We demonstrate an atom interferometer gyroscope (AIG) using a strontium thermal beam. Our compact AIG consists of a stream of strontium atoms interacting with three laser pulses that split and recombine the matterwave flux to create a Mach-Zhender (MZ) interferometer sensitive to rotation. This system requires no cooling, no state preparation, and requires no microwave components. We also demonstrate a novel phase modulation technique for detecting the AIG response, which is especially useful for interferometers with a short time-of-flight. We will discuss our approach, latest results, and future plans. This thesis is organized in the following manner: Chapter 1 provides context to this work followed by relevant properties of ⁸⁸Sr. An overview of atom interferometry gyroscopes is covered in Chapter 2 followed by an explanation of phase modulation and its use in signal extraction in Chapter 3. Chapter 4 covers numerical investigation of the system parameter space. Next, the experimental apparatus is discussed in Chapter 5 followed by the results of our efforts in Chapter 6. Finally, Chapter 7 provides a summary of the most notable conclusions in this work.
We demonstrate an atom interferometer gyroscope (AIG) using a strontium thermal beam. Our compact AIG consists of a stream of strontium atoms interacting with three laser pulses that split and recombine the matterwave flux to create a Mach-Zhender (MZ) interferometer sensitive to rotation. This system requires no cooling, no state preparation, and requires no microwave components. We also demonstrate a novel phase modulation technique for detecting the AIG response, which is especially useful for interferometers with a short time-of-flight. We will discuss our approach, latest results, and future plans. This thesis is organized in the following manner: Chapter 1 provides context to this work followed by relevant properties of ⁸⁸Sr. An overview of atom interferometry gyroscopes is covered in Chapter 2 followed by an explanation of phase modulation and its use in signal extraction in Chapter 3. Chapter 4 covers numerical investigation of the system parameter space. Next, the experimental apparatus is discussed in Chapter 5 followed by the results of our efforts in Chapter 6. Finally, Chapter 7 provides a summary of the most notable conclusions in this work.
We demonstrate a strontium thermal beam atom interferometer gyroscope (AIG) on a rotation table using the 1S0-$ ^{3\!}P_1$ intercombination line, and measure large rotation rates exceeding 6 rad/s. Our demonstration relies upon a transit-time-resonant (TTR), phase modulation technique for detecting the AIG phase which rejects signal background and variations in fringe amplitude.
Atom interferometry is a formidable tool to explore both fundamental and applied physics. While earlier research mainly concentrated on alkali atoms, there has been a rising interest in leveraging the clock transition of alkaline-earth-like atoms, specifically strontium. Consequently, a few atom interferometers utilizing strontium have been established worldwide in the last years.The primary focus of this work is twofold: firstly, to develop a compact and high-flux source of cold 88Sr atoms utilizing a novel Zeeman slower, a technique that efficiently decelerates the atomic thermal beam produced by an oven using lasers and magnetic fields. Secondly, the study explores the foundational aspects of an atom interferometer based on 88Sr.
As an important technique for developing high-precision gyroscopes, atom interferometry with continuous atomic beams has exhibited advantages of high short-term sensitivity and dynamic response relative to that with periodically launched atom clouds. This article reanalyzes the characteristics of an atomic beam interferometric gyroscope from perspectives including the continuous operation mode and the modified sensitivity dependence on laser and atomic sources. Specific requirements on certain experimental parameters are explored including the Raman beam diameter, detection beam diameter, atomic flux, laser power, laser phase noise, atomic longitudinal and transverse velocity distributions. The parameter determining strategy is discussed to achieve target sensitivity with controlled conditions such as system volume and operating bandwidth. The results would provide strong support on analytical method and data reference for further improvement of atomic beam interferometric gyroscopes.
The utilization of light-pulse atom interferometry presents a valuable technique that has found application in both fundamental scientific inquiries, such as investigating constants such as measurements of fine structure constant α and gravitational constant G, and practical endeavors including acceleration sensing and rotation measurements. This thesis delves into our implementation of a dual atom interferometer design involving the clock transition 1S0 → 3P0 in strontium, concurrently conducting the interferometric sequence on atoms in both ground and excited states. To facilitate the dual atom interferometer’s operation, we have firstly established a compact experimental setup with a transversely loaded bi-dimensional magneto-optical-trap (2D-MOT) to create a high flux source of cold strontium atoms. Introducing a novel cross-polarized bi-color atomic beam slower, we simultaneously addresses two excited Zeeman substates of the transition 1S0 → 1P1 in strontium-88, significantly enhancing the number of atoms prepared in the 461 nm MOT by around 10-fold. Following the 461 nm MOT, the atomic ensemble undergoes cooling in a 689 nm MOT, achieving atomic temperatures below 1 µK. We also install a network of eight magnetic field probes arranged around the cold atomic sample, enabling precise three-axis active control of magnetic fields down to the milligauss level. With the atoms confined in a 2D lattice at the magic-wavelength of 813.427 nm after the initial preparation phase, we conduct the magnetically-induced clock transition to create a statistical mixture state of ground and excited states. After a velocity selection stage, implementing a Mach-Zehnder interferometer with Bragg pulses operating at the magic-wavelength along the vertical axis, we conduct tests of the weak equivalence principle (WEP). The Eötvös ratio we found in our system stood at (1.8 ± 3.1) × 10−4, mainly limited by the finite temperature of the atomic cloud constraining the interrogation time. Furthermore, the dual atom interferometer scheme enables the measurement of state-dependent force and eventually polarizability difference via the phase shift between the atoms in different states, and we experimentally demonstrate this by introducing an additional light field gradient.
A rotation-rate sensor was developed using atom interferometry and the Sagnac effect for matter waves. This device has a short-term sensitivity of 6× 10−10 rad/sec for a 1 second integration time, which is the best publicly reported value to date. It has high intrinsic accuracy because it relies on interactions between atoms and laser light that is stabilized to an atomic transition. Long-term stability is promising and characterization is currently underway. Potential applications include inertial navigation, geophysical studies, and general relativity tests such as verification of the Lense-Thirring and geodetic effects. The principle of operation is as follows: A thermal cesium atomic beam crosses three laser interaction regions where two-photon stimulated Raman transitions between cesium ground states transfer momentum to atoms and divide, deflect, and recombine the atomic wavepackets. Rotation induces a phase shift between the two possible trajectories and causes a change in the detected number of atoms with a particular internal state. Counterpropagating atomic beams form two interferometers using shared lasers for common-mode rejection, and the rotation phase shifts have opposite sign since the phase shift is proportional to the vector velocity of the atoms. Therefore, subtracting or adding the interferometer signals discriminates between rotation and transverse acceleration summed with laser arbitrary phase. Furthermore, in the inertial reference frame of the atoms, rotations Doppler-shift the Raman lasers. Adding Raman frequency shifts to cancel these Doppler-shifts allows operation at an effective zero rotation rate, improving sensitivity and bandwidth. Modulating these frequency shifts facilitates sensitive lock-in detection readout techniques.
Developments in the precise control of quantum systems have led to advances in both fundamental research and emerging technologies in areas including quantum sensing and computation. One particularly useful application is atom interferometry, which uses laser pulses to split, redirect, and recombine atomic wavepackets, enabling precision measurements of inertial effects. This thesis presents the construction and characterisation of a compact cold atom interferometer, to meet the longer-term aim of developing an atomic gyroscope. We detail the setup of a rubidium-85 Magneto-Optical Trap (MOT) and the development of a laser to perform Raman transitions across the hyperfine Rb-85 levels. We then demonstrate and characterise the coherent manipulation of the atomic state of the rubidium as well as atom-interferometric fringes, in a Doppler-insensitive configuration. Systematic errors can degrade the performance of laser pulse interactions with cold atoms by reducing the fidelity of the atom–light interactions. In this thesis, we investigate the implementation of composite pulses and optimal control pulses, which use pulses with varying phase sequences and durations to mitigate against experimental inhomogeneities. We also show that phase modulators can introduce distortions in both the applied laser phase and the Raman modulation amplitude, which can in turn degrade pulse performance. To address this, we develop a compensation protocol that corrects for these non-linearities and demonstrate that it leads to a further improvement in pulse fidelity, for the Waltz and Knill composite pulses. Applying this protocol to the rotary echo sequence led to Rabi oscillations that could last 4 times longer, compared to the uncalibrated IQ modulator. Although an optimal control inversion pulse showed more resilience to the IQ modulator distortions, the Mach-Zehnder interferometer sequence was more susceptible to them. It was demonstrated that compensating for IQ modulator non-linearities improved the optimised fringe signal-to-noise ratio, and reduced the phase-offset error by a factor of 2.4.