Quantum Microscope Will Provide Superior Imaging Capabilities
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The QUASAR group at the University of Liverpool has been awarded funding from Innovate UK to develop a new type of microscope for non-destructive imaging of delicate structures. Building on the team’s previous breakthroughs, the quantum gas jet-based helium atom microscope (qHAM) will overcome some of the challenges associated with helium microscopy.
Technology Networks spoke to Professor Carsten Welsch, head of the Department of Physics at the University of Liverpool, to learn more about the new microscope and its development. In this interview, Carsten also highlights reasons behind the growing interest in quantum technologies and some of the hurdles faced when trying to exploit them.
Anna MacDonald (AM): Can you describe the principles of scanning helium microscopy and highlight some of the benefits that it can offer over other imaging technologies?
Carsten Welsch (CW): Scanning microscopes use a probing wave to scan the surface of an object, and the resolution has a number of physical limitations, determined by the nature of the particles in the beam.
It was Louis de Broglie who first proposed that matter has wave properties. As these types of wave have a much shorter wavelength than visible light, they can overcome the diffraction limit and enable study of features in the order of and maybe even below 1 μm.
The de Broglie wavelength is determined by the kinetic energy and the particle mass, but increasing the energy can destroy a delicate sample, so electron beams for example would not be suitable. Their charge would also make the analysis of samples with electric conductivity challenging.
Helium atoms provide a greater mass with an energy level similar to thermal energy, enabling a probe length scale down to an atomic level with a lower energy and provide surface scattering without penetrating the sample.
There have been other scanning helium microscopes, but these have been limited by the use of simple atom optics and existing detector technologies.
By using quantum technologies, we will be able to increase the contrast and the sensitivity of the detectors increasing the resolution. One central element of qHAM will be the creation of a strongly focused gas jet after an atom sieve – this shall pave the way for mm-resolution.
AM: What has limited greater use of this technology so far?
CW: One of the many challenges comes from finding an efficient way to focus the matter beam and detecting the scatter pattern. qHAM is designed to address these challenges and benefits from our expertise in these areas. It is very challenging to create well-defined and narrowly focused beams of neutral particles. We have been developing the underpinning technologies for more than a decade and are now in a good position to optimize these towards a range of applications.
CW: For more than a decade, my group has been developing least-invasive beam profile monitors to characterize beams of charged particles. These rely on the generation of a supersonic gas jet which is then shaped into a thin curtain before it crosses the primary particle beam to be analysed. The benefit of this technique is that the main particle beam is essentially unaffected by the measurement, i.e., the experiment or application can continue without any disturbance from the monitor.
Generating and shaping the gas jet is a significant challenge as it requires detailed simulation studies and years of experience in optimizing lab setups. We will now exploit two quantum effects – wave-particle duality and matter wave interference – to create a narrowly focused beam to scan a surface to be analyzed. As the scanning beam consists of neutral particles, we expect significant advantages compared to for example electron beams as this will allow to characterize conducting materials in detail – this is very important for a range of electronics developments or for studies into novel materials.
My group has an excellent track record in developing advanced technologies which we pioneered for fundamental physics experiments towards other applications. The helium microscope is another example where we see excellent potential outside of traditional accelerator science research.
AM: What applications do you expect the new microscope to have the most impact on?
CW: On the one hand, we think that it will give unprecedented insight into a range of materials and structures. We will push the technology to its limits so that the microscope can be made compact – this should make it interesting for many applications and in particular SMEs.
On the other hand, the required imaging and image analysis techniques are expected to be beneficial also for other areas – from the analysis of charged particle beams to medical imaging. We increasingly apply machine learning techniques and novel analysis algorithms in our instruments. Whilst these target one particle application initially – the helium microscope in this case – they usually are also of high interest for many other areas.
AM: Why is there so much interest in commercializing quantum technologies? What barriers are there to the commercial or industrial exploitation of quantum technologies?
CW: Quantum technologies show great promise in breaking through traditional technology barriers. In the case of the microscope, this concerns the achievable resolution as well as impact on the sample. We think that our technology can overcome existing barriers and provide superior imaging quality.
One challenge is that the underpinning technology is very challenging and takes significant expertise to be operated. Our project aims at simplifying all technologies concerned and identifying ways towards turn-key systems.
We will do this with established partners, in particular the company D-Beam which was spun out of the University of Liverpool and the Cockcroft Institute a few years ago with the aim of commercializing research outcomes. They also give us access to wider international markets and contribute their unique business expertise and imaging solutions.
Once we have demonstrated the helium microscope technology in principle, our aim is to work with D-Beam, other SMEs and research organizations on developing this cutting-edge technology into a market-ready product for a wide range of exciting applications.
Carsten Welsch was speaking to Anna MacDonald, Science Writer for Technology Networks.