Single-Photon Cycle Transfers Molecules into Optical Trap with Up to 4% Efficiency

Controlling the motion of individual molecules represents a significant challenge in modern physics, with implications for understanding fundamental interactions and developing new technologies, and researchers are now demonstrating a novel approach to achieving this. Bart Schellenberg, Eifion Prinsen, and colleagues at the University of Groningen, along with Janko Nauta from CERN, present a method for capturing molecules within an optical trap using only a single photon’s absorption and emission. This technique successfully transfers molecules from a slow beam into the trap by exploiting state-dependent potentials created with an electric field, and crucially, it avoids the need for repeatedly cycling laser cooling, thereby expanding the range of molecules suitable for research. The team estimates an initial efficiency of around 0. 04%, potentially capturing up to 103 molecules per attempt, with prospects for a twenty-fold improvement through field modulation, and this irreversible loading process allows for the accumulation of larger molecular samples over time, opening new avenues for precision measurements and investigations into cold molecular systems

Researchers propose a scheme to transfer molecules from a slow beam into an optical trap using a single photon’s absorption and emission. The efficiency of this scheme receives numerical exploration for barium fluoride, utilising realistic experimental parameters. The technique exploits a state-dependent potential created by an external electric field to trap molecules initially travelling at approximately 10 meters per second. A rapid optical transition transfers them into a roughly seven millikelvin optical dipole trap, and the team estimates the per-shot efficiency for a pulsed, decelerated molecular beam.

Barium Fluoride Preparation for EDM Searches

This is a comprehensive study of laser cooling and trapping barium fluoride (BaF) molecules, focused on preparing for a search for the electron electric dipole moment (EDM). Detecting a non-zero electric dipole moment would violate a fundamental symmetry of particle physics and potentially explain the observed imbalance between matter and antimatter. BaF is an excellent candidate molecule for these searches due to its relatively simple structure and the potential for achieving high precision measurements. The research involves extensive theoretical calculations, using methods like Coupled Cluster and Dirac-Hartree-Fock, to determine the energy levels and properties of BaF.

These calculations are crucial for interpreting experimental results and maximising sensitivity to the EDM. A key aspect of the work is the development of a laser cooling scheme for BaF molecules, essential for reducing their velocity and achieving the required precision. Accurate knowledge of transition wavelengths and strengths, derived from the theoretical calculations, is vital for designing this scheme. The research also explores various trapping techniques, including optical and magnetic traps, to confine the cold BaF molecules. The challenges of collisional losses and heating within the traps are acknowledged, and strategies to mitigate these effects are discussed. The document details methods for producing a beam of BaF molecules, selecting molecules in specific quantum states, and detecting their properties. This work represents a significant step towards a highly sensitive search for the electron EDM using BaF molecules, potentially leading to a breakthrough in our understanding of fundamental physics.</p

Beam Molecules Trapped Using Photon Recoil

Researchers have developed a method for transferring molecules from a slow-moving beam directly into an optical trap using a single absorption and emission of a photon. This technique relies on manipulating the molecules’ energy states with an electric field to guide them into the trap, offering a new way to study cold molecules. The process is designed to capture molecules initially travelling at around 10 meters per second, bringing them to a standstill before transferring them into a trap cooled to approximately 7 millikelvin. The efficiency of this transfer has been carefully modelled, estimating that around 0.

Importantly, the team predicts this efficiency could be improved by a factor of 20 by precisely synchronizing the electric and magnetic fields with the molecules’ velocity. A key advantage of this method is its ability to accumulate molecules over time, building up a larger population within the trap due to the irreversible nature of the transfer process. This approach expands the range of molecules suitable for research, as it does not require the molecules to undergo laser cooling. By carefully controlling the electric field, the team demonstrated the ability to stop molecules travelling at speeds up to 14 meters per second, using a readily achievable electric field strength. This innovative method promises to unlock new possibilities for studying the properties and interactions of cold molecules, with potential applications in areas such as quantum information and fundamental physics.

Single-Photon Loading Traps Cold Molecules Effectively

This research presents a method for trapping molecules using a single absorption and emission of a photon, offering a pathway to study cold molecular species that are difficult to manipulate with traditional laser cooling techniques. The team estimates a loading efficiency of approximately 0. 04% for a typical decelerated beam of barium fluoride, potentially achieving around 880 molecules per trapping event. Importantly, the irreversibility of the loading process allows for the accumulation of larger numbers of molecules over time. This single-photon loading scheme broadens the scope of molecular research by circumventing the need for optical cycling, a requirement that restricts the types of molecules amenable to trapping and study. The ability to efficiently trap a wider range of complex molecular species opens new opportunities in areas such as cold molecular chemistry, quantum information science, and the investigation of fundamental interactions. Future work will likely focus on improving trap lifetimes and optimizing the synchronous modulation of external electric fields to enhance velocity selection and loading efficiency.