Runbing Li

Measurement of the quadratic Zeeman shift of 85Rb hyperfine sublevels using stimulated Raman transitions

We demonstrate a technique for directly measuring the quadratic Zeeman shift using stimulated Raman transitions. The quadratic Zeeman shift has been measured yielding Delta nu = 1296.8 +/- 3.3 Hz/G(2) for magnetically insensitive sublevels (5S(1/2), F = 2; m(F) = 0 -> 5S(1/2), F = 3, m(F) = 0) of Rb-85 by compensating the magnetic field and cancelling the ac Stark shift. We also measured the cancellation ratio of the differential ac Stark shift due to the imbalanced Raman beams by using two pairs of Raman beams (sigma(+), sigma(+)) and it is 1:3.67 when the one-photon detuning is 1.5 GHz in the experiment

Fast, high-fidelity, all-optical and dynamically-controlled polarization gate using room-temperature atomic vapor

We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a π phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90° linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2 mW/cm2, which would be equivalent to 0.5 nW of light power (λ = 800 nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.

Cold Atom Interferometry

In this article the recent experimental works on cold atoms carried out at Wuhan Institute of Physics and Mathematics (WIPM) are reported. These include the experimental realization of Bose-Einstein condensation (BEC), different type of cold atom interferometers, and bichromatic electromagnetically-induced transparency (EIT). We have realized BoseEinstein condensates of Rb dilute atomic gases. The apparatus consists of two horizontally mounted magneto-optic-traps (MOTs) and a QUIC magnetic trap. Nearly 3×10 atoms were trapped in the second MOT, and up to 1.2×10 atoms were adiabatically transferred to the QUIC trap. A pure condensate with about 1.1×10 atoms at about 30nK was achieved. We also demonstrated two type of cold atom interferometers, the Sagnac and Ramsey interference fringes were recorded with contrast of up to 37%.

Continuous Dynamic Rotation Measurements Using a Compact Cold Atom Gyroscope

We present an experimental demonstration of the rotation measurement using a compact cold atom gyroscope. Atom interference fringes are observed in the stationary frame and the rotating frame, respectively. The phase shift and contrast of the interference fringe are experimentally investigated. The results show that the contrast of the interference fringe is well held when the platform is rotated, and the phase shift of the interference fringe is linearly proportional to the rotation rate of the platform. The long-term stability, which is evaluated by the overlapped Allan deviation, is 8.5 × 10−6 rad/s over the integrating time of 1000 s.

Extracting the differential phase in dual atom interferometers by modulating magnetic fields

We present a new scheme for measuring the differential phase in dual atom interferometers. The magnetic field is modulated in one interferometer, and the differential phase can be extracted without measuring the amplitude of the magnetic field by combining the ellipse and linear fitting methods. The gravity gradient measurements are discussed based on dual atom interferometers. Numerical simulation shows that the systematic error of the differential phase measurement is largely decreased when the duration of the magnetic field is symmetrically modulated. This combined fitting scheme has a high accuracy for measuring an arbitrary differential phase in dual atom interferometers

Hybrid wide-band, low-phase-noise scheme for Raman lasers in atom interferometry by integrating an acousto-optic modulator and a feedback loop

We report a hybrid scheme for phase-coherent Raman lasers with low phase noise in a wide frequency range. In this scheme, a pair of Raman lasers with a frequency difference of 3.04 GHz is generated by the ±1-order diffracted lights of an acousto-optic modulator (1.52 GHz), where a feedback loop is simultaneously applied for suppressing the phase noise. The beat width of the Raman lasers is narrower than 3 Hz. In the low-frequency range, the phase noise of the Raman lasers is suppressed by 35 dB with the feedback. The phase noise is less than -109  dBc/Hz in the high-frequency range. The sensitivity of an atom gyroscope employing the hybrid Raman lasers can be implicitly improved 10 times. Due to the better high-frequency response, the sensitivity is not limited by the durations of Raman pulses. This work is important for improving the performance of atom-interferometer-based measurements.

Fast, optically controlled Kerr phase shifter for digital signal processing

We demonstrate an optically controlled Kerr phase shifter using a room-temperature 85Rb vapor operating in a Raman gain scheme. Phase shifts from zero to π relative to an unshifted reference wave are observed, and gated operations are demonstrated. We further demonstrate the versatile digital manipulation of encoded signal light with an encoded phase-control light field using an unbalanced Mach-Zehnder interferometer. Generalizations of this scheme should be capable of full manipulation of a digitized signal field at high speed, opening the door to future applications.

Rabi oscillation induced

We present an observation of zero-to-

π

\ensuremath{\pi}

-phase flip in an unbalanced Ramsey atom interferometer

phase flips induced by Rabi oscillation in an unbalanced Ramsey atom interferometer. The phase shift and visibility are experimentally investigated by modulating either the polarization or duration of Raman lasers, and they are well explained by a theoretical model. In an atom interferometer, the