Strong laser fields and their power to generate controllable high-photon-number coherent-state superpositions
Javier Rivera-Dean, Theocharis Lamprou, Emilio Pisanty, Philipp Stammer, Andrés Felipe Ordóñez-Lasso, Andrew Maxwell, Marcelo F. Ciappina, Maciej Lewenstein, P. Tzallas
In an effort to better bridge quantum optics and strong-field physics, the authors demonstrate the ability of intense laser-atom interactions to generate coherent-state superpositions and tune their quantum properties. They show that these superpositions can transition from optical ``cat'' states to ``kitten'' states with a change in atomic density, and report the highest-photon-number optical cat state to date.
In an effort to better bridge quantum optics and strong-field physics, the authors demonstrate the ability of intense laser-atom interactions to generate coherent-state superpositions and tune their quantum properties. They show that these superpositions can transition from optical cat'' states to kitten'' states with a change in atomic density, and report the highest-photon-number optical cat state to date.
Recently we have demonstrated the quantum nature of light in strongly laser driven atoms, and we have shown how the process of high harmonic generation can be used for the creation of highly non-classical light states, in particular superpositions of two coherent states, i.e., optical Schr\{o}dinger states [M. Lewenstein et al., Generation of optical Schr\odinger cat states in intense laser-matter interactions, Nat. Phys., 17 1104-1108 (2021)]. Here, we investigate the quantum optical description of the interaction, incorporating many atoms and the back-action of the high harmonic generation or above threshold ionization processes on the coherent state of the driving laser field. We show how the conditioning on high harmonic generation and above threshold ionization can lead to non-classical light states, and we discuss the key parameters that can be used for controlling and characterizing the non-classical states obtained after high harmonic generation. The theoretical results have been experimentally confirmed by demonstrating how the obtained coherent state superposition changes from an optical to kitten state by changing the number of atoms participating in the high harmonic generation process. Additionally, we experimentally verify the applicability of the approach for generating high photon number non-classical light states. This is shown by demonstrating the generation of a 9--photon optical state which, to our knowledge, is the highest photon number optical state experimentally reported. Our findings anticipate the development of new methods that naturally lead to the creation of high photon number controllable coherent state superpositions, advancing investigations in quantum technology.
Recently, using conditioning approaches on the high-harmonic generation process induced by intense laser-atom interactions, we have developed a new method for the generation of optical Schrödinger cat states (Lewenstein et al. in Nat Phys, 17 1104–1108, 2021. https://doi/10.1038/s41567-021-01317-w). These quantum optical states have been proven to be very manageable as, by modifying the conditions under which harmonics are generated, one can interplay between kitten and genuine cat states. Here, we demonstrate that this method can also be used for the development of new schemes towards the creation of optical Schrödinger cat states, consisting of the superposition of three distinct coherent states. Apart from the interest these kind of states have on their own, we additionally propose a scheme for using them towards the generation of large cat states involving the sum of two different coherent states. The quantum properties of the obtained superpositions aim to significantly increase the applicability of optical Schrödinger cat states for quantum technology and quantum information processing.
We present a theoretical demonstration on the generation of entangled coherent states and of coherent state superpositions, with photon numbers and frequencies orders of magnitude higher than those provided by the current technology. This is achieved by utilizing a quantum mechanical multimode description of the single- and two-color intense laser field driven process of high harmonic generation in atoms. It is found that all field modes involved in the high harmonic generation process are entangled, and upon performing a quantum operation, lead to the generation of high photon number optical cat states spanning from the far infrared to the extreme ultraviolet spectral region. This provides direct insights into the quantum mechanical properties of the optical field in the intense laser matter interaction. Finally, these states can be considered as a new resource for fundamental tests of quantum theory, quantum information processing, or sensing with nonclassical states of light.
Intense laser-matter interactions are at the center of interest in research and technology since the development of high-power lasers.They have been widely used for fundamental studies in atomic, molecular, and optical physics, and they are at the core of attosecond physics and ultrafast optoelectronics.Although the majority of these studies have been successfully described using classical electromagnetic fields, recent investigations based on fully quantized approaches have shown that intense laser-atom interactions can be used for the generation of controllable high-photon-number entangled coherent states and coherent state superpositions.In this tutorial, we provide a comprehensive fully quantized description of intense laseratom interactions.We elaborate on the processes of high-harmonic generation, above-threshold ionization, and we discuss new phenomena that cannot be revealed within the context of semiclassical theories.We provide the description for conditioning the light field on different electronic processes, and their consequences for quantum state engineering of light.Finally, we discuss the extension of the approach to more complex materials, and the impact to quantum technologies for a new photonic platform composed of the symbiosis of attosecond physics and quantum information science.
High-harmonic generation is one of the most fundamental processes in strong laser-field physics that has led to countless achievements in atomic physics and beyond. However, a rigorous quantum electrodynamical picture of the process has never been reported. Here, we prove rigorously and demonstrate experimentally that the quantum state of the driving laser field, as well as that of harmonics, is coherent. Projecting this state on its part corresponding to harmonic generation, it becomes a superposition of a state, amplitude-shifted due to the quantum nature of light, and the initial state of the laser. This superposition interpolates between a Schrodinger kitten, and a genuine Schrodinger cat state. This work opens new paths for ground-breaking investigations in strong laser-field physics and quantum technology. We dedicate the work to the memory of Roy J. Glauber, the inventor of coherent states.
We discuss several methods to produce superpositions of optical coherent states (also known as “cat states”). Cat states have remarkable properties that could allow them to be powerful tools for quantum information processing and metrology. A number of proposals for how one can produce cat states have appeared in the literature in recent years. We describe these proposals and present a new simulation and analysis of them incorporating practical issues such as photon loss, detector inefficiency, and limited strength of nonlinear interactions. We also examine how each would perform in a realistic experiment.