Photon quantum statistics of light can be shown by the high-order coherence. The fourth-order coherences of various quantum states including Fock states, coherent states, thermal states and squeezed vacuum states are ...Photon quantum statistics of light can be shown by the high-order coherence. The fourth-order coherences of various quantum states including Fock states, coherent states, thermal states and squeezed vacuum states are investigated based on a double Hanbury Brown Twiss （HBT） scheme. The analytical results are obtained by taking the overall efficiency and background into account.展开更多
We experimentally demonstrate real-time detection of individual cesium atoms by using a high-finesse optical micro-cavity in a strong coupling regime.A cloud of cesium atoms is trapped in a magneto-optical trap positi...We experimentally demonstrate real-time detection of individual cesium atoms by using a high-finesse optical micro-cavity in a strong coupling regime.A cloud of cesium atoms is trapped in a magneto-optical trap positioned at 5mm above the micro-cavity center.The atoms fall down freely in gravitation after shutting off the magnetooptical trap and pass through the cavity.The cavity transmission is strongly affected by the atoms in the cavity,which enables the micro-cavity to sense the atoms individually.We detect the single atom transits either in the resonance or various detunings.The single atom vacuum-Rabi splitting is directly measured to beΩ=2π×23.9 MHz.The average duration of atom-cavity coupling of about 110μs is obtained according to the probability distribution of the atom transits.展开更多
We report the experimental generation of a squeezed vacuum at frequencies ranging from 2.5 kHz to 200 kHz that is resonant on the cesium D2 line by using a below-threshold optical parametric oscillator （OPO）. The OP...We report the experimental generation of a squeezed vacuum at frequencies ranging from 2.5 kHz to 200 kHz that is resonant on the cesium D2 line by using a below-threshold optical parametric oscillator （OPO）. The OPO is based on a periodically-poled KTiOPO4 （PPKTP） crystal that is pumped using a bow-tie four-mirror ring frequency doubler. The phase of the squeezed light is controlled using a quantum noise locking technique. At a pump power of 115 mW, maximum quadrature phase squeezing of 3.5 dB and anti-squeezing of 7.5 dB are detected using a home-made balanced homodyne detector. This squeezed vacuum at an atomic transition in the kilohertz range is an ideal quantum source for quantum metrology of enhancing measurement precision, especially for ultra-sensitive measurement of weak magnetic fields when using a Cs atomic magnetometer in the audio frequency range.展开更多
Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth(MRL),is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper...Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth(MRL),is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper, we have extensively studied how the pump intensity affects the spin relaxation. The experiment is performed with a cesium vapor cell, and the influence of the pump intensity on MRL is measured at room temperature at zero-field resonance. A simple model with five atomic levels of a Λ-like configuration is discussed theoretically, which can be used to represent the experimental process approximately, and the experimental results can be explained to some extent. Both the experimental and the theoretical results show a nonlinear broadening of the MRL when the pump intensity is increasing. The work helps to understand the mechanism of pump induced atomic spin relaxation in the atomic magnetometers.展开更多
The second-order degree of coherence of pseudo-thermal light and coherence time are experimentally studied via the Hanbruy-Brown-Twiss （HBT） scheme. The system consists of two non-photon-number-resolving single- pho...The second-order degree of coherence of pseudo-thermal light and coherence time are experimentally studied via the Hanbruy-Brown-Twiss （HBT） scheme. The system consists of two non-photon-number-resolving single- photon-counting modules （SPCMs） operating in the Geiger mode. We investigate the coherence time of the incident beam for different spot sizes on a ground glass a^d speeds of a rotating ground glass. The corresponding coherence time can be obtained from Gaussian fitting for the measured second-order degree of coherence. The results show that the coherence time of measured pseudo-thermal light depends on the spot sizes and the rotating speeds of the ground glass. The maximum value of the second-order degree of coherence is reduced as the rotating speed decreases. This result can be well explained by the model of mixed thermal and coherent fields with different ratios.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974125,60821004,60808006,60978017 and 60578018)the State Basic Key Research Program of China(Grant No.2006CB921102)
文摘Photon quantum statistics of light can be shown by the high-order coherence. The fourth-order coherences of various quantum states including Fock states, coherent states, thermal states and squeezed vacuum states are investigated based on a double Hanbury Brown Twiss （HBT） scheme. The analytical results are obtained by taking the overall efficiency and background into account.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10794125,60808006,60821004,61078051 and 60978017.
文摘We experimentally demonstrate real-time detection of individual cesium atoms by using a high-finesse optical micro-cavity in a strong coupling regime.A cloud of cesium atoms is trapped in a magneto-optical trap positioned at 5mm above the micro-cavity center.The atoms fall down freely in gravitation after shutting off the magnetooptical trap and pass through the cavity.The cavity transmission is strongly affected by the atoms in the cavity,which enables the micro-cavity to sense the atoms individually.We detect the single atom transits either in the resonance or various detunings.The single atom vacuum-Rabi splitting is directly measured to beΩ=2π×23.9 MHz.The average duration of atom-cavity coupling of about 110μs is obtained according to the probability distribution of the atom transits.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11634008,61227902,11574187,and 11674203)the National Key Research and Development Program of China(Grant No.2017YFA0304500)the Fund of“1331 Project”Key Subjects Construction of Shanxi Province,China
文摘We report the experimental generation of a squeezed vacuum at frequencies ranging from 2.5 kHz to 200 kHz that is resonant on the cesium D2 line by using a below-threshold optical parametric oscillator （OPO）. The OPO is based on a periodically-poled KTiOPO4 （PPKTP） crystal that is pumped using a bow-tie four-mirror ring frequency doubler. The phase of the squeezed light is controlled using a quantum noise locking technique. At a pump power of 115 mW, maximum quadrature phase squeezing of 3.5 dB and anti-squeezing of 7.5 dB are detected using a home-made balanced homodyne detector. This squeezed vacuum at an atomic transition in the kilohertz range is an ideal quantum source for quantum metrology of enhancing measurement precision, especially for ultra-sensitive measurement of weak magnetic fields when using a Cs atomic magnetometer in the audio frequency range.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0304502)the National Natural Science Foundation of China(Grant Nos.11634008,11674203,11574187,and 61227902)
文摘Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth(MRL),is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper, we have extensively studied how the pump intensity affects the spin relaxation. The experiment is performed with a cesium vapor cell, and the influence of the pump intensity on MRL is measured at room temperature at zero-field resonance. A simple model with five atomic levels of a Λ-like configuration is discussed theoretically, which can be used to represent the experimental process approximately, and the experimental results can be explained to some extent. Both the experimental and the theoretical results show a nonlinear broadening of the MRL when the pump intensity is increasing. The work helps to understand the mechanism of pump induced atomic spin relaxation in the atomic magnetometers.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60578018, 60808006 and 60821004, the National Basic Research Program of China under Grant No 2006CB921102, the Research Funds for Returned Scholar Abroad and Youth Science and Technology from Shanxi Province （2008021003）, and Star Special Project of Shanxi Province （08121019）.
文摘The second-order degree of coherence of pseudo-thermal light and coherence time are experimentally studied via the Hanbruy-Brown-Twiss （HBT） scheme. The system consists of two non-photon-number-resolving single- photon-counting modules （SPCMs） operating in the Geiger mode. We investigate the coherence time of the incident beam for different spot sizes on a ground glass a^d speeds of a rotating ground glass. The corresponding coherence time can be obtained from Gaussian fitting for the measured second-order degree of coherence. The results show that the coherence time of measured pseudo-thermal light depends on the spot sizes and the rotating speeds of the ground glass. The maximum value of the second-order degree of coherence is reduced as the rotating speed decreases. This result can be well explained by the model of mixed thermal and coherent fields with different ratios.
