Nanoscale ion microtrap array for quantum information processing

Possible basis of a future quantum processor chip
July 25, 2012

Microtrap chip (credit: NPL)

A groundbreaking new device from the UK’s National Physical Laboratory (NPL) could help to usher in the long-awaited era of quantum computers.

Researchers at NPL have demonstrated for the first time a monolithic 3D ion microtrap array that could be scaled up to handle several tens of ion-based quantum bits (qubits).

An ion trap is a combination of electric or magnetic fields that captures ions in a region of a vacuum the ions’ quantum state can be manipulated.

The research shows how it is possible to realize this device embedded in a semiconductor chip, and demonstrates the device’s ability to confine individual ions at the nanoscale.

As the UK’s national measurement institute, NPL is interested in how exotic quantum states of matter can be used to make high-precision measurements — for example, of time and frequency — ever more accurate. But the device could be used in quantum computation, where entangled qubits are used to execute powerful quantum algorithms. As an example, factorization of large numbers by a quantum algorithm is dramatically faster than with a classical algorithm.

Scalable ion traps consisting of a 2D array of electrodes have been developed, however 3D trap geometries can provide a superior potential for confining the ions. Creating a successful scalable 3D ion trapping device is based on the ability to scale the device to accommodate increasing numbers of atomic particles while preserving the trapping potential, which enables precise control of ions at the atomic level. Previous research resulted in compromising at least one of these factors, largely due to limitations in the manufacturing processes.

First monolithic ion microtrap array

The team at NPL has now produced the first monolithic ion microtrap array that uniquely combines a near-ideal 3D geometry with a scalable fabrication process, a breakthrough in this field. The microtrap chip outperforms all other scalable devices for ions.

Using a novel process based on conventional semiconductor fabrication technology, scientists developed the microtrap device from a silica-on-silicon wafer. The team were able to confine individual and strings of up to 14 ions in a single segment of the array. The fabrication process should enable device scaling to handle greatly increased numbers of ions while retaining the ability to individually control each of them.

The NPL device is a promising approach for advancing the scale of processor chips for ion-based qubits, according to Alastair Sinclair, Principal Scientist.

“We managed to produce an essential device or tool that is critical for state of the art research and development in quantum technologies. This could be the basis of a future atomic clock device, with relevance for location, timing, navigation services or even the basis of a future quantum processor chip based on trapped ions, leading to a quantum computer and a quantum information network.”