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Dive into the research topics where Xianxin Guo is active.

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Featured researches published by Xianxin Guo.


Physical Review Letters | 2015

Measuring the biphoton temporal wave function with polarization-dependent and time-resolved two-photon interference.

Peng Chen; Chi Shu; Xianxin Guo; Michael Ming-tak Loy; Shengwang Du

We describe and demonstrate a quantum state tomography for measuring the complex temporal waveform of narrowband biphotons. Through six sets of two-photon interference measurements projected in different polarization subspaces, we can construct the time-frequency entangled twophoton joint amplitude and phase functions in continuous-variable time domain. For the first time, we apply this technique to experimentally determine the temporal quantum states of narrowband biphotons generated from spontaneous four-wave mixing in cold atoms, and fully confirm the theoretical predictions.


Physical Review Letters | 2015

Shaping the Biphoton Temporal Waveform with Spatial Light Modulation

Luwei Zhao; Xianxin Guo; Yuan Sun; Yumian Su; Michael Ming-tak Loy; Shengwang Du

We demonstrate a technique for shaping the temporal wave function of biphotons generated from spatially modulated spontaneous four-wave mixing in cold atoms. We show that the spatial profile of the pump field can be mapped onto the biphoton temporal wave function in the group delay regime. The spatial profile of the pump laser beam is shaped by using a spatial light modulator. This spatial-to-temporal mapping enables the generation of narrow-band biphotons with controllable temporal waveforms.


Physical Review A | 2015

Narrowband Biphotons with Polarization-frequency Coupled Hyperentanglement

Chi Shu; Xianxin Guo; Peng Chen; M. M. T. Loy; Shengwang Du

DepartmentofPhysics,TheHongKongUniversityofScienceandTechnology,ClearWaterBay,Kowloon,HongKong,China(Dated: January 26, 2015)We demonstrate the generation of narrowband biphotons with polarization-frequency coupled hy-perentanglement from spontaneous four-wave mixing in cold atoms. The coupling between polariza-tion and frequency is realized through a frequency shifter and linear optics. When the polarization-frequency degrees of freedom are decoupled, it is robust to create polarization and frequency Bellstates, confirmed by the polarization quantum-state tomography and the two-photon temporal quan-tum beating. Making use of the polarization-frequency coupling to transfer polarization phase retardto the entangled frequency modes, we produce a frequency Bell state with tunable phase differencebetween its two bases.


Applied Physics Letters | 2017

Bright narrowband biphoton generation from a hot rubidium atomic vapor cell

Lingbang Zhu; Xianxin Guo; Chi Shu; Heejeong Jeong; Shengwang Du

We demonstrate the generation of high-quality narrowband biphotons from a Doppler-broadened hot rubidium atomic vapor cell. Choosing a double-Λ atomic energy level scheme for optimizing both spontaneous four-wave mixing nonlinear parametric interaction and electromagnetically induced transparency (EIT), we achieve a biphoton spectral brightness as high as 14 000 s−1 MHz−1. Meanwhile, we apply a spatially tailored optical pumping beam for reduction of the Raman noise and obtain a violation of the Cauchy-Schwarz inequality by a factor of 1023.


arXiv: Quantum Physics | 2017

Testing the Bell inequality on frequency-bin entangled photon pairs using time-resolved detection

Xianxin Guo; Yefeng Mei; Shengwang Du

Entanglement, describing the inseparability of a quantum multiparty system, is one of the most intriguing features of quantum mechanics. Violation of Bell inequality, for ruling out the possibility of local hidden-variable theories, is commonly used as a strong witness of quantum entanglement. In previous Bell test experiments with photonic entanglement based on two-photon coincidence measurement, the photon temporal wave packets were absorbed completely by the detectors. That is, the photon coherence time is much shorter than the detection time window. Here we demonstrate the generation of frequency-bin entangled narrowband biphotons, and for the first time, to the best of our knowledge, test the Clauser–Horne–Shimony–Holt (CHSH) Bell inequality |S|≤2 for their nonlocal temporal correlations with time-resolved detection. We obtain a maximum |S| value of 2.52±0.48, which violates the CHSH inequality. Our result will have applications in quantum information processing involving time-frequency entanglement.


Physical Review Letters | 2017

Quantum Heat Engine Using Electromagnetically Induced Transparency

Yueyang Zou; Yue Jiang; Yefeng Mei; Xianxin Guo; Shengwang Du

We report an experiment demonstrating the generation of directional thermal radiation with a spectral brightness that is about 9 times greater than that of the ambient pumping reservoir. The experiment is based on the recent proposal for a nontraditional quantum heat engine and uses cold Rb atoms, electromagnetically induced transparency, and photon correlation spectroscopy [Phys. Rev. A 94, 053859 (2016)PLRAAN2469-992610.1103/PhysRevA.94.053859].


Optica | 2015

Frequency-induced phase-tunable polarization-entangled narrowband biphotons

Peng Chen; Xianxin Guo; Chi Shu; Michael Ming-tak Loy; Shengwang Du

Manipulating polarization entanglement of paired photons is always of great interest for understanding the quantum nature of photons and exploring their applications in quantum information processing and quantum communication. Narrowband biphotons with polarization entanglement are especially important for a quantum network based on efficient photon–atom interactions. In most demonstrated cases, the polarization-entangled states are manipulated through the birefringent effect. In this Letter, we produce narrowband polarization-entangled biphotons from spontaneous four-wave mixing in cold atoms and demonstrate a new method to tune the phase of the polarization entanglement by varying the frequency of one of the classical driving lasers. This is achieved through two-photon interference with a path-exchange symmetry. Our result represents a precision control of polarization entanglement from the frequency domain, and may have promising applications in quantum information and precision measurement.


Physical Review Letters | 2017

Mirrorless Optical Parametric Oscillation with Tunable Threshold in Cold Atoms

Yefeng Mei; Xianxin Guo; Luwei Zhao; Shengwang Du

We report the demonstration of a mirrorless optical parametric oscillator with a tunable threshold in laser-cooled atoms with four-wave mixing (FWM) using electromagnetically induced transparency. Driven by two classical laser beams, the generated Stokes and anti-Stokes fields counterpropagate and build up efficient intrinsic feedback through the nonlinear FWM process. This feedback does not involve any cavity or spatially distributed microstructures. We observe the transition of photon correlation properties from the biphoton quantum regime (below the threshold) to the oscillation regime (above the threshold). The pump threshold can be tuned by varying the operating parameters. We achieve the oscillation with a threshold as low as 15  μW.


Journal of Optics | 2015

Frequency-Bin Entanglement with Tunable Phase

Xianxin Guo; Peng Chen; Chi Shu; Michael Ming-tak Loy; Shengwang Du

We describe a technique to produce narrow-band photon pairs with frequency-bin entanglement, whose relative phase can be tuned using linear polarization optics. We show that, making use of the polarization-frequency coupling effect, the phase of a complex polarizer can be transferred into the frequency entanglement.


Optica | 2014

Photon Pairs With Coherence Time Exceeding 1 μs

Luwei Zhao; Xianxin Guo; Chang Liu; Yuan Sun; Michael Ming-tak Loy; Shengwang Du

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Shengwang Du

Hong Kong University of Science and Technology

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Chi Shu

Hong Kong University of Science and Technology

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Yefeng Mei

Hong Kong University of Science and Technology

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Luwei Zhao

Hong Kong University of Science and Technology

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M. M. T. Loy

Hong Kong University of Science and Technology

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Michael Ming-tak Loy

Hong Kong University of Science and Technology

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Yuan Sun

Hong Kong University of Science and Technology

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Lingbang Zhu

Hong Kong University of Science and Technology

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