Engineers Design Nanostructured Diamond Metals for Compact Quantum Technologies


Penn engineers design nanostructured diamond metals for compact quantum technologies

By finding a certain type of defect inside a diamond block and shaping a nanometric pillar pattern on the surface above it, researchers can control the shape of individual photons emitted by default. Because these photons contain information on the spin state of an electron, such a system could be used as a basis for compact quantum technologies. Credit: Ann Sizemore Blevins

At the chemical level, diamonds are no more than carbon atoms aligned in a precise three-dimensional (3D) crystal lattice. However, even a seemingly perfect diamond contains flaws: spots in this network where a carbon atom is missing or has been replaced by something else. Some of these defects are highly desirable; they trap individual electrons capable of absorbing or emitting light, thus causing the various colors of diamond gemstones and, more importantly, creating a platform for various quantum technologies for 39, advanced computing, secure communication and precision detection.

Quantum technologies rely on quantum information units called qubits. The spin of electrons are the first candidates to serve as qubits; unlike binary computer systems where data takes only the form of 0 or 1, the electron spin can represent information in the form 0, 1 or both simultaneously in a quantum superposition. Diamonds are of particular interest to quantum scientists because their quantum mechanical properties, including superposition, exist at room temperature, unlike many other potential quantum resources.

The practical challenge of collecting information from a single atom deep within a crystal is however discouraging. Penn's engineers addressed this problem in a recent study in which they developed a way to model the surface of a diamond that facilitates the collection of light from internal defects. Called metalens, this surface structure contains features at the nanoscale that bend and focus the light emitted by the defects, although they are actually flat.

The research was conducted by Lee Bassett, Assistant Professor, Department of Electrical Engineering and Systems, graduate student Tzu-Yung Huang, and postdoctoral researcher Richard Grote of Bassett's laboratory.

Additional members of the Bassett Lab, David Hopper, Annemarie Exarhos and Garrett Kaighn, contributed to the work, as did Gerald Lopez, Business Development Director of the Singh Center for Nanotechnology, and two members of the Center for Nanophotonics of Amsterdam, Sander. Mann and Erik Garnett.

The study was published in Nature Communications.

To exploit the potential power of quantum systems, it is essential to be able to create or find structures that can reliably manipulate and measure the electron spin, a difficult task given the fragility of quantum states.

<div data-thumb = "" data-src = "https: // net / newman / gfx / news / 2019/9-pennengineer.jpg "data-sub-html =" Metal researchers, which consist of many small nanopilliers, roughly assess the effect of a Fresnel lens on light Directly a diamond holiday center (NV) in an optical fiber, eliminating the need for a bulky microscope. Nature Communications">

<img src = "" alt = "Penn Engineers Design Nanostructured Diamond Metals for Compact Quantum Technologies” title=”The researchers' metalens, composed of numerous small nanopillaries, roughly calculate the effect of a Fresnel lens to direct the light of a nitrogen non-presence (NV) center onto an optical fiber, eliminating the need for a bulky microscope. Credit: Nature Communications“/>

The researchers' metalens, composed of numerous small nanopillaries, roughly calculate the effect of a Fresnel lens to direct the light of a nitrogen non-presence (NV) center onto an optical fiber, eliminating the need for a bulky microscope. Credit: Nature Communications

Bassett's lab addresses this challenge from a number of perspectives. Recently, the laboratory has developed a quantum platform based on a two – dimensional (2D) material called hexagonal boron nitride which, because of its extremely thin dimensions, allows easier access to electron spins. In this study, the team returned to a 3D material that contains natural imperfections offering great potential for controlling electron spins: diamonds.

The small defects of diamonds, called vacant nitrogen centers, are known to harbor electron spins that can be manipulated at room temperature, unlike many other quantum systems that require temperatures close to absolute zero. . Each NV center emits a light that provides information on the quantum state of the spin.

Bassett explains why it is important to consider the 2-D and 3-D pathways of quantum technology:

"The different material platforms are at different levels of development and will ultimately be useful for different applications.Flaws in 2D materials are ideally suited for proximity sensing on surfaces and could possibly prove to be beneficial for d & # 39; Other applications, such as integrated quantum photonic devices, "says Bassett. "At the moment, however, the Diamond NV Center is simply the best platform for the processing of quantum information at room temperature, and it is also a prime candidate for the construction of large-scale quantum communication networks. "

Up to now, it has been possible to achieve the combination of desirable quantum properties required for these demanding applications by using NV centers deeply embedded in 3D diamond crystals in bulk.

Unfortunately, these deeply rooted NV centers can be difficult to access because they are not on the surface of the diamond. The collection of light from these hard-to-reach defects usually requires a bulky optical microscope in a highly controlled laboratory environment. The Bassett team wanted to find a better way to collect light from the NV centers, a goal they were able to achieve by designing a specialized metal that avoids the need for a large expensive microscope.

"We used the concept of metasurface to design and fabricate a structure on the surface of the diamond that acts as a lens to collect the photons of a single quarter of a diamond and direct them to an optical fiber, while that. before that it required a large free space optical microscope, "says Bassett. "This is a key first step in our broader effort to achieve compact quantum devices that do not require a room filled with electronics and free-space optical components."

Penn engineers design nanostructured diamond metals for compact quantum technologies

Tzu-Yung Huang, Lee Bassett and David Hopper at Work at Bassett's Quantum Engineering Lab. Credit: University of Pennsylvania

Metasurfaces are made up of intricate patterns on the nanoscale, capable of realizing physical phenomena otherwise impossible on a macroscopic scale. Researchers use a field of columns 1 micrometer in diameter and 100 to 250 nanometers in diameter, arranged to focus the light in the same way as a traditional curved lens. Engraved on the surface of the diamond and lined up at one of the NV centers located in the interior, the metalens guide the light that represents the spin state of the electron directly into an optical fiber , which simplifies the process of data collection.

"The size of the metals is about 30 microns in diameter, which corresponds to the diameter of a hair.If you look at the diamond on which we made it, you can not see it. At most, you can see a black shimmer, "says Huang. "We generally think that lenses focus or collimate, but with a metastructure, we have the freedom to design any type of profile we want.This gives us the freedom to adapt the emission pattern or the profile of a quantum transmitter, such as an NV center, which is impossible or very difficult with free-space optics. "

To design their metals, Bassett, Huang and Grote had to form a team with a wide range of knowledge, from quantum mechanics to electrical engineering, to nanotechnology. Bassett believes that the Singh Center for Nanotechnology plays a vital role in its ability to physically build metals.

"Nanofabrication was a key part of this project," says Bassett. "We had to do a high-resolution lithography and precise engraving to make a set of diamond nanopillters at scales shorter than the wavelength of light.The diamond is a difficult material to deal with. It was Richard's dedicated work at the Singh Center, which allowed us to have the chance to count on the experienced cleanroom staff, and Gerald helped us develop electron beam lithography techniques. we have also benefited from the help of Meredith Metzler, responsible for the thin layer at the Singh center, to develop diamond engraving. "

While nanofabrication has its challenges, the flexibility offered by metasurface engineering offers significant advantages for real quantum technology applications:

"We have decided to collimate the light from NV centers to switch to an optical fiber, because it easily interfaces with other techniques developed for compact optical fiber technologies over the last decade" Huang said. "Compatibility with other photonic structures is also important, you may want to put other structures on the diamond, and our metals do not prevent us from benefiting from these other optical enhancements."

This study is just one of many steps towards the goal of compacting quantum technology into more efficient systems. Bassett's lab plans to continue to look for the best way to exploit the quantum potential of 2D and 3D materials.

"The field of quantum engineering is advancing rapidly, thanks largely to the convergence of ideas and expertise from many disciplines, including physics, materials science, photonics, and electronics. "said Bassett. "Penn Engineering excels in all of these areas, so we look forward to many breakthroughs in the future, and ultimately want to transfer this technology from the lab to the real world where it could affect our daily lives."

Engineers develop two-dimensional room temperature platform for quantum technology

More information:
Tzu-Yung Huang et al., A monolithic immersion metal for the imaging of quantum emitters in the solid state, Nature Communications (2019). DOI: 10.1038 / s41467-019-10238-5

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Engineers Design Nanostructured Diamond Metals for Compact Quantum Technologies (June 11, 2011)
recovered on June 11, 2019

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