Optical tomography can reveal the intrinsic structure of complex objects with high accuracy. Cold atoms are an excellent model physical system for designing new protocols. By combining the gradient echo memory protocol with spatial homodyne detection, our experiment achieved micron-level resolution and excellent shot-noise limited sensitivity for interrogating atomic coherence. We also demonstrated three-dimensional imaging of an external magnetic field, and plan to extend the scheme to ultra-sensitive three-dimensional imaging of microwave fields using Rydberg atoms. Our work pushes the boundaries of quantum sensing for weak fields and unexplored three-dimensional tomographic imaging. The method may also be applied to hot atoms or solid-state probes, such as color centers, or ions, embedded in an interrogated medium.
Optical tomography can reveal the intrinsic structure of complex objects with high accuracy. Cold atoms are an excellent model physical system for designing new protocols. By combining the gradient echo memory protocol with spatial homodyne detection, our experiment achieved micron-level resolution and excellent shot-noise limited sensitivity for interrogating atomic coherence. We also demonstrated three-dimensional imaging of an external magnetic field, and plan to extend the scheme to ultra-sensitive three-dimensional imaging of microwave fields using Rydberg atoms. Our work pushes the boundaries of quantum sensing for weak fields and unexplored three-dimensional tomographic imaging. The method may also be applied to hot atoms or solid-state probes, such as color centers, or ions, embedded in an interrogated medium.
Abstract Magnetic resonance imaging is a three-dimensional imaging technique, where a gradient of the magnetic field is used to interrogate spin resonances with spatial resolution. The application of this technique to probe the coherence of atoms with good three-dimensional resolution is a challenging application. We propose and demonstrate an optical method to probe spin resonances via a two-photon Raman transition, reconstructing the 3D-structure of an atomic ensemble’s coherence, which is itself subject to external fields. Our method relies on a single time-and-space resolved heterodyne measurement, allowing the reconstruction of a complex 3D coherence profile. Owing to the optical interface, we reach a tomographic image resolution of 14 × 14 × 36 μm3. The technique allows to probe any transparent medium with a resonance structure and provides a robust diagnostic tool for atom-based quantum information protocols. As such, it is a viable technique for application to magnetometry, electrometry, and imaging of electromagnetic fields.
In this work we describe the design and implementation of an optical system that enables the study of the interactions of Rydberg atoms or other Rydberg species in well-defined geometries. To understand and observe the dynamics of Rydberg interactions, the ability to engineer different arrangements of microscopic cold atom traps and manipulate their positions with a precision of a few microns is essential. This is accomplished by a custom designed high-numerical-aperture long-working-distance objective lens and a spatial light modulator device to control the phase of an incoming optical beam. Several different trap geometries have been realized, with a spatial resolution of a few microns, including a 1-dimensional chain, a 2-dimensional square grid, and a circular array of traps. The objective lens has been designed to provide diffraction limited performance at multiple wavelengths facilitating the creation of not only micron-scale atom traps but also the fluorescence imaging of trapped atoms. The system enables precise control over trap positions, and hence the locations at which atoms might be excited, with applications in, for example, the study of long-range interactions between Rydberg atoms, the creation of long-range Rydberg molecules, the implementation of qubits for quantum computing based on Rydberg atoms, and in quantum simulation.
With the continuous advancement and maturation of laser cooling techniques for atoms and molecules and full-dimensional electron and ion imaging technology, using momentum imaging techniques to investigate the characteristic properties of cold atoms and collision dynamics has emerged as a burgeoning research direction. This progress has driven the development of a series of high-resolution electron and ion detection devices, leading to innovative breakthroughs in fields such as cold molecule reactions, Rydberg atoms, nuclear decay, photoionization of Bose-Einstein condensates (BECs) and cold plasmas, collisions between cold atoms and ions/electrons, coherent control of cold atoms, and strong-field ultrafast physics. This article reviews representative instruments and their corresponding seminal achievements in the following domains: In cold molecular/cold chemical reactions, imaging technology has revealed new insights into reaction mechanisms; For cold Rydberg atom interactions, it demonstrates high-precision quantum state manipulation capabilities, advancing quantum information processing; In nuclear decay research, it provides ultra-sensitive detection methods, deepening understanding of decay processes; For BEC photoionization and cold plasma control, it can precisely monitor and manipulate microscopic processes; In cold atomic collision studies, it reveals new details in collision dynamics, refining collision theories; Regarding coherent control of cold atoms, it achieves accurate quantum state manipulation and interference; In strong-field ultrafast processes, it elucidates complex electron dynamics under intense fields, providing innovative methods for ultrafast laser control. Furthermore, this article summarizes the applications of imaging technologies in the aforementioned research areas involving cold atoms, and provides prospects for future developments in this evolving field.
Cold atoms are a quantum system well-isolated from the environment. Since the 80s, they have been used to make high-sensitivity atomic sensors and to deepen the understanding of quantum physics phenomena. At low temperatures, degenerate atomic gas regimes can be reached. They are characterized by a macroscopic quantum state that can be manipulated and controlled by lasers. Placing such atomic wave function in optical lattices provide a way to study the dynamics of complex many-body systems. In this context, diffraction-limited quantum gas microscopes have emerged as standard tools to probe such complex systems and to measure atomic density correlations between lattice sites. By further reducing the optical lattices dimensions, the energy scales are strongly enhanced and favor novel quantum phases. Such reduction of optical lattice dimensions requires novel trapping and imaging techniques to manipulate cold-atoms with subwavelength spatial resolutions.In this PhD thesis, we experimentally perform subwavelength imaging of ultra-cold atoms of Rubidium 87 using a dressed excited state method, initially proposed for generating subwavelength trapping potentials. The measurement are performed using in situ absorption imaging. A quantitative comparison of data and theory lead us to reinterprete and modify a method for atom number calibrations that is commonly used in the community. This reinterpretation requires a fine understanding of the interaction of a single quantum multi-level system and a coherent saturating field. The measurement of the in situ transmission of a coherent probe shows a linear reduction of the single-atom scattering cross-section with the optical density for which we propose a physical interpretation and a model. Once calibrated, we use our subwavelength imaging method that reaches down to 20 nm resolution in a few microseconds to super-resolve a tiny quantum object : the longitudinal wave function of a BEC in a very tight lattice.
Rydberg atom-based sensors have emerged as highly sensitive tools for terahertz (THz) metrology, yet most current imaging techniques discard crucial phase information. In this Letter, we present a coherent THz-to-optical conversion scheme in warm Rb vapor that enables complex-amplitude field imaging. By manipulating the phase-matching conditions via an adjustable interference pattern of optical probe beams, we demonstrate the ability to perform tomographic reconstruction of the THz field distribution. We experimentally validate the spatial resolution and phase-sensitivity of the system by resolving sub-centimeter features and identifying incident angles of arrival. Our results establish a robust framework for phase-resolved THz imaging and holography using atomic vapors at room temperature.
We report on an ion-optical system that serves as a microscope for ultracold ground state and Rydberg atoms. The system is designed to achieve a magnification of up to 1000 and a spatial resolution in the 100 nm range, thereby surpassing many standard imaging techniques for cold atoms. The microscope consists of four electrostatic lenses and a microchannel plate in conjunction with a delay line detector in order to achieve single particle sensitivity with high temporal and spatial resolution. We describe the design process of the microscope including ion-optical simulations of the imaging system and characterize aberrations and the resolution limit. Furthermore, we present the experimental realization of the microscope in a cold atom setup and investigate its performance by patterned ionization with a structure size down to 2.7 μ m. The microscope meets the requirements for studying various many-body effects, ranging from correlations in cold quantum gases up to Rydberg molecule formation.