Dependence of Rydberg-atom-based sensor performance on different Rydberg atom populations in one atomic-vapor cell

The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions,that is,the same atomic population density and buffer gas pressure,which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations.Here,utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure,the height and full width at half maximum of electromagnetically induced transparency(EIT)signal,and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies(saturated laser power).It is identified that EIT signal height is proportional to the cell length,full width at half maximum and sensitivity grow with the increment of cell length to a certain extent.Employing the coherent integration signal theory and atomic linear expansion coefficient method,theoretical analysis of the EIT height and sensitivity are further investigated.The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement,communication,and imaging.

Atomic population distribution of excited states in He electrodeless discharge lamp

Population ratios between excited states are measured to build the excited state Faraday anomalous dispersion optical filter(ESFADOF). We calculate these values between the excited states according to the spontaneous transition probabilities using rate equations and the measured intensities of fluorescence spectral lines of He atoms in an electrodeless discharge lamp in the visible spectral region from 350 to 730 nm. The electrodeless discharge lamp with populations in excited states can be used to realize the frequency stabilization reference of the laser frequency standard. This lamp can also build ESFADOFs for submarine communication application in the blue-green wavelength to simplify the system without the use of a pump laser.

Measurements of Majorana transition frequency shift in caesium atomic fountain clocks

The caesium atomic fountain clock is a primary frequency standard.During its operation,a Majorana transition frequency shift will occur once a magnetic field at some special locations along the atomic trajectory is singular.In this study,by developing a physical model,we analyzed the magnetic field requirements for atomic adiabatic transition and calculated the influence of the Majorana atomic transition on the atomic state via a quantum method.Based on the simulation results for the magnetic field in the fountain clock,we applied the Monte Carlo method to simulate the relationship between the Majorana transition frequency shift and the magnetic field at the entrance of the magnetic shielding,as well as the initial atomic population.Measurement of the Majorana transition frequency shift was realized by state-selecting asymmetrically populated atoms.The relationship between the Majorana transition frequency shift and the axial magnetic field at the entrance of the magnetic shielding was obtained.The measured results were essentially consistent with the calculated results.Thus,the magnetic field at the entrance of the magnetic shielding was configured,and the Majorana transition frequency shift of the fountain clock was calculated to be 4.57×10^(-18).

Stable ^(85)Rb micro vapour cells:fabrication based on anodic bonding and application in chip-scale atomic clocks

We describe the microfabrication of ^85Rb vapour cells using a glass-silicon anodic bonding technique and in situ chemical reaction between rubidium chloride and barium azide to produce Rb. Under controlled conditions, the pure metallic Rb drops and buffer gases were obtained in the cells with a few mm^3 internal volumes during the cell sealing process. At an ambient temperature of 90 ℃ the optical absorption resonance of ^85Rb D1 transition with proper broadening and the corresponding coherent population trapping （CPT） resonance, with a signal contrast of 1.5% and linewidth of about 1.7 kHz, have been detected. The sealing quality and the stability of the cells have also been demonstrated experimentally by using the helium leaking detection and the after-9-month optoelectronics measurement which shows a similar CPT signal as its original status. In addition, the physics package of chip-scale atomic clock （CSAC） based on the cell was realized. The measured frequency stability of the physics package can reach to 2.1 × 10^-10 at one second when the cell was heated to 100 ℃ which proved that the cell has the quality to be used in portable and battery-operated devices.

Coherent population trapping magnetometer by differential detecting magneto–optic rotation effect

A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.

Population dynamics of excited atoms in non-Markovian environments at zero and finite temperature

The population dynamics of a two-atom system, which is in two independent Lorentzian reservoirs or in two independent Ohmic reservoirs respectively, where the reservoirs are at zero temperature or finite temperature, is studied by using the time-convolutionless master-equation method. The influences of the characteristics and temperature of a non-Markovian environment on the population of the excited atoms are analyzed. We find that the population trapping of the excited atoms is related to the characteristics and the temperature of the non-Markovian environment. The results show that, at zero temperature, the two atoms can be effectively trapped in the excited state both in the Lorentzian reservoirs and in the Ohmic reservoirs. At finite temperature, the population of the excited atoms will quickly decay to a nonzero value.