on fusion temporal data of single-photon detector and millimeter-wave radar
Tingqin Lai, Xiaolin Liang, Yi Zhu, Xinyi Wu, Lianye Liao, Xuelin Yuan, Ping Su, and Shihai Sun
Recently, there has been increased attention toward 3D imaging using single-pixel single-photon detection (also known as temporal data) due to its potential advantages in terms of cost and power efficiency. However, to eliminate the symmetry blur in the reconstructed images, a fixed background is required. This paper proposes a fusion-data-based 3D imaging method that utilizes a single-pixel single-photon detector and millimeter-wave radar to capture temporal histograms of a scene from multiple perspectives. Subsequently, the 3D information can be reconstructed from the one-dimensional fusion temporal data by using an artificial neural network. Both the simulation and experimental results demonstrate that our fusion method effectively eliminates symmetry blur and improves the quality of the reconstructed images. Recently, there has been increased attention toward 3D imaging using single-pixel single-photon detection (also known as temporal data) due to its potential advantages in terms of cost and power efficiency. However, to eliminate the symmetry blur in the reconstructed images, a fixed background is required. This paper proposes a fusion-data-based 3D imaging method that utilizes a single-pixel single-photon detector and millimeter-wave radar to capture temporal histograms of a scene from multiple perspectives. Subsequently, the 3D information can be reconstructed from the one-dimensional fusion temporal data by using an artificial neural network. Both the simulation and experimental results demonstrate that our fusion method effectively eliminates symmetry blur and improves the quality of the reconstructed images.
Chinese Optics Letters
- Publication Date: Feb. 27, 2024
- Vol. 22, Issue 2, 022701 (2024)
Ghost imaging, development, and recent advances [Invited]|On the Cover
Peiming Li, Xiaojin Chen, Xiaodong Qiu, Binglin Chen, Lixiang Chen, and Baoqing Sun
Ghost imaging (GI) is a novel imaging technique that has garnered widespread attention and discussion since its inception three decades ago. To this day, ghost imaging has become an effective bridge between the advantages of quantum light sources and the field of imaging. This article begins by tracing the origin of ghost imaging and reviewing its development journey. Subsequently, we introduce some recent and important achievements and research interests of the field, which mainly include two aspects. First, we review recent works that extend GI from the intensity-only target to the complex field domain, that is, ghost holography. Using quantum correlation, traditional holographic techniques have been reproduced at the single-photon level. Second, we review the recent development of GI with the implementation of the intensified charge-coupled device (ICCD). As detection efficiency improves, ghost imaging will gradually become an important platform for studying physical mechanisms and achieving quantum advantage in imaging. Ghost imaging (GI) is a novel imaging technique that has garnered widespread attention and discussion since its inception three decades ago. To this day, ghost imaging has become an effective bridge between the advantages of quantum light sources and the field of imaging. This article begins by tracing the origin of ghost imaging and reviewing its development journey. Subsequently, we introduce some recent and important achievements and research interests of the field, which mainly include two aspects. First, we review recent works that extend GI from the intensity-only target to the complex field domain, that is, ghost holography. Using quantum correlation, traditional holographic techniques have been reproduced at the single-photon level. Second, we review the recent development of GI with the implementation of the intensified charge-coupled device (ICCD). As detection efficiency improves, ghost imaging will gradually become an important platform for studying physical mechanisms and achieving quantum advantage in imaging.
Chinese Optics Letters
- Publication Date: Jul. 26, 2024
- Vol. 22, Issue 11, 112701 (2024)
Experimental realization of strong coupling between a cold atomic ensemble and an optical fiber microcavity
Li Li, Yu-Hao Pan, Yi-Jia Liu, Xiao-Long Zhou, Dong-Yu Huang, Ze-Min Shen, Jian Wang, Chuan-Feng Li, and Guang-Can Guo
The cavity quantum electrodynamics (QED) system is a promising platform for quantum optics and quantum information experiments. Its core is the strong coupling between atoms and optical cavity, which causes difficulty in the overlap between the atoms and the antinode of optical cavity mode. Here, we use a programmable movable optical dipole trap to load a cold atomic ensemble into an optical fiber microcavity and realize the strong coupling between the atoms and the optical cavity in which the coupling strength can be improved by polarization gradient cooling and adiabatic loading. By the measurement of vacuum Rabi splitting, the coupling strength can be as high as gN=2π×400 MHz, which means the effective atom number is Neff=16 and the collective cooperativity is CN=1466. These results show that this experimental system can be used for cold atomic ensemble and cold molecule based cavity QED research. The cavity quantum electrodynamics (QED) system is a promising platform for quantum optics and quantum information experiments. Its core is the strong coupling between atoms and optical cavity, which causes difficulty in the overlap between the atoms and the antinode of optical cavity mode. Here, we use a programmable movable optical dipole trap to load a cold atomic ensemble into an optical fiber microcavity and realize the strong coupling between the atoms and the optical cavity in which the coupling strength can be improved by polarization gradient cooling and adiabatic loading. By the measurement of vacuum Rabi splitting, the coupling strength can be as high as gN=2π×400 MHz, which means the effective atom number is Neff=16 and the collective cooperativity is CN=1466. These results show that this experimental system can be used for cold atomic ensemble and cold molecule based cavity QED research.
Chinese Optics Letters
- Publication Date: Aug. 18, 2023
- Vol. 21, Issue 9, 092702 (2023)
High-dimensional frequency conversion in a hot atomic system
Weihang Zhang, Yinghao Ye, Lei Zeng, Enze Li, Jingyuan Peng, Dongsheng Ding, and Baosen Shi
One of the major difficulties in realizing a high-dimensional frequency converter for conventional optical vortex (COV) modes stems from the difference in ring diameter of the COV modes with different topological charge numbers l. Here, we implement a high-dimensional frequency converter for perfect optical vortex (POV) modes with invariant sizes by way of the four-wave mixing (FWM) process using Bessel–Gaussian beams instead of Laguerre–Gaussian beams. The measured conversion efficiency from 1530 to 795 nm is independent of l at least in subspace l∈{-6,…,6}, and the achieved conversion fidelities for two-dimensional (2D) superposed POV states exceed 97%. We further realize the frequency conversion of 3D, 5D, and 7D superposition states with fidelities as high as 96.70%, 89.16%, and 88.68%, respectively. The proposed scheme is implemented in hot atomic vapor. It is also compatible with the cold atomic system and may find applications in high-capacity and long-distance quantum communication. One of the major difficulties in realizing a high-dimensional frequency converter for conventional optical vortex (COV) modes stems from the difference in ring diameter of the COV modes with different topological charge numbers l. Here, we implement a high-dimensional frequency converter for perfect optical vortex (POV) modes with invariant sizes by way of the four-wave mixing (FWM) process using Bessel–Gaussian beams instead of Laguerre–Gaussian beams. The measured conversion efficiency from 1530 to 795 nm is independent of l at least in subspace l∈{-6,…,6}, and the achieved conversion fidelities for two-dimensional (2D) superposed POV states exceed 97%. We further realize the frequency conversion of 3D, 5D, and 7D superposition states with fidelities as high as 96.70%, 89.16%, and 88.68%, respectively. The proposed scheme is implemented in hot atomic vapor. It is also compatible with the cold atomic system and may find applications in high-capacity and long-distance quantum communication.
Chinese Optics Letters
- Publication Date: Aug. 15, 2023
- Vol. 21, Issue 9, 092701 (2023)
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