Scientists demonstrate new combination of materials for quantum science

Quantum information scientists are constantly searching for the best combination of materials that can be manipulated at the molecular level to reliably store and transmit information. Following recent proof-of-principle demonstrations, researchers are adding new combinations of compounds to the list of quantum materials.

In a study reported in ACS PhotonicsThe researchers combined two nanosized structures, one made of diamond and one made of lithium niobate, on a single chip. They then sent light from the diamond to the lithium niobate and measured the percentage of light that successfully traveled.

The larger this ratio, the more efficient the material’s bonding and the more promising the pairing as a component of a quantum device.

As a result, an astounding 92% of the light was converted from diamond to lithium niobate.

This research was supported in part by Q-NEXT, the U.S. Department of Energy’s (DOE) National Quantum Information Science Research Center led by Argonne National Laboratory. Amir Safavi-Naini and Jelena Vukovic of Stanford University led the study.

“We got an impressive 92% efficiency from this device,” said study co-author Hope Lee, a Ph.D. He is a student at Stanford University and a researcher who collaborated with Q-NEXT director David Orshalom during his undergraduate years at the University of Chicago. “We have shown the benefits of the platform.”

A little bit about qubits

Quantum technology exploits special features of matter at the molecular scale to process information. Quantum computers, networks, and sensors are expected to have a significant impact on our lives in fields such as medicine, communications, and logistics.

Quantum information is delivered in packets called qubits. Qubits come in many forms. In the research team’s new platform, qubits transmit information as particles of light.

Reliable qubits are important for technologies such as quantum communication networks. Similar to traditional networks, information in a quantum network moves from one node to another. Stationary qubits store information within their nodes. Flying qubits carry information between nodes.

The research team’s new chip will form the basis of a stationary qubit. The more robust the stationary qubits, the more reliable the quantum network and the longer the distance the network can cover. A continent-spanning quantum network is well within reach.

material advantages

Diamonds have long been touted as an excellent home for qubits. One is that diamond’s molecular structure can be easily manipulated to host fixed qubits. Second, diamond-hosted qubits can retain information for relatively long periods of time, meaning that calculations take longer to run. Additionally, calculations performed using diamond-hosted qubits exhibit high accuracy.

Diamond’s partner in the group’s research, lithium niobate, is also a star performer when it comes to processing quantum information. Its special properties allow scientists to change the frequency of light that passes through it, giving it versatility.

For example, researchers can apply electric fields or mechanical strains to lithium niobate to tune the direction of light. It is also possible to reverse the orientation of the crystal structure. Doing this at regular intervals is another way to shape the passage of light through the material.

“These properties of lithium niobate can be used to transform and modify the light emitted by diamond, modulating it in ways that are useful for a variety of experiments,” said study co-author and Ph.D. Jason Herman said. Student at Stanford University. “For example, you can basically convert light into frequencies used in existing communications infrastructure. So these properties of lithium niobate are very beneficial.”

strong pairing

Traditionally, light from diamond-hosted qubits is sent either through fiber optic cables or into free space. In both cases, the experimental setup is cumbersome. Fiber optic cables are long, dangling and dangling. Sending qubits into free space requires large equipment.

All such devices disappear when the light from a diamond qubit is directed into lithium niobate instead. Almost all components can be placed on one small chip.

“There are advantages to having as many devices and functions as possible on a single chip,” Lee said. “It’s more stable. And you can really downsize your setup.”

Not only that, but the two devices are connected by a very thin filament, 1/100th the width of a human hair, which forces the quantum light into a narrow passageway leading to the lithium niobate, allowing the light to interact with the material. will increase. You can now easily manipulate light properties.

“When all the different light particles interact within such a small volume, the conversion process becomes much more efficient,” Herrmann said. “Being able to do this on an integrated platform is expected to result in significant efficiency gains compared to setups using fiber or free space.”

Challenging assembly

One of the challenges in developing this platform was manipulating the diamond, which is only 300 nanometers wide, to align with the lithium niobate.

“I had to poke and move the diamond with a little needle until it looked like it was in the right place on this plate,” Lee said. “It’s like being poked with small chopsticks.”

Measuring the transmitted light was also a painstaking process.

“In order to be able to say, ‘This is all the transfer from the diamond to the lithium niobate,’ you have to make sure you account for all the places where the light travels or gets lost,” Herrmann said. “That calibration measurement went back and forth a lot to make sure it was done correctly.”

The research team plans further experiments that take advantage of the quantum information provided by diamond and lithium niobate, both separately and together. Their recent success is just one milestone in what he hopes will be a diverse menu of devices based on the two materials.

“We’re showing that by combining these two material platforms and directing light from one to the other, you can actually get the best of both worlds, rather than just working with one material,” Lee said. Masu.