Saturday, March 16, 2024

New multimillion dollar research facility set to unlock secrets of quantum materials

UNIVERSITY OF BRITISH COLUMBIA

Material scientists from the University of British Columbia Stewart Blusson Quantum Matter Institute (Blusson QMI) will lead the development of a multi-million world-class crystal growth facility thanks to $5.8 million in investments by the Canada Foundation for Innovation (CFI) and the B.C. Knowledge Development Fund (BCKDF) announced today.

Blusson QMI Scientific Director Andrea Damascelli said the investment will strengthen Canada’s position as a leader in quantum research and technology.

“The investment enables the establishment of state-of-the-art research infrastructure that is unique in Canada and will deliver exceptional impact for quantum material design, technology development, and training of the quantum workforce,” said Damascelli.

Led by Blusson QMI Investigators Alannah Hallas and Doug Bonn, the new facility represents a total investment of $7.3 million-dollars, and will incorporate specialized apparatus designed for high-pressure synthesis.

“Just as the silicon age launched multiple trillion-dollar industries, the age of quantum materials is likely to foster intense economic development,” said Alannah Hallas.

“The new facility will accelerate this search by enabling us to synthesize quantum materials that have remained out of reach in the high-quality single crystal form that is needed to characterize them and ultimately fashion them into technological devices.”

To tune the formation and structure of new materials, scientists typically use methods that involve varying the temperature or the material’s chemical composition but can rarely significantly increase the pressure.

“Adding pressure as a third tuning parameter during synthesis will vastly expand the frontier across which we can discover novel quantum materials. At elevated pressures, materials can often form into new stable phases that are not accessible at lower pressures,” Hallas said. “A good example of this are diamonds that are formed as a result of squeezing carbon under extreme pressure and high heat.”

The new facility complements the characterization tools and theoretical expertise that already exist at UBC’s Blusson QMI, unlocking an end-to-end scientific workflow from the design and synthesis of new quantum materials to the elucidation of their properties and engineering prototype devices.

Under the direction of Hallas and Bonn, the lab incorporates five new material synthesis furnaces that will position researchers at UBC Blusson QMI and Canada at the forefront of realizing the technological promises of quantum materials.

Three of the five furnaces in the facility will be the first of their kind in the country, including Canada’s first high pressure floating zone furnace. Another high pressure furnace in the facility, known as an anvil press, will be, for the first time, dedicated to quantum materials discovery rather than geoscience.

The CFI Innovation Fund provides continued investments in infrastructure across the full spectrum of research, from the most fundamental to applied through to technology development. By investing in research infrastructure projects through the BCKDF, the B.C. government is continuing to support post-secondary institutions by improving productivity and competitiveness, and to move toward an innovative, sustainable and inclusive future.

Projects funded through the Innovation Fund and the BCKDF will help Canada and British Columbia remain at the forefront of exploration and knowledge generation while making meaningful contributions to generating social, health, environmental and economic benefits and addressing global challenges.

A new ion trap for larger quantum computers

ETH ZURICH

The experimental setup of the ETH researchers. The trap chip is located inside the container underneath the silver cupola, in which a lens captures the light emitted by the trapped ions. — IMAGE:
THE EXPERIMENTAL SETUP OF THE ETH RESEARCHERS. THE TRAP CHIP IS LOCATED INSIDE THE CONTAINER UNDERNEATH THE SILVER CUPOLA, IN WHICH A LENS CAPTURES THE LIGHT EMITTED BY THE TRAPPED IONS.
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CREDIT: ETH ZURICH / PAVEL HRMO

The energy states of electrons in an atom follow the laws of quantum mechanics: they are not continuously distributed but restricted to certain well-defined values – this is also called quantisation. Such quantised states are the basis for quantum bits (qubits), with which scientists want to build extremely powerful quantum computers. To that end, the atoms have to be cooled down and trapped in one place.

Strong trapping can be achieved by ionising the atoms, which means giving them an electric charge. However, a fundamental law of electromagnetism states that electric fields that are constant in time cannot trap a single charged particle. By adding an oscillating electromagnetic field, on the other hand, one obtains a stable ion trap, also known as a Paul trap.

In this way, it has been possible in recent years to build quantum computers with ion traps containing around 30 qubits. Much larger quantum computers, however, cannot straightforwardly be realised with this technique. The oscillating fields make it difficult to combine several such traps on a single chip, and using them heats up the trap – a more significant problem as systems get larger. Meanwhile transport of ions is restricted to pass along linear sections connected by crosses.

Ion trap with a magnetic field

A team of researchers at ETH Zurich led by Jonathan Home has now demonstrated that ion traps suitable for use in quantum computers can also be built using static magnetic fields instead of oscillating fields. In those static traps with an additional magnetic field, called Penning traps, both arbitrary transport and the necessary operations for the future super-computers were realized. The researchers recently published their results in the scientific journal Nature.

“Traditionally, Penning traps are used when one wants to trap very many ions for precision experiments, but without having to control them individually”, says PhD student Shreyans Jain: “By contrast, in the smaller quantum computers based on ions, Paul traps are used.”

The idea of the ETH researchers to build future quantum computers also using Penning traps was initially met with scepticism by their colleagues. For various reasons: Penning traps require extremely strong magnets, which are very expensive and rather bulky. Also, all previous realizations of Penning traps had been very symmetric, something that the chip-scale structures used at ETH violate. Putting the experiment inside a large magnet makes it difficult to guide the laser beams necessary for controlling the qubits into the trap, while strong magnetic fields increase the spacing between the energy states of the qubits. This, in turn, makes the control laser systems much more complex: instead of a simple diode laser, several phase-locked lasers are needed.

Transport in arbitrary directions

Home and his collaborators were not deterred by those difficulties, however, and constructed a Penning trap based on a superconducting magnet and a microfabricated chip with several electrodes, which was produced at the Physikalisch-Technische Bundesanstalt in Braunschweig. The magnet used delivers a field of 3 Tesla, almost 100’000 times stronger than Earth’s magnetic field. Using a system of cryogenically cooled mirrors, the Zurich researchers managed to channel the necessary laser light through the magnet to the ions.

The efforts paid off: a single trapped ion, which can stay in the trap for several days, could now be moved arbitrarily on the chip, connecting points “as the crow flies” by controlling the different electrodes – this is something not previously possible with the old approach based on oscillating fields. Since no oscillating fields are needed for trapping, many of those traps can be packed onto a single chip. “Once they are charged up, we can even completely isolate the electrodes from the outside world and thus investigate how strongly the ions are disturbed by external influences”, says Tobias Sägesser, who was involved in the experiment as a PhD student.

Coherent control of the qubit

The researchers also demonstrated that the qubit energy states of the trapped ion could also be controlled while maintaining quantum mechanical superpositions. Coherent control worked both with the electronic (internal) states of the ion and the (external) quantised oscillation states as well as for coupling the internal and external quantum states. This latter is a prerequisite for creating entangled states, which are important for quantum computers.

As a next step, Home wants to trap two ions in neighbouring Penning traps on the same chip and thus demonstrate that quantum operations with several qubits can also be performed. This would be the definitive proof that quantum computers can be realized using ions in Penning traps. The professor also has other applications in mind. For instance, since the ions in the new trap can be moved flexibly, they can be used to probe electric, magnetic or microwave fields near surfaces. This opens up the possibility to use these systems as atomic sensors of surface properties.

Moving a single trapped ion in a two-dimensional plane and illuminating it with a laser beam allows the researchers to create the ETH logo. The image is formed averaging over many repetitions of the transport sequence.

CREDIT

(Photograph montage: ETH Zurich / Institute for Quantum Electronics)

JOURNAL

Nature

DOI

10.1038/s41586-024-07111-x

ARTICLE TITLE

Penning micro-trap for quantum computing

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