Skip to main content

Superfluid helium-3 research helps assess the feasibility of topologically protected quantum computation.

Superfluid helium-3 research helps assess the feasibility of topologically protected quantum computation.

  • Date12 March 2021

Research on mesoscopic superfluid helium-3 demonstrates the fragility of surface-bound states, an important step in the quest to identify and harness Majorana fermions.

2021 03 12  Superfluid helium-3 research helps assess the feasibility of topologically protected quantum computation

One of the key objectives of the second quantum revolution is to build a quantum computer that is fault tolerant. So far the qubits are not up to the job; the lifetime of a quantum state used to encode information is just too short. Solving this problem is a long-term materials challenge and internationally a major strategic research priority.

A radically different and more speculative approach, one supported by Microsoft, is so called topological quantum computing. This involves creating a system which hosts Majorana fermions - particles which are their own antiparticles - and manipulating them for quantum computation.

The superfluid state of liquid helium-3 exists within few thousandths of a degree from absolute zero. It provides a benchmark for the class of materials (topological superconductors) from which such a computer would be built. While helium-3 forms a topological superfluid, topological superconductivity has yet to be conclusively demonstrated in any material or system. There is theoretical understanding that Majorana fermions exist in superfluid helium-3, as topologically protected zero-energy bound states at the surfaces or interfaces.

The London Low Temperature Laboratory at Royal Holloway, University of London has pioneered a range of new techniques which allow the study of superfluid helium-3 films, cooled to ultralow temperatures.  Central to our approach is the confinement of the liquid in precisely engineered slab-like cavities in silicon, using sophisticated nanofabrication methods. To probe the surface effects effectively, these films need to be as thin as the size of the helium-3 atomic pairs that lie at the heart of superfluidity.

Helium-3 is a system of pristine purity and allows exquisite control over the surfaces. This is done by isotopic tuning, in which helium-4 can be used to replace helium-3 in the helium surface boundary layer, which is a few atomic layers thick. In the article published in Nature Communications, the authors show that fine tuning the surface scattering conditions allows selecting the level of suppression of superfluidity under confinement. Particularly, switching on the magnetic scattering channel leads to an unexpectedly large level of suppression, indicating an increase of the density of unprotected zero-energy Andreev bound states. These discoveries pave a way towards accurate control and identification of surface-bound states in helium-3 systems and the building of hybrid mesoscopic devices using helium-3 superfluids.

Dr Petri Heikkinen, the corresponding author of the article, concludes: “Our recent work demonstrates the fragility of surface-bound states to exactly how helium-3 scatters from the surfaces. We believe that our result is a crucial step in the quest to identify and harness Majoranas in liquid helium-3.”

The experiments were carried out by the Quantum Fluids and Solids group at Royal Holloway, University of London, using nanofluidic cavities fabricated at the Cornell University (Parpia's group). Theoretical calculations and modelling were performed by researchers at the Montana State University and at the Indian Institute of Science. Research was supported at Royal Holloway by EPSRC. The London Low Temperature Laboratory at Royal Holloway, University of London is part of the European Microkelvin Platform, a European Infrastructure.

Article: P. J. Heikkinen, A. Casey, L. V. Levitin, X. Rojas, A. Vorontsov, P. Sharma, N. Zhelev, J. M. Parpia, and J. Saunders: Fragility of surface states in topological superfluid 3He. Nature Communications

Related topics

Explore Royal Holloway

Get help paying for your studies at Royal Holloway through a range of scholarships and bursaries.

There are lots of exciting ways to get involved at Royal Holloway. Discover new interests and enjoy existing ones

Heading to university is exciting. Finding the right place to live will get you off to a good start

Whether you need support with your health or practical advice on budgeting or finding part-time work, we can help

Discover more about our 21 departments and schools

Find out why Royal Holloway is in the top 25% of UK universities for research rated ‘world-leading’ or ‘internationally excellent’

Royal Holloway is a research intensive university and our academics collaborate across disciplines to achieve excellence.

Discover world-class research at Royal Holloway

Discover more about who we are today, and our vision for the future

Royal Holloway began as two pioneering colleges for the education of women in the 19th century, and their spirit lives on today

We’ve played a role in thousands of careers, some of them particularly remarkable

Find about our decision-making processes and the people who lead and manage Royal Holloway today