“Thanks to this elaborate structure in their nasal cavities, Arctic seals lose less heat through nasal heat exchange than subtropical seals when both are exposed to the same conditions,” says corresponding author and physical chemist Signe Kjelstrup of the Norwegian University of Science and Technology. “This provides an evolutionary advantage, especially in the Arctic where heat loss is energy dissipation, which must be replenished by food.”

“What’s so amazing is that these Arctic seals retain 94% of the water when they breathe in and out,” says Kjelstrup. “This means that most of the water added to the air during inhalation is then recovered during exhalation.”

In cold, dry environments, animals lose heat and moisture just by breathing. Most mammals and birds have complex bones called maxilloturbinates inside their nasal cavities that help to minimize this risk. These porous, bony shelves are covered with a richly vascularized layer of mucosal tissues that warm and humidify inhaled air, which is important for lung function, and reduce the amount of heat and moisture lost during exhalation.

The structure of these bones varies between species, however. Kjelstrup’s team previously showed that reindeer noses enable efficient heat exchange in cold conditions, but because reindeer don’t live in diverse environments, they turned to seals to test whether there’s anything special about the noses of Arctic animals.

“You can’t find reindeer in the middle of the Mediterranean, but seals live in many different environments, so they allowed us to test this question,” says Kjelstrup. “And we knew from a previous study that Arctic seal noses are sponge-like and very dense, whereas the Mediterranean seal nose has a more open structure.”

The researchers used computer tomography to make 3D models of the nasal cavities/maxilloturbinates of an Arctic species of seal, the bearded seal (Erignathus barbatus), and a subtropical species, the Mediterranean monk seal (Monachus monachus). Then, they used energy dissipation models to compare the seals’ ability to warm and moisten air during inhalation and to reduce heat and moisture loss during exhalation. The team tested both seals under Arctic conditions (−30°C), and at 10°C, which would represent a cold day for a Mediterranean monk seal. They also tweaked different parameters within the model to identify geometrical features of the nasal cavity that are important for its function.

The model indicated that Arctic seals are much more efficient than subtropical seals at retaining heat and water exchange in both Arctic and Mediterranean ambient temperatures. At −30°C, the subterranean seals lost 1.45 times as much heat and 3.5 times as much water per breath cycle as the Arctic seals, and at 10°C, the subterranean seals lost 1.5 times as much heat and 1.7 times as much water.

This advantage was due to the Arctic seal’s more complex, dense nasal cavity. Specifically, the researchers showed that the increased perimeter of the Arctic seal’s maxilloturbinates is key to limiting energy dissipation at low ambient temperatures.

The study investigated moisture and heat loss per breath cycle (i.e., for one inhalation and exhalation), but the role of breathing rate remains unclear. This is especially complicated for seals, who pause their breathing for minutes at a time when they dive.

In the future, the researchers hope to study the nasal structures of other species to see if different structures provide evolutionary advantages in other environments. “The camel, for instance, doesn’t need to save much on heat, but it does need to save on water, so one may speculate that it could tell us something about relative importance of the two,” says Kjelstrup.

Ultimately, the researchers plan to use this information to engineer more efficient heat exchangers and ventilation systems. “If nature manages to create such great heat exchangers, I think we should copy that in engineering to create more efficient processes, for instance, in air conditioners,” says Kjelstrup.

This research was supported by the Research Council of Norway and the Tromsø Research Foundation.

Following a recent proof-of-principle demonstration, researchers are adding a new combination of compounds to the quantum materials roster.

In a study reported in ACS Photonics, researchers combined two nanosized structures — one made of diamond and one of lithium niobate — onto a single chip. They then sent light from the diamond to the lithium niobate and measured the fraction of light that successfully made it across.

The greater that fraction, the more efficient the coupling of the materials, and the more promising the pairing as a component in quantum devices.

The result: An extraordinary 92% of the light made the jump from diamond to lithium niobate.

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

“It was an exciting result to get 92% efficiency from this device,” said Hope Lee, paper co-author and a Ph.D. student at Stanford University and researcher who worked with Q-NEXT Director David Awschalom while an undergraduate at the University of Chicago. “It showed the advantages of the platform.”

A bit about qubits

Quantum technologies harness special features of matter at the molecular scale to process information. Quantum computers, networks and sensors are expected to have an enormous impact on our lives in areas such as medicine, communication and logistics.

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

Reliable qubits are critical for technologies such as quantum communication networks. As in traditional networks, information in quantum networks travels from one node to another. Stationary qubits store information within a node; flying qubits carry information between nodes.

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

A material advantage

Diamond has long been touted as a great home for qubits. For one, diamond’s molecular structure can be easily manipulated to host stationary qubits. For another, a diamond-hosted qubit can maintain information for a relatively long time, meaning more time for performing computations. Also, computations performed using diamond-hosted qubits exhibit high accuracy.

Diamond’s partner in the group’s study, lithium niobate, is another star performer when it comes to processing quantum information. Its special properties give scientists versatility by allowing them to change the frequency of the light passing through it. For example, researchers can apply an electric field or a mechanical strain to the lithium niobate to adjust how it channels light. It’s also possible to flip the orientation of its crystal structure. Doing this at regular intervals is another way to shape light’s passage through the material.

“You can use these properties of the lithium niobate to convert and change the light coming from the diamond, modulating it in ways that are useful for different experiments,” said Jason Herrmann, paper co-author and a Ph.D. student at Stanford. “For instance, you can basically convert the light into a frequency used by existing communications infrastructure. So those properties of lithium niobate are really beneficial.”

A powerful pairing

Traditionally, light from diamond-hosted qubits is channeled into either a fiber-optic cable or free space. In both cases, the experimental setup is unwieldy. Fiber-optic cables are long, dangly and floppy. And transmitting qubits into free space requires bulky equipment.

All that equipment goes away when light from the diamond’s qubits is instead channeled into lithium niobate. Nearly every component can be placed on one tiny chip.

“There’s an advantage to having as many of your devices and your functionalities as possible on a single chip,” Lee said. “It’s more stable. And it really allows you to miniaturize your setups.”

Not only that, but because the two devices are connected by a whisper-thin filament — 1/100 of the width of a human hair — the quantum light is squeezed into the narrow passage that leads to lithium niobate, increasing the light’s interaction with the material and making it easier to manipulate light’s properties.

“When all the different light particles are interacting together in such a small volume, you get a much higher efficiency in the conversion process,” Herrmann said. “Being able to do this in the integrated platform will hopefully give rise to much higher efficiencies compared to the setup with fibers or free space.”

A challenging assembly

One of the challenges of developing the platform was manipulating the diamond — a mere 300 nanometers wide — to align with the lithium niobate.

“We had to poke at the diamond with tiny little needles to shift it around until it visibly looked like it was in the correct spot on this plate,” Lee said. “It’s almost like you’re poking at it with little chopsticks.”

Measuring the transferred light was another painstaking process.

“We have to really make sure we’re accounting for all the places where light is transmitted or lost to be able to say, ‘This is how much is going from diamond to lithium niobate,'” Herrmann said. “That calibration measurement took a lot of back and forth to make sure we were doing it correctly.”

The team is planning further experiments that leverage the quantum-information advantages offered by diamond and lithium niobate, both separately and together. Their latest success is only one milestone in what they hope will be a diverse menu of devices based on the two materials.

“By putting these two material platforms together and channeling light from one to the other, we show that, instead of working with just one material, you can really have the best of both worlds,” Lee said.

This work was supported by DOE’s Office of Science National Quantum Information Science Research Centers as part of the Q-NEXT center. It was also supported by the U.S. National Science Foundation and the Swiss National Science Foundation.