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Quantum optics|35 Article(s)
Detection of 13.8 dB squeezed vacuum states by optimizing the interference efficiency and gain of balanced homodyne detection
Xiaocong Sun, Yajun Wang, Long Tian, Yaohui Zheng, and Kunchi Peng
Squeezed states belong to the most prominent non-classical resources. They have compelling applications in precise measurement, quantum computation, and detection. Here, we report on the direct measurement of 13.8 dB squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection. By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%. The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor (JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector. Squeezed states belong to the most prominent non-classical resources. They have compelling applications in precise measurement, quantum computation, and detection. Here, we report on the direct measurement of 13.8 dB squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection. By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%. The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor (JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector.
Chinese Optics Letters
- Publication Date: Jul. 10, 2019
- Vol. 17, Issue 7, 072701 (2019)
Experimental observations of boundary conditions of continuous-time quantum walks
Xiaochuan Han, Lantian Feng, Yuxuan Li, Lanxuan Zhang, Junfeng Song, and Yongsheng Zhang
The continuous-time quantum walk (CTQW) is the quantum analogue of the continuous-time classical walk and is widely used in universal quantum computations. Here, taking the advantages of the waveguide arrays, we implement large-scale CTQWs on chips. We couple the single-photon source into the middle port of the waveguide arrays and measure the emergent photon number distributions by utilizing the fiber coupling platform. Subsequently, we simulate the photon number distributions of the waveguide arrays by considering the boundary conditions. The boundary conditions are quite necessary in solving the problems of quantum mazes. The continuous-time quantum walk (CTQW) is the quantum analogue of the continuous-time classical walk and is widely used in universal quantum computations. Here, taking the advantages of the waveguide arrays, we implement large-scale CTQWs on chips. We couple the single-photon source into the middle port of the waveguide arrays and measure the emergent photon number distributions by utilizing the fiber coupling platform. Subsequently, we simulate the photon number distributions of the waveguide arrays by considering the boundary conditions. The boundary conditions are quite necessary in solving the problems of quantum mazes.
Chinese Optics Letters
- Publication Date: May. 10, 2019
- Vol. 17, Issue 5, 052701 (2019)
Enhancing coupling coefficient in a hybrid nanotoroid–nanowire system|Editors' Pick
Qi Zhang, Juanjuan Ren, Xueke Duan, He Hao, Qihuang Gong, and Ying Gu
Enhancing light–matter interaction in cavity quantum electrodynamics has aroused widespread interests in on-chip quantum information processing. Here, we propose a hybrid nanotoroid–nanowire system to enhance photon–exciton interaction. A nanoscale gap is formed by placing a dielectric nanowire close to a dielectric nanotoroid, where the coupling coefficient between photon and emitter can achieve 5.55 times of that without nanogap. Meanwhile, the cavity loss and spontaneous emission of the emitter will remain at a small value to guarantee the realization of strong coupling. The method might hold promise for the research of nanophotonics, quantum optics, and novel optical devices. Enhancing light–matter interaction in cavity quantum electrodynamics has aroused widespread interests in on-chip quantum information processing. Here, we propose a hybrid nanotoroid–nanowire system to enhance photon–exciton interaction. A nanoscale gap is formed by placing a dielectric nanowire close to a dielectric nanotoroid, where the coupling coefficient between photon and emitter can achieve 5.55 times of that without nanogap. Meanwhile, the cavity loss and spontaneous emission of the emitter will remain at a small value to guarantee the realization of strong coupling. The method might hold promise for the research of nanophotonics, quantum optics, and novel optical devices.
Chinese Optics Letters
- Publication Date: Mar. 10, 2019
- Vol. 17, Issue 3, 032702 (2019)
Space–time cloaks through birefringent Goos–Hänchen shifts
Humayun Khan, Muhammad Haneef, and Bakhtawar
We report a theoretical demonstration for the creation of space–time holes based on birefringence of reflection, transmission, and the Goos–H chen (GH) shifts from a chiral medium. We observed space–time holes in the reflection, transmission, and their corresponding GH-shifted beams. Two space–time holes are clearly detected in the regions of 0<t≤5τ0 and 5w≤y≤5w, as well as in the regions of 5τ0≤t≤0 and 5w≤y≤5w. These space–time holes hide objects and information contents from observers and hackers. The objects and information contents are completely undetectable, and thus events can be cloaked. The results of this paper have potential applications in the invisibility of drone technology and secure communication of information in telecom industries. We report a theoretical demonstration for the creation of space–time holes based on birefringence of reflection, transmission, and the Goos–H chen (GH) shifts from a chiral medium. We observed space–time holes in the reflection, transmission, and their corresponding GH-shifted beams. Two space–time holes are clearly detected in the regions of 0<t≤5τ0 and 5w≤y≤5w, as well as in the regions of 5τ0≤t≤0 and 5w≤y≤5w. These space–time holes hide objects and information contents from observers and hackers. The objects and information contents are completely undetectable, and thus events can be cloaked. The results of this paper have potential applications in the invisibility of drone technology and secure communication of information in telecom industries.
Chinese Optics Letters
- Publication Date: Mar. 10, 2019
- Vol. 17, Issue 3, 032701 (2019)
High efficiency continuous-variable quantum key distribution based on QC-LDPC codes
Ying Guo, Kangshuai Wang, Duan Huang, and Xueqin Jiang
Seeking good error correcting codes to improve the efficiency of continuous-variable quantum key distribution (CVQKD) reconciliation is a concerning issue. Due to the introduction of multidimensional reconciliation, the error correcting techniques in the classical binary-input additive white Gaussian noise channel are applicable to CVQKD. In this Letter, we apply the quasi-cyclic low-density parity-check (QC-LDPC) codes, which are specified in 5G protocol, to the reconciliation process. Simulation results show that the reconciliation efficiency can reach 92.6% when the code rate is 22/68 and the signal-to-noise ratio is 0.623. Such a new error correcting code points out a new direction for the development of CVQKD. Seeking good error correcting codes to improve the efficiency of continuous-variable quantum key distribution (CVQKD) reconciliation is a concerning issue. Due to the introduction of multidimensional reconciliation, the error correcting techniques in the classical binary-input additive white Gaussian noise channel are applicable to CVQKD. In this Letter, we apply the quasi-cyclic low-density parity-check (QC-LDPC) codes, which are specified in 5G protocol, to the reconciliation process. Simulation results show that the reconciliation efficiency can reach 92.6% when the code rate is 22/68 and the signal-to-noise ratio is 0.623. Such a new error correcting code points out a new direction for the development of CVQKD.
Chinese Optics Letters
- Publication Date: Nov. 10, 2019
- Vol. 17, Issue 11, 112701 (2019)
Improving the resolution in quantum and classical temporal imaging|Editors' Pick
Junheng Shi, Giuseppe Patera, Youzhen Gui, Mikhail I. Kolobov, Dmitri B. Horoshko, and Shensheng Han
The point-spread function of an optical system determines its optical resolution for both spatial and temporal imaging. For spatial imaging, it is given by a Fourier transform of the pupil function of the system. For temporal imaging based on nonlinear optical processes, such as sum-frequency generation or four-wave mixing, the point-spread function is related to the waveform of the pump wave by a nonlinear transformation. We compare the point-spread functions of three temporal imaging schemes: sum-frequency generation, co-propagating four-wave mixing, and counter-propagating four-wave mixing, and demonstrate that the last scheme provides the best temporal resolution. Our results are valid for both quantum and classical temporal imaging. The point-spread function of an optical system determines its optical resolution for both spatial and temporal imaging. For spatial imaging, it is given by a Fourier transform of the pupil function of the system. For temporal imaging based on nonlinear optical processes, such as sum-frequency generation or four-wave mixing, the point-spread function is related to the waveform of the pump wave by a nonlinear transformation. We compare the point-spread functions of three temporal imaging schemes: sum-frequency generation, co-propagating four-wave mixing, and counter-propagating four-wave mixing, and demonstrate that the last scheme provides the best temporal resolution. Our results are valid for both quantum and classical temporal imaging.
Chinese Optics Letters
- Publication Date: Sep. 10, 2018
- Vol. 16, Issue 9, 092701 (2018)
Multipartite entanglement generation with dipole induced transparency effect in indirectly coupled dipole-microcavity systems
Zhaohui Peng, Chunxia Jia, Yuqing Zhang, Zhonghua Zhu, and Xiaojuan Liu
We propose a feasible scheme of generating multipartite entanglement with the dipole induced transparency (DIT) effect in indirectly coupled dipole-microcavity systems. It is shown that the transmission spectrum is closely related with the interference of dipole-microcavity systems, and we can generate different classes of multipartite entanglement, e.g., the Greenberger–Horne–Zeilinger state, the W state, and the Dicke state, of the dipole emitters just by choosing an appropriate frequency of the incident photon. Benefiting from the DIT effect, the schemes may work in the bad or low-Q cavity regime only if the large Purcell factor of the dipole-microcavity system is fulfilled, and they are also insensitive to experimental noise, which may be feasible with present accessible technology. We propose a feasible scheme of generating multipartite entanglement with the dipole induced transparency (DIT) effect in indirectly coupled dipole-microcavity systems. It is shown that the transmission spectrum is closely related with the interference of dipole-microcavity systems, and we can generate different classes of multipartite entanglement, e.g., the Greenberger–Horne–Zeilinger state, the W state, and the Dicke state, of the dipole emitters just by choosing an appropriate frequency of the incident photon. Benefiting from the DIT effect, the schemes may work in the bad or low-Q cavity regime only if the large Purcell factor of the dipole-microcavity system is fulfilled, and they are also insensitive to experimental noise, which may be feasible with present accessible technology.
Chinese Optics Letters
- Publication Date: Aug. 10, 2018
- Vol. 16, Issue 8, 082702 (2018)
Efficient generation of non-classical photon pairs in a hot atomic ensemble
Chengyuan Wang, Yan Gu, Ya Yu, Dong Wei, Pei Zhang, Hong Gao, and Fuli Li
We demonstrate the generation of non-classical photon pairs in a warm Rb87 atomic vapor cell with no buffer gas or polarization preserving coatings via spontaneous four-wave mixing. We obtain the photon pairs with a 1/e correlation time of 40 ns and the violation of Cauchy–Schwartz inequality by a factor of 23±3. This provides a convenient and efficient method to generate photon pair sources based on an atomic ensemble. We demonstrate the generation of non-classical photon pairs in a warm Rb87 atomic vapor cell with no buffer gas or polarization preserving coatings via spontaneous four-wave mixing. We obtain the photon pairs with a 1/e correlation time of 40 ns and the violation of Cauchy–Schwartz inequality by a factor of 23±3. This provides a convenient and efficient method to generate photon pair sources based on an atomic ensemble.
Chinese Optics Letters
- Publication Date: Aug. 10, 2018
- Vol. 16, Issue 8, 082701 (2018)
Generation of intensity difference squeezed state at a wavelength of 1.34 μm
Meiru Huo, Jiliang Qin, Yingrong Sun, Zhihui Yan, and Xiaojun Jia
The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO4 crystal operates above the threshold, an intensity difference squeezed state at a telecommunication wavelength can be obtained. The squeezing of 7.7±0.5 dB below the SNL is achieved in an analysis frequency region of 2.4–5.0 MHz. The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO4 crystal operates above the threshold, an intensity difference squeezed state at a telecommunication wavelength can be obtained. The squeezing of 7.7±0.5 dB below the SNL is achieved in an analysis frequency region of 2.4–5.0 MHz.
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 052701 (2018)
Controllable single-photon transport in an optical waveguide coupled to an optomechanical cavity with a V-type three-level atom
Yuqing Zhang, Zhonghua Zhu, Zhaohui Peng, Chunlei Jiang, Yifeng Chai, and Lei Tan
An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect, the coupling strengths between the cavity and the atom or the waveguide, and the atomic dissipation on the single-photon transport properties are analyzed systematically. Interestingly, the single-photon transmission spectra show multiple double electromagnetically induced transparency. Moreover, the double electromagnetically induced transparency can be switched to a single one by tuning the atom–cavity detuning. An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect, the coupling strengths between the cavity and the atom or the waveguide, and the atomic dissipation on the single-photon transport properties are analyzed systematically. Interestingly, the single-photon transmission spectra show multiple double electromagnetically induced transparency. Moreover, the double electromagnetically induced transparency can be switched to a single one by tuning the atom–cavity detuning.
Chinese Optics Letters
- Publication Date: Jan. 10, 2018
- Vol. 16, Issue 1, 012701 (2018)
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