Ion traps – as the name suggests – trap ions. Once trapped, those ions can be precisely controlled and measured, which has all sorts of useful applications, including storing and processing quantum information.
In NPL’s ion trap, an ion starts life as a regular atom which is guided into the ion trap. There, a laser pulse knocks off an electron, turning it into a positively charged ion. The trap’s carefully arranged electrodes create an electric field which – because of the ion’s positive charge – can precisely levitate the ion in 3D space in the centre of the trap. The trap is contained within a vacuum, ensuring no particles can interfere with the ion.
This ion – and several others – are then cooled to very low energies using lasers. Lasers are used again to manipulate the ion’s energy state, measure it, or entangle it with other ions in a string, linking their states together.
Why put these poor ions through all this? Trapping ions has long been of interest to measurement scientists. Measuring the frequency of energy transitions creates the ultra-stable "ticks" of atomic clocks. Trapped ions are sensitive to tiny changes in electric and magnetic fields, making them perfect for sensing tiny variations in electronics and gravity.
But trapped ions are also promising for quantum computing.
The core of quantum computing is the quantum bit, or qubit. Certain particles – ions being one example – can be held in different energy states to represent 0 and 1, much like the binary bits in classical computing. But qubits can also exist in a superposition, of both 0 and 1 states at the same time. An ion in a trap can be manipulated with lasers to exist in a controlled superposition, with quantum coherence between the states, allowing it to represent multiple possibilities at once.
This ability to hold multiple possible states is what enables quantum computers to perform many calculations simultaneously. What’s more, entanglement between strings of ions enables computations that rely on the relationships between qubits, not just their individual states. Together, these features make quantum computers especially powerful for solving complex real-world problems, such as simulating chemical reactions, optimising global supply chains, or breaking advanced cryptographic codes. So ion traps are widely seen as a route to quantum processors.
NPL ion trap sparks interest at the NQCC
The NQCC new building was opened in October 2024 at the Harwell Science and Innovation Campus in Oxfordshire, with the goal of creating a UK capability in quantum computing. That remit includes providing academia and industry with access to emerging quantum technologies.
As such, it hosts multiple hardware and software systems with potential for quantum computing. Conversations between NPL and NQCC in mid 2023 identified that the NPL ion trap design could be a valuable research tool for advancing quantum computing. A joint application to the Government Office for Technology Transfer (GOTT) secured funding to transfer an NPL microtrap between the two government labs.
The journey from NPL to the NQCC
NPL has spent nearly 20 years developing this ion microtrap design – often in partnership with fabrication specialists at Kelvin Nanotechnology Ltd. It is a precision engineered, microfabricated device the size of a computer chip, mounted in secure packaging, a vacuum chamber, and positioned within a set of lasers and mirrors.
Alastair Sinclair, Principal Scientist in NPL’s microtraps team, notes “fabricating the device was extremely challenging. Standard fabrication techniques are well suited to two-dimensional microstructures, so we had to adapt some of these in unconventional ways to create a three-dimensional microstructure.”
Using a chip from an existing fabrication batch, NPL completed the final packaging, and integrated the optical and electrical systems to connect it to the NQCC’s systems. Prior to transfer, NPL tested it in their own labs, and hosted two knowledge transfer secondments to get the NQCC Ion Trap team up to speed on the trap. It was then transported to the NQCC, where it was set up and tested in NQCC labs. The first ions were trapped at the NQCC on Friday 28th March 2025.
The ion trap’s promising future at the NQCC
Now it is up and running, the ion trap provides a platform for the NQCC to explore how trapped ion systems can advance quantum computing.
One of their first research projects is exploring storing multiple qubits within the same atom. “The atom we're dealing with, strontium, offers three different ways to envision a qubit in the atomic level structure,” says Sinclair, “and NQCC is keen to investigate whether they can combine these three approaches. That could make running some quantum algorithms much more efficient.”
As it settles into its new home, the ion trap should mature as a research instrument. Eventually it could become a quantum computation device in its own right, on which academic and industrial partners can test their quantum algorithms – supporting NPL and NQCC’s goal of advancing UK capabilities in quantum technology.
But the project is about more than just technology. It is hoped the ion trap will bring NPL and the NQCC closer together and foster more collaborations. “NQCC has exciting plans for developing quantum computing capabilities that will benefit the UK” says Sinclair. “At NPL, within the ion trap team, we understand the quantum fundamentals behind quantum computing, and we know this ion trap system better than anyone. Together we can help to ensure that ion traps reach their full potential in the world of quantum computing.”
Dr Cameron Deans, Head of the Trapped-Ion Quantum Computing Team at the NQCC commented, “The NPL microtrap offers a well-understood mature research platform with which we can explore several directions in ion trap quantum computing. The GOTT funded partnership between the NQCC and NPL has proven to be a highly successful route to rapidly deploying this technology in the NQCC’s laboratories.”
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08 Jul 2025