Long Working Distance Design for Cryogenic Quantum Research
To see quantum processes at ultra-low temperatures, cryogenic quantum research requires microscope optics. These optics' high resolution lets researchers study sensitive quantum states in imaging and spectroscopy.
Precision-engineered Long Working Distance lenses provide atomic-level accuracy for ion-trap and cryogenic quantum research.
Microscope Optics for Quantum Cryogenic Research
Essential Optics Functions Microscope optics must meet cryogenic quantum system requirements.
For imaging quantum materials and systems, typically down to the atomic level, objectives must have a high numerical aperture.
For ion trap quantum computers, Long Working Distance (LWD) goals are crucial. They ensure high-resolution fluorescence imaging and constant laser excitation in complex cryogenic and vacuum environments without damaging samples, vacuum chambers, or electrodes. Long Working Distance objectives have millimeter-to-centimeter working distances, while conventional objectives have less than 1 mm.
Microscopes need top and side optical access to support a variety of probes and sample manipulation tools.
Precision and Multi-Wavelength Performance: Quantum computing requires high-throughput laser excitation and weak fluorescence signals between 397 and 400 nm. Objectives need aberration-corrected optics for diffraction-limited resolution, minimal distortion, and chromatic aberration correction for UV laser and fluorescence.
Supported Advanced Methods
Specialised optics enable cutting-edge quantum research approaches like:
Quantum entanglement increases imaging sensitivity.
High-NA immersion objective lenses improve signal-to-noise ratios for Raman microscopy, allowing low-concentration molecule observations.
Quantum diamond microscopy uses nitrogen-vacancy (NV) centres in diamond to take high-resolution, non-destructive magnetic field images.
Challenges and Cryogenic Solutions
Integrating advanced optics with cryostages presents several thermal and mechanical stability challenges.
Integration: The design must incorporate advanced optics and cryostages for mechanical stability and ultra-low temperature maintenance. Cooling to the lowest temperatures requires these methods: Liquid nitrogen double-tilt stages provide atomic-resolution imaging and spectroscopy at intermediate and low temperatures.
At temperatures below 100 K, superconductivity requires liquid helium cooling.
Stability Improvements: Continuous cryogen flow, vibration decoupling, and other liquid helium stage advances enable steady, high-resolution imaging. Electron microscopy imaging systems must also be thermally stable (2 mK for hours).
Custom Long Working Distance UV Objective Lens Case Study
A case study of a customised Avantier UV objective lens for an ion-trap quantum computing research team shows the importance of Long Working Distance objectives in quantum computing.
Initial Challenges and Requirements Client needs objective lens for fluorescence imaging and laser delivery.
Client goals:
Project precise 1 µm laser dots for qubit control. Keep object plane distortion below 0.1 µm. Make sure UV transmittance (397–400 nm) is above 80%.
Met Obstacles:
The original design had 2.6 µm of distortion, which the client could not tolerate.
The technique showed heat sensitivity, shifting focus by 16 µm at 20-25 °C.
UV testing restrictions prevented direct evaluation of crucial metrics including the Modulation Transfer Function (MTF) and wavefront error at 397 nm.
Performance and Design Development
Generation 1 Lens
Despite attaining diffraction-limited performance, the first design failed to meet scaling requirements due to its narrow 300 µm x 40 µm FOV. Its vacuum NA was 0.5 and its working distance was beyond 50 mm.
Generation 2 Lens
Effects and Results
In addition to displaying 397 nm ion emission with high resolution and low distortion, the customised Long Working Distance UV objective lens produced precise 1–1.2 µm Gaussian UV dots.
The second-generation design's large FOV enabled multi-ion trapping and control, enabling scalable quantum structures. The lens's performance indicates how customised UV objective design can give optical accuracy for quantum computing by overcoming distortion, thermal effects, and field-of-view constraints.
