Quantum-Optimal Stark Deceleration: A Leap Forward in Cold Molecular Control

Our team member, Dr. Emil Żak continues to make significant contributions to quantum innovation, consistently pushing the boundaries of molecular quantum control through groundbreaking research and interdisciplinary collaboration.

Cold molecules represent a powerful resource for quantum technologies, enabling precise quantum state manipulation and novel applications in chemistry and physics. A significant challenge in harnessing cold molecules is the production of slow, controlled molecular beams. A recent paper proposes a quantum-optimized Stark deceleration method, introducing significant enhancements in controlling molecular quantum states and motion. Improved molecular beam control has extensive implications, including applications in precision quantum research, quantum computing and ultracold collision experiments. 

Advanced Quantum-Chemistry and Quantum Molecular Dynamics Simulations

The research focuses on ammonia (NH₃), chosen for its favorable quantum state properties. The team, involving researchers from Center for Free-Electron Laser Science at Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany, performed high-accuracy quantum-chemical calculations to model ammonia's response to dynamic electric fields precisely. Using these insights, quantum dynamics simulations produced optimized state transitions between ammonia's weak-field-seeking (WFS) and strong-field-seeking (SFS) states.

The simulation results were exceptional, demonstrating state transfer efficiencies above 99.5%. This improved method significantly increases molecular deceleration efficiency and extends the effective range of molecular velocities and positions that can be manipulated.

Figure. Phase-space evolution (cooling) of molecular beams of ammonia molecules inside Stark Decelerator.

Stark-Chirped Rapid Adiabatic Passage (SCRAP) Technique

The core innovation involves embedding Stark-Chirped Rapid Adiabatic Passage (SCRAP) directly into the Stark deceleration structure. Conventionally, SCRAP requires external lasers and fields to achieve robust quantum state transitions. However, this method ingeniously utilizes the decelerator’s existing electric fields to perform SCRAP, significantly simplifying the setup and enhancing robustness against field imperfections and molecular velocity variations.

Synchronizing laser pulses and timed electric fields continuously reduces molecular kinetic energy, creating a consistent uphill Stark potential. This greatly enhances the efficiency of slowing molecules, resulting in colder, denser molecular beams.

Figure. Population transfer efficiency inside the new Stark Decelerator design.

Proposed Hybrid Stark Decelerator:
Molecular Dynamics Studies

The authors introduce a hybrid Stark decelerator design that combines laser-induced quantum state control with optimized electric fields. This advanced device design allows precise, coherent state manipulation throughout the deceleration stages. The flexibility and efficiency provided by this hybrid approach enable the selective preparation of molecular beams tailored to specific experimental needs. Through extensive molecular dynamics simulations, the paper demonstrates enhanced phase-space bunching of molecular beams and improved efficacy in slowing ammonia molecules.

This new technique is broadly applicable to various polar molecules, enhancing the potential impact and versatility of Stark deceleration technology.

Figure. Phase space diagrams and time-of-flight plots simulated with Molecular Dynamics for ammonia, comparing the new design (AS/ASMP) with the standard Stark Deceleration (AG). 

Grounding BEIT’s Molecular Dynamics and Quantum Chemistry Expertise and Research Leadership

The project, led by Dr Emil Żak, presently Head of Quantum Algorithms at BEIT, demonstrates innovative integration of quantum mechanics, control theory, and practical experimental design, reflecting deep interdisciplinary expertise that significantly propels the field forward.

This work demonstrates BEIT’s state-of-the-art expertise in Molecular Quantum and Classical Dynamics simulations, further grounding our qualifications in the development of our products: WaferMol and BDocker. 

Check out the full paper here