Rapid and robust laser-frequency auto-locking is essential for the field deployment of quantum communications, quantum computing, and precision-measurement technologies; however, achieving this remains a considerable challenge. Here, we propose and demonstrate an auto-locking scheme employing Bayesian optimization and discrete biorthogonal wavelet transformation. First, the reference is rapidly sought by making intelligent use of historical observations, eliminating the inherent blindness of the traditional parameter-scanning method. Second, the frequency reference is robustly identified by pinpointing transition signals with the discrete biorthogonal wavelet transformation and analyzing their immutable frequency differences and relative magnitudes, which are determined by the inherent atomic structure and remain resistant to environmental disturbances. This proposed approach achieves a fivefold acceleration in reference searching compared to conventional scanning methods in the case where the laser frequency drifts far away from the reference. Crucially, it achieves an identification accuracy of more than 99.5

Dynamic atom gravimeters enable absolute gravity measurements on moving platforms. However, their performance is severely degraded due to the complex dynamic environment. This paper finds that the amplitude-modulation noise (AMN) is a key factor contributing to the degradation of gravity- measurement performance. We find that the AMN is induced by the cold atomic cloud trajectory and velocity variation. We build a model to illustrate the principles and magnitude of AMN arising from various experiment processes. Then we propose a method to fit the normalized AMN with respect to the kinematic parameters of the cold atomic cloud and successfully suppress this noise from 0.11 to 0.038 using the fitting result. With this method, we improve the fringe phase resolution from 0.244 to 0.092 rad and reduce the dynamic gravity-measurement noise from 2.69 to 1.68 mGal. This study finds and suppresses a key noise source in dynamic atom gravimeters, which is useful for further improving their precision. The proposed method can also be applied for precision enhancement for other dynamic atom-interferometer-based sensors, such as atom gradiometers and gyroscopes.

We propose and demonstrate a dynamical mirror compensation scheme to restore velocity immunity in a large-area dual-atom-interferometer gyroscope. In an ideal Mach-Zehnder configuration, the phase shift is inherently immune to atomic velocity, but this property is broken by the Earth's rotation via the Coriolis effect. We overcome this by actively rotating the Raman mirrors during the pulse sequence to cancel the time-dependent angular offset. The implementation relies on a decouplable calibration-compensation chain to remove rotation-induced time-dependent terms. The scheme is validated on a dual-atom-interferometer gyroscope with an interference area of 21.1 cm^2. After compensation, the phase's dependence on atomic velocity is reduced 40-fold, and the velocity contribution to scale-factor stability is evaluated to be 0.13 ppm. The sensor achieves a rotation sensitivity of 1.3×10^-8 rad/s/Hz^1/2 and a stability of 1.9×10^-10 rad/s at 4500 s integration, together with a common-mode noise rejection ratio of up to 459, demonstrated in a seismic event. This work removes a key obstacle to scale-factor stabilization in atom-interferometer gyroscopes and paves the way for their applications in inertial navigation and geophysics.

Differential light shift (DLS) is an important error term that limits the atom interferometer’s measurement precision, especially for the case of the electro-optic modulator (EOM)-based scheme, where multiple laser sidebands exist, and their ratios are hard to control synchronously. This article carried out an experimental and theoretical study on this subject. By conducting long-term gravity measurement, we find that the gravity exhibits drifts of about 13.13 μGal, and is strongly correlated to the Raman laser’s sidebands. A model of the DLS-induced gravity error is established and a DLS compensation method is proposed to suppress the gravity drift to 2.54 μGal. Besides the compensation method, we propose a Dual-Sideband Ratio Locking scheme to more robustly eliminate the gravity measurement drift. By feeding back to both the EOM microwave power and the tapered amplifier’s temperature, this method locks both the ±1 order sideband to a stability level of 10−5, which corresponds to a gravity error of less than 0.1 μGal. Long-term gravity measurement is carried out after the locking method, showing a long-term stability of 1.6 μGal. The proposed methods will benefit the suppression of the DLS effect for high-precision atom interference measurement.

We investigate how wave-mixing (WM)-induced symmetry breaking leads to giant third-order polarization rotation of a weak probe field in a Rydberg electromagnetically induced transparency (EIT) medium. A far-detuned counterpropagating WM field is adiabatically eliminated and retained solely as a Raman dressing of the lower Zeeman manifold. In this reduced description, the weak static magnetic field defines the two circular propagation channels, while the WM-induced Raman coherence breaks the symmetry between these channels, without acting as a gain channel or an independent nonlinear source. The weak-probe response is calculated using a reduced density-matrix expansion for van der Waals (vdW) correlations and self-consistent Maxwell-Bloch propagation, with the nonlinear rotation extracted by subtracting the linear propagation background. Including WM dressing increases the extracted third-order rotation from 1.06 degrees to 25.70 degrees, an enhancement of more than 24 times, for the parameters considered. The response is nonmonotonic in WM strength and can even reverse sign, revealing that the WM field controls the propagation channels through symmetry breaking rather than merely amplifying the probe. Eigenchannel diagnostics further indicate that this giant rotation requires coherent excitation of both WM-dressed propagation channels, which in turn depends on three factors: Raman-induced asymmetry, the EIT-supported Rydberg pathway, and vdW nonlocality. These results demonstrate a symmetry-breaking-controlled mechanism for Rydberg magneto-optics, with applications to weak-light polarimetry and all-optical polarization control.

The weak equivalence principle (WEP) is a central pillar of general relativity. Its precise test with quantum systems in space offers a unique window onto new physics. Here, we report an in-orbit quantum test of the WEP. A dual-species (85Rb/87Rb) atom interferometer is realized aboard the China Space Station. Methods of platform motion suppression, fluorescence detection switching, and two-photon detuning switching are developed to eliminate phase noise and improve measurement accuracy. A test uncertainty of 2.8 × 10-8 is obtained from 280 days of WEP test data, and a test result of (-2.7 ± 4.7) × 10-7 is achieved after error estimation. This improves prior atom-interferometric WEP tests in microgravity by three orders of magnitude. This work paves the way for space-borne quantum inertial sensors and their application to future fundamental physics in space.

High-precision gyroscopes in space are essential for fundamental physics research and navigation.Due to its potential high precision,the cold atom gyroscope is expected to be one of the next generation of gyroscopes in space.Here,we report the first realization of a cold atom gyroscope,which was demonstrated by the atom interferometer installed in the China Space Station(CSS) as a payload.By compensating for the CSS's high dynamic rotation rate using a built-in piezoelectric mirror,spatial interference fringes in the interferometer are successfully obtained.Then,the optimized ratio of the Raman laser's angles is derived,the coefficients of the piezoelectric mirror are self-calibrated in orbit,and various systemic effects are corrected.We achieve a rotation measurement resolution of 50 μrad/s for a single shot and 17 μrad/s for an average number of 32.The measured rotation is -1142±29 μrad/s and is compatible with that recorded by the classical gyroscope of the CSS.This study paves the way for developing high-precision cold atom gyroscopes in space.

A dual-atom-interferometer gyroscope has high sensitivity for accurate rotation measurements because of its immunity to common-mode noise. However, a measurement error is induced as the common phase noise, e.g., vibration noise, increases. In this work, we demonstrated a real-time compensation (RTC) scheme to improve the accuracy of measurements of the differential phase in dual atom interferometers. The vibration noise was measured by two seismometers and its induced phase shift was fed back to the Raman lasers after this shift was calculated based on the sensitivity function of the atom interferometers. After the RTC module was applied, the interference signals obtained via the square modulation method were stabilized at their midfringe points, which caused the vibration-induced phase noise for each of the atom interferometers to decrease from 495 mrad to 165 mrad. The differential phase error obtained by the dual atom interferometers and two seismometers was reduced from 114.8 mrad to 49.6 mrad, which implies that the rotation measurement error was improved by a factor of 2.3. This work paves the way to accurately measuring the rotation signal and has promising applications in fields of precision measurements.

Inertial navigation systems (INSs) exhibit distinctive characteristics, such as long-duration operation, full autonomy, and exceptional covertness compared to other navigation systems. However, errors are accumulated over time due to operational principles and the limitations of sensors. To address this problem, this study theoretically explores a numerically simulated integrated inertial navigation system consisting of a single-axis cold atom interferometer gyroscope (CAIG) and a conventional inertial measurement unit (IMU). The system leverages the low bias and drift of the CAIG and the high sampling rate of the conventional IMU to obtain more accurate navigation information. Furthermore, an adaptive gradient ascent (AGA) method is proposed to estimate the variance of the measurement noise online for the Kalman filter. It was found that errors of latitude, longitude, and positioning are reduced by 43.9%, 32.6%, and 32.3% compared with the conventional IMU over 24 h. On this basis, errors from inertial sensor drift could be further reduced by the online Kalman filter.

Operating atom-interferometer gyroscopes outside a laboratory environment is challenging primarily owing to the instability of laser systems. To enhance the thermal stability of free-space laser systems, a compact laser system using fiber lasers and all-quartz-jointed optical modules was developed for a dual-atom-interferometer gyroscope. Millimeter-scale optical elements jointed on quartz plates with identical quartz supports, ensure laser power stability and facilitate component upgrades. The primary diode laser was locked to the modulation transfer spectrum of Rb atoms, and Raman lasers were phase-locked to the primary laser. Frequencies for repumping, blow-away, and detection lasers were adjusted with acousto-optic modulators. At room temperature, laser power fluctuation was under 1:1000, polarization extinction ratio exceeded 30 dB, frequency fluctuation was below 91 kHz, and phase noise reached to -100 dBc/Hz @ 1 kHz. The optical modules were tested at 5-50 degrees C and applied to a dual-atom-interferometer gyroscope. The fringe contrast was tested over the temperature range. The proposed system paves the way for promoting field applications of atom-interferometer sensors.

Atom interferometry shows high sensitivity for inertial measurements in the laboratory, but it faces difficulties in field applications because of a trade-off between sensitivity and size. Therefore, there is an urgent need to develop a small sensor with high resolution for measuring acceleration and rotation in inertial navigation applications. Presented here is a miniaturized inertial sensor capable of measuring acceleration and rotation simultaneously based on high-resolution dual atom interferometers. A sensor head is integrated within a volume of 100 l, in which the vacuum chambers are fabricated by bonding quartz-glass windows with epoxy resin. A photoelectric cabinet is composed of four 3U rack units by integrating optical modules and electronic units. Dual atom interference fringes with a contrast of 29% are observed, and the acceleration and rotation are measured simultaneously by extracting their phase shifts. By developing a temperature compensation method to eliminate phase drifts caused by the thermal deformation of the Raman mirrors and using wave vector reversal to eliminate the phase drifts independent of the direction of the wave vector, measurement resolutions of 40 ng at 518 s and 6.1 nrad/s at 10 880 s are achieved for acceleration and rotation, respectively, from Allan deviations.

Atom interferometers based on the matter wave interferometry are promising tools for precision measurements. In laboratory, they have been used in the field of fundamental physics research. An important research effort is going on to miniaturize them, which can help to make them play a key role in resource exploration, inertial navigation and gravity mapping from space. The miniaturization of a laser system is a key link to miniaturize an atom interferometer. However, because the atoms used for the frequency stabilization in the existing schemes of the Raman laser system and the atoms used as the test masses in the atom interferometers are of the same type, the special optical elements and their driving devices are used to obtain the far detuning of the Raman lasers by frequency offset locking method, which makes the laser system complex and affects its reliability. Meanwhile, the increase in weight and cost of the laser system is adverse to apply them in the field of inertial navigation and space application. For an atom interferometer using one type of Rb isotope atoms as test mass, a frequency-stabilized Raman laser system based on another type of Rb isotope atoms saturated absorption spectrum is proposed to make the laser system for an atom interferometer compact and robust.This Raman laser system is helpful to miniaturize the laser systems of atom interferometers, and promotes the atom interferometers to be applied in movable platforms or in the weight-sensitive fields. For an Rb-85 atom interferometer, the frequency-stabilized Raman laser system based on Rb-87 atom saturated absorption spectrum is proposed to make the laser system compact and robust. First, the schematic of the stabilizing frequency and detuning of Raman laser is introduced. Second, the frequency-stabilized Raman laser system based on Rb-87 atom saturated absorption spectrum is proposed. In this Raman laser system, the frequency of the Raman laser is stabilized to the Rb-87 atom saturated spectrum to obtain the far detuning. Then, the laser beam from the Raman laser is modulated by an electro-optic modulator with driving frequency of 3.04 GHz. Amplified by a tapered amplifier, the carrier and +1st bandside in modulated laser beams are used as the Raman beams. The frequency stabilization experiment is done. By scanning the injection current and the voltage of the piezoelectric transducer of the Raman laser, the Rb saturated absorption spectrums are obtained. The frequency of the Raman laser is stabilized to the peak of Rb-87 atomF = 2 -> F '= CO2, 3transition of D-2 line, obtaining a red detuning of a magnitude of GHz and a linewidth of 80 kHz. The Raman beams generated by this Raman laser system are used to one atom interferometer of the atom gradiometer to evaluate its performance. The sensitivity of the atom interferometer using this Raman beams is 345 mu Gal/Hz(1/2) with the interference fringe contrast of 20%. And the Allan deviation of the gravity measurement more than one day shows that the resolution of the atom interferometer is 2x10(-8) g@7 500 s. It is calculated that the noise of the gravity measurement per shot contributed by the frequency noise of the Raman laser beams is less than 1 mu Gal. This Raman laser system uses an electro-optic modulator to generate a Raman beams, which inherits the advantages of the existing Raman schemes based on an electro-optic modulator. In this Raman laser system, a Rb cell is used as a substitute for an acousto-optic or electro-optic modulator to stabilize the frequency of the Raman laser and obtain the far detuning, which not only simplifies the light path and electric circuit of the Raman laser system, but also improves the reliability and long-term stability of the Raman beams. Both the atom interference experiment in the atom interferometer and the theoretical evaluation show that this Raman laser system is able to meet the miniaturized atom interferometers applied requirements. This Raman laser system is helpful to realize the miniaturization and weight reduction of the laser systems and promotes the atom interferometers to be applied in the movable platforms and in space.

Large momentum transfer (LMT) is a crucial technique for achieving high-precision atom interferometer inertial sensors. However, the transfer efficiency of multi-pulse sequences is limited by optical power variations, Doppler detunings, and other systematic effects in a Mach-Zehnder interferometer. In this study, we investigated the robustness of LMT atom interferometry using Raman adiabatic rapid passage (RARP). The results showed that the RARP pulses exhibited a high transfer efficiency and good robustness, and they were applied to the construction of an LMT atom interferometer with a momentum transfer up to 14 (h) over bark. In the case of 6 (h) over bark, the phase offset of the atom interferometer with RARP multi-pulse sequences had an 8.4-fold advantage in robustness over that with Raman multi-pulse sequences. These findings provide an efficient and practical approach for developing compact mobile inertial sensors with improved contrast and higher accuracy in dynamic environments.

Atom-interferometer gyroscopes have attracted much attention for their long-term stability and extremely low drift. For such high-precision instruments, self-calibration to achieve an absolute rotation measurement is critical. In this work, we propose and demonstrate the self-calibration of an atom-interferometer gyroscope. This calibration is realized by using the detuning of the laser frequency to control the atomic velocity, thus modulating the scale factor of the gyroscope. The modulation determines the order and the initial phase of the interference stripe, thus eliminating the ambiguity caused by the periodicity of the interferometric signal. This self-calibration method is validated through a measurement of the Earth's rotation rate, and a relative uncertainty of 162 ppm is achieved. Long-term stable and self-calibrated atom-interferometer gyroscopes have important applications in the fields of fundamental physics, geophysics, and long-time navigation.

In spin-exchange-relaxation-free (SERF) atomic magnetometers (AMs), the attenuation of circularly polarized pump beam introduces spatial-dependent artificial magnetic fields in atomic spin polarization and light shift. In general, such a spatial-dependent effective magnetic field, especially prevalent in single-cell magnetometer arrays, cannot be uniformly compensated over the entire excitation region, resulting in a complex distributed compensation mask effect. In addition, any external effective-field-compensation methods inevitably complicate the final analysis of the unknown magnetic field measured. Here, we report a new excitation scheme that can substantially suppress spatial nonuniformity due to pump beam attenuation. Using counter-propagating pump beams with symmetrically red- and blue-detuning-paired frequencies, we demonstrate a significant reduction of spatial inhomogeneity in atomic spin polarization and light shift in comparison with the usual single-frequency unidirection and counter-propagating pump schemes. Employing this red-/blue-detuning-paired pump scheme, we construct a single-cell, four-channel SERF magnetometer array with high spatial homogeneity. We demonstrate similar to 10-fT/Hz(1/2) sensitivity in the 5-45-Hz band for all four channels, with a gradient sensitivity of 2 fT/Hz(1/2) cm in the same band. This new scheme enables the development of single-vapor-cell, high-uniformity multichannel magnetic field mapping devices with potential applications in magnetoencephalography (MEG) and magnetocardiography (MCG), or in searching for exotic spin-dependent interactions.

A dynamic gravimeter with an atomic interferometer (AI) can perform absolute gravity measurements with high precision. AI-based dynamic gravity measurement is a type of joint measurement that uses an AI sensor and a classical accelerometer. The coupling of the two sensors may degrade the measurement precision. In this study, we analyzed the cross-coupling effect and introduced a recovery vector to suppress this effect. We improved the phase noise of the interference fringe by a factor of 1.9 by performing marine gravity measurements using an AI-based gravimeter and optimizing the recovery vector. Marine gravity measurements were performed, and high gravity measurement precision was achieved. The external and inner coincidence accuracies of the gravity measurement were ±0.42 mGal and ±0.46 mGal after optimizing the cross-coupling effect, which was improved by factors of 4.18 and 4.21 compared to the cases without optimization.

Herein, we propose a scheme for developing a large -momentum -transfer atom interferometer based on the top -hat composite light pulse technique. Additionally, we analyze the contrast and phase noise using a theoretical model of the sensitivity function of the proposed atom interferometer. A top -hat composite light pulse is used to simulate calculations based on the atom interferometer. We confirm that compared with a Gaussian beam, a top -hat composite light pulse can improve the consistency of atom cloud transitions and increase the contrast of atom interference fringes. By designing symmetrical and reversed composite pulse sequences, the phase noise and vibration noise in the time interval and free evolution process of multipulse action can be suppressed. The numerical simulation results show that the sensitivity of the proposed atom interferometer using a top -hat composite light pulse increases by one order of magnitude compared with that using a Gaussian beam. Moreover, the proposed atom interferometer achieves satisfactory suppression of external technical noise.

Cold-atom interferometers have matured into a powerful tool for fundamental physics research, and they are currently moving from realizations in the laboratory to applications in the field. A radio frequency (RF) generator is an indispensable component of these devices for controlling lasers and manipulating atoms. In this work, we developed a compact RF generator for fast switching and sweeping the frequencies and amplitudes of atomic-interference pulse sequences. In this generator, multi-channel RF signals are generated using a field-programmable gate array (FPGA) to control eight direct digital synthesizers (DDSs). We further propose and demonstrate a method for pre-loading the parameters of all the RF pulse sequences to the DDS registers before their execution, which eliminates the need for data transfer between the FPGA and DDSs to change RF signals. This sharply decreases the frequency-switching time when the pulse sequences are running. Performance characterization showed that the generated RF signals achieve a 100 ns frequency-switching time and a 40 dB harmonic-rejection ratio. The generated RF pulse sequences were applied to a cold-atom-interferometer gyroscope, and the contrast of atomic interference fringes was found to reach 38%. This compact multi-channel generator with fast frequency/amplitude switching and/or sweeping capability will be beneficial for applications in field-portable atom interferometers.

Neutral atom platform has become an attractive choice to study the science of quantum information and quantum simulation, where intense efforts have been devoted to the entangling processes between individual atoms. For the development of this area, two-qubit controlled-PHASE gate via Rydberg blockade is one of the most essential elements. Recent theoretical studies have suggested the advantages of introducing non-trivial waveform modulation into the gate protocol, which is anticipated to improve its performance towards the next stage. We report our recent experimental results in realizing a two-qubit controlled-PHASE($C_Z$) gate via off-resonant modulated driving(ORMD) embedded in two-photon transition for Rb atoms. It relies upon a single modulated driving pulse with a carefully calculated smooth waveform to gain the appropriate phase accumulations required by the two-qubit gate. Combining this $C_Z$ gate with global microwave pulses, two-atom entanglement is generated with the raw fidelity of 0.945(6). Accounting for state preparation and measurement (SPAM) errors, we extract the entanglement operation fidelity to be 0.980(7). Our work features completing the $C_Z$ gate operation within a single pulse to avoid shelved Rydberg population, thus demonstrate another promising route for realizing high-fidelity two-qubit gate for neutral atom platform.

由于原子干涉陀螺仪具有灵敏度高和长期稳定性好等特点,在惯性导航、精密测量、测地学等领域有着重要的应用前景,因此,研制高精度原子干涉陀螺仪具有重要的科学意义和应用价值,已成为当今研究的热点课题之一.首先综述了国内外原子干涉陀螺仪的研究进展和发展趋势.然后分析了广义相对论检验和惯性导航应用对原子干涉陀螺仪的需求,介绍了10余年来在原子干涉仪、萨格纳克效应和原子干涉陀螺仪方面取得的研究成果.最后讨论了原子干涉陀螺仪的优缺点,并展望了原子干涉陀螺仪的发展机遇及其在精密测量和惯性导航领域面临的挑战.