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Quantum Optics and Quantum Information|29 Article(s)
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)
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)
Surpassing the standard quantum limit of optical imaging via deep learning
Miao Cai, Zhi-Xiang Li, Hao-Dong Wu, Ya-Ping Ruan, Lei Tang, Jiang-Shan Tang, Ming-Yuan Chen, Han Zhang, Ke-Yu Xia, Min Xiao, and Yan-Qing Lu
The sensitivity of optical measurement is ultimately constrained by the shot noise to the standard quantum limit. It has become a common concept that beating this limit requires quantum resources. A deep-learning neural network free of quantum principle has the capability of removing classical noise from images, but it is unclear in reducing quantum noise. In a coincidence-imaging experiment, we show that quantum-resource-free deep learning can be exploited to surpass the standard quantum limit via the photon-number-dependent nonlinear feedback during training. Using an effective classical light with photon flux of about 9×104 photons per second, our deep-learning-based scheme achieves a 14 dB improvement in signal-to-noise ratio with respect to the standard quantum limit. The sensitivity of optical measurement is ultimately constrained by the shot noise to the standard quantum limit. It has become a common concept that beating this limit requires quantum resources. A deep-learning neural network free of quantum principle has the capability of removing classical noise from images, but it is unclear in reducing quantum noise. In a coincidence-imaging experiment, we show that quantum-resource-free deep learning can be exploited to surpass the standard quantum limit via the photon-number-dependent nonlinear feedback during training. Using an effective classical light with photon flux of about 9×104 photons per second, our deep-learning-based scheme achieves a 14 dB improvement in signal-to-noise ratio with respect to the standard quantum limit.
Chinese Optics Letters
- Publication Date: Aug. 08, 2023
- Vol. 21, Issue 8, 082701 (2023)
Shape-preserving storage of elegant Ince-Gaussian modes in warm atomic vapor
Zehao Shen, Chengyuan Wang, Yun Chen, Qifan Wu, Ye Yang, Xin Yang, Hong Gao, and Fuli Li
Multimode photonic quantum memory could enhance the information processing speed in a quantum repeater-based quantum network. A large obstacle that impedes the storage of the spatial multimode in a hot atomic ensemble is atomic diffusion, which severely disturbs the structure of the retrieved light field. In this paper, we demonstrate that the elegant Ince-Gaussian (eIG) mode possesses the ability to resist such diffusion. Our experimental results show that the overall structure of the eIG modes under different parameters maintains well after microseconds of storage. In contrast, the standard IG modes under the same circumstance are disrupted and become unrecognizable. Our findings could promote the construction of quantum networks based on room-temperature atoms. Multimode photonic quantum memory could enhance the information processing speed in a quantum repeater-based quantum network. A large obstacle that impedes the storage of the spatial multimode in a hot atomic ensemble is atomic diffusion, which severely disturbs the structure of the retrieved light field. In this paper, we demonstrate that the elegant Ince-Gaussian (eIG) mode possesses the ability to resist such diffusion. Our experimental results show that the overall structure of the eIG modes under different parameters maintains well after microseconds of storage. In contrast, the standard IG modes under the same circumstance are disrupted and become unrecognizable. Our findings could promote the construction of quantum networks based on room-temperature atoms.
Chinese Optics Letters
- Publication Date: Jul. 11, 2023
- Vol. 21, Issue 7, 072701 (2023)
Satellite-to-aircraft quantum key distribution performance estimation with boundary layer effects
Huicun Yu, Bangying Tang, Jiahao Li, Yuexiang Cao, Han Zhou, Sichen Li, Haoxi Xiong, Bo Liu, and Lei Shi
Remarkable progress has been made in satellite-based quantum key distribution (QKD), which can effectively provide QKD service even at the intercontinental scale and construct an ultralong-distance global quantum network. But there are still some places where terrestrial fiber and ground stations cannot be constructed, like harsh mountainous areas and air space above the sea. So the airborne platform is expected to replace the ground station and provide flexible and relay links for the large-scale integrated communication network. However, the photon transmission rate would be randomly reduced, owing to the randomly distributed boundary layer that surrounds the surface of the aircraft when the flight speed is larger than 0.3 Ma. Previous research of airborne QKD with boundary layer effects is mainly under the air-to-ground scenario in which the aircraft is a transmitter, while the satellite-to-aircraft scenario is rarely reported. In this article, we propose a performance evaluation scheme of satellite-to-aircraft QKD with boundary layer effects in which the aircraft is the receiver. With common experimental settings, the boundary layer would introduce a ∼31 dB loss to the transmitted photons, decrease ∼47% of the quantum communication time, and decrease ∼51% of the secure key rate, which shows that the aero-optical effects caused by the boundary layer cannot be ignored. Our study can be performed in future airborne quantum communication designs. Remarkable progress has been made in satellite-based quantum key distribution (QKD), which can effectively provide QKD service even at the intercontinental scale and construct an ultralong-distance global quantum network. But there are still some places where terrestrial fiber and ground stations cannot be constructed, like harsh mountainous areas and air space above the sea. So the airborne platform is expected to replace the ground station and provide flexible and relay links for the large-scale integrated communication network. However, the photon transmission rate would be randomly reduced, owing to the randomly distributed boundary layer that surrounds the surface of the aircraft when the flight speed is larger than 0.3 Ma. Previous research of airborne QKD with boundary layer effects is mainly under the air-to-ground scenario in which the aircraft is a transmitter, while the satellite-to-aircraft scenario is rarely reported. In this article, we propose a performance evaluation scheme of satellite-to-aircraft QKD with boundary layer effects in which the aircraft is the receiver. With common experimental settings, the boundary layer would introduce a ∼31 dB loss to the transmitted photons, decrease ∼47% of the quantum communication time, and decrease ∼51% of the secure key rate, which shows that the aero-optical effects caused by the boundary layer cannot be ignored. Our study can be performed in future airborne quantum communication designs.
Chinese Optics Letters
- Publication Date: Mar. 24, 2023
- Vol. 21, Issue 4, 042702 (2023)
Photon pair generation in lithium niobate waveguide periodically poled by femtosecond laser|On the Cover
Fan Dai, Qianqian Tian, Shuangyin Huang, Min Wang, Chenghou Tu, Yan Sheng, Yongnan Li, and Hui-Tian Wang
Reliable generation of single photons is of key importance for fundamental physical experiments and quantum protocols. The periodically poled lithium niobate (LN) waveguide has shown promise for an integrated quantum source due to its large spectral tunability and high efficiency, benefiting from the quasi-phase-matching. Here we demonstrate photon-pair sources based on an LN waveguide periodically poled by a tightly focused femtosecond laser beam. The pair coincidence rate reaches ∼8000 counts per second for average pump power of 3.2 mW (peak power is 2.9 kW). Our results prove the possibility of application of the nonlinear photonics structure fabricated by femtosecond laser to the integrated quantum source. This method can be extended to three-dimensional domain structures, which provide a potential platform for steering the spatial degree of freedom of the entangled two-photon states. Reliable generation of single photons is of key importance for fundamental physical experiments and quantum protocols. The periodically poled lithium niobate (LN) waveguide has shown promise for an integrated quantum source due to its large spectral tunability and high efficiency, benefiting from the quasi-phase-matching. Here we demonstrate photon-pair sources based on an LN waveguide periodically poled by a tightly focused femtosecond laser beam. The pair coincidence rate reaches ∼8000 counts per second for average pump power of 3.2 mW (peak power is 2.9 kW). Our results prove the possibility of application of the nonlinear photonics structure fabricated by femtosecond laser to the integrated quantum source. This method can be extended to three-dimensional domain structures, which provide a potential platform for steering the spatial degree of freedom of the entangled two-photon states.
Chinese Optics Letters
- Publication Date: Apr. 06, 2023
- Vol. 21, Issue 4, 042701 (2023)
All-fiber telecom band energy-time entangled biphoton source|Editors' Pick
Yuting Liu, Junjie Xing, Zhiguang Xia, Run'ai Quan, Huibo Hong, Tao Liu, Shougang Zhang, Xiao Xiang, and Ruifang Dong
We report an all-fiber telecom-band energy-time entangled biphoton source with all physical elements integrated into a compact cabinet. At a pump power of 800 µW, the photon pairs generation rate reaches 6.9 MHz with the coincidence-to-accidental ratio (CAR) better than 1150. The long-term stability of the biphoton source is characterized by measuring the Hong–Ou–Mandel interference visibility and CAR within a continuous operation period of more than 10 h. Benefiting from the advantages of compact size, light weight, and high stability, this device provides a convenient resource for various field turnkey quantum communication and metrology applications. We report an all-fiber telecom-band energy-time entangled biphoton source with all physical elements integrated into a compact cabinet. At a pump power of 800 µW, the photon pairs generation rate reaches 6.9 MHz with the coincidence-to-accidental ratio (CAR) better than 1150. The long-term stability of the biphoton source is characterized by measuring the Hong–Ou–Mandel interference visibility and CAR within a continuous operation period of more than 10 h. Benefiting from the advantages of compact size, light weight, and high stability, this device provides a convenient resource for various field turnkey quantum communication and metrology applications.
Chinese Optics Letters
- Publication Date: Mar. 14, 2023
- Vol. 21, Issue 3, 032701 (2023)
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