Backbone nodes are a kind of node within a quantum network. They serve as central hubs of communication, connecting all the end-user nodes within the network. They are responsible in directing and relaying quantum information between the different end user nodes. Backbone nodes tend to be more complex and sophisticated than the nodes used by end users and require special technology, like quantum repeaters to guarantee the safe and reliable transfer of quantum information.
The fundamental component of quantum repeaters is a memory qubit that connects to light. The qubit captures the information stored on light, then keeps it in memory, and along with other qubits nearby and qubits, corrects errors to correct any mistakes that could have occurred during the communication. To be able to function, memory qubits have to be able to perform solid interactions with light in the telecom or visible domain (ruling out the majority of most popular qubit candidates for quantum computations, such as quantum qubits that conduct electricity) and, ideally, be able to manufacture in mass quantities. This makes defect qubits similar to color centers found in diamond, the most popular candidates for quantum repeater memories.
The term “memory qubit” is an quantum bit (qubit) designed and made to keep and retrieve quantum information. In quantum computing, data is processed through manipulating the state of qubits that can be superposition of several states simultaneously. But keeping the coherence between these superpositions is a challenge because of the decoherence effects induced through interactions with external environment.
Memory qubits have been designed to have a greater coherence time than other qubits. This is why they are ideal to be used for the storage and retrieval of quantum information over longer intervals of time. They can be made by various physical systems like trapped ions, superconducting circuits or nitrogen vacancy centers within diamond.
It’s defective, but it’s not broken
Defects found in solids constitute the most diverse of qubits, which are composed of an atom or two that form the defect within an solid, uniform material. The kind of atom and the material being used the qubit is derived as a result of the magnetic or electronic conditions of the affected atom(s). Qubits with defects are present in a variety of materials naturally and often are manufactured by the precise implanting of a host that contains the defect of your choice. Although a wide range of materials are capable of hosting defects qubits the search for a defect-material pair with a specific set of properties is an arduous task.
Diamond is among the most fascinating materials. Diamond is made up of carbon atoms in a lattice is the strongest natural substance in the world it has the broadest optical transmission and is the highest naturally found thermal conductor. It’s durable in environments that range from the deepest and coldest vacuums to extremely high temperatures and pressures and is able to be included in living systems. Natural diamonds form deep within the earth due to the result of tectonic pressures that are 100s of kilometers below surface of the earth. The diamonds that form due to their unique growth environment they are diverse and distinctive. While they’re more pure than other crystals, diamonds have different impurities that are absorbed from the surrounding environment during the lengthy slow process of growth. These impurities are the reason that gives diamonds their diverse shades they range between deep blue and vibrant pink. However, in certain instances diamond imperfections are more than just making them stunning and unique and beautiful. They can also serve as amazing qubits in quantum networks.
Diamond is home to a variety of imperfections, but two classes of diamond defects are emerging as the most suitable possibilities for communication uses: The Nitrogen-Vacancy (NV) in addition to the Silicon-Vacancy Center (SiV). Both NV as well as the SiV are created by the removal of the two adjoining Carbon atoms from the diamond crystal lattice then replacing them by one Nitrogen and a Silicon atom, and vice versa.
A diamond crystal lattice an extremely symmetrical arrangement of carbon atoms inside the diamond crystal. The diamond crystal lattice an intricate three-dimensional web made up of carbon atoms which are interconnected by covalent bonds. This lattice arrangement is each carbon atom is connected to four carbon atoms in the vicinity and forms a tetrahedral structure.
Diamond crystals is renowned for its extraordinary toughness, thermal conductivity that is high and optical properties like the high index of refractive and dispersion. It is used extensively for the manufacture of cutting tools and jewelry and in industrial applications like heat sinks, high pressure anvils or electronic gadgets.
Diamond’s atomic defects alter the way they interact with light. In this case is the Element Six high purity PECVD-grown diamond is infused by the SiV (top left) along with the NV (bottom right) and then is annealed. When exposed to green light, areas of diamond that are pure (left) are then not emitting light. However, regions with imperfections emit various levels of red light creating the image above. Source: AWS Center for Quantum Networking.
Remembering light
Quantum repeaters function by transferring data encoded by photons to a stationary qubit, where it is stored and corrected. Qubits with defects, like the color center, can be great options for this procedure due to their efficient connection to the light (the basis of the color) and also because they can access an extended “spin” memory. The spin could be described as a tiny magnet that is located in every proton, electron and neutron in the material. The spin memory is accessible when you place the qubit inside an electromagnetic field so that the spins are oriented to that direction. The memory can then be defined by the spin facing in the opposite direction or along that magnetic field. This translates to the 1 or 0 bits or 0 bit. If light hits an area of color, it could change the spin qubit which allows an exchange between information from light as well as spin memory. This can be called a”spin-photon” interface. Color centers that have this feature such as NV and SiV are excellent potential candidates of quantum repeaters.
Defect qubits are one type of qubits that are created through the introduction of imperfections or defects intentionally into the material to form the quantum bit. They can be controlled and altered to perform quantum-related operations and keep quantum information.
A good example of a defect qubit could be found in that of the nitrogen-vacancy (NV) center of diamond. A nitrogen atom is replaced by carbon atoms in the crystal lattice of diamond, and a carbon atom in the neighboring carbon atom is missing, resulting in the vacancy. The nitrogen and the vacancy create an unreliable defect that can be used as a quantum bit. Qubits with defects have advantages over other kinds of qubits, for example longer coherence time and their ability to function at ambient temperature, which makes them appealing for applications such as quantum information processing and quantum computing.
They NV and SiV differ in comparison to other centers of color because of being housed in diamond it is compatible with spectrum of semiconductor processes. It remains chemically stable and inert in diverse environments. This means that the qubits can be placed inside nanoscale devices that are designed specifically for purposes. For instance, NVs are usually placed near the top of the scanning probe to facilitate microscopy, or in near the middle of a lens , or pillars designed to capture light effectively. SiVs, which are not as sensitive to environmental conditions are able to be placed in smaller structures. They are often used inside photonic crystal cavities and waveguides only 100 nanometers wide.
SiV SiV is part of a well-studied group of defects, referred to by the name of “Group IV” defects due to their position within the periodic table that are distinguished by their insensitivity to electric field and magnetic variations, which are found at the surface of most substances. The reduced sensitivity of SiV makes it possible for SiV to be integrated into smaller structures, which increases the efficiency in their interaction with light. SiV defects are not just light-sensitive. SiV defect is also equipped with additional characteristics that make it designed for quantum networking. SiV has a coherence duration that can be as high as 10 milliseconds and it has a second nuclear spin memory that is able to last longer than 1 second. SiVs are managed and read out with high precision as well as 99.98 percent readout fidelity and one-qubit gate accuracy that is better than 99percent the spin photon gate’s fidelity higher than 95 percent. With Element Six’s artificial diamonds these capabilities have been paired by a group consisting of Harvard and MIT scientists to provide quantum communications that are enhanced by memory which is a test that indicates that the SiV will allow communication that is longer than is feasible without repeaters. The development and expansion of the technology that surrounds the SiV could make widespread adoption of this technology feasibleand the engineering begins with the diamond’s own material.
Synthetic diamond is a artificial diamond created in a lab rather than being naturally formed within the Earth’s crust. Synthetic diamonds are made by advanced technology that mimic the high temperatures and pressure that are found naturally in the mantle of Earth which is where diamonds form. The process typically involves exposing carbon-rich substances to extreme pressures and temperatures similar to those present in the diamond anvil cells.
Synthetic diamonds are used in a broad variety of industrial uses, for example, the cutting and grinding tools in high-precision and precision bearings. They also are used in jewelry that is high-end and are chemically and structurally similar as natural diamonds. But synthetic diamonds are generally less costly than natural diamonds. This makes them a desirable alternative for commercial and industrial applications.
Discovering new solutions to synthetic diamonds for quantum networking
In natural diamonds, the amount of undesired defect atoms decreases the optical, coherence and spin properties of color centers such as the SiV and NV. Thankfully, the development of synthetic diamonds has made removing these undesirable imperfections feasible. The advancements in plasma-enhanced chemical deposition (PECVD) over the past 20 years have led to the creation of diamonds in individual pieces that are of sufficient purity and orderliness for quantum-based applications. PECVD development has allowed the creation of diamonds that are hundreds or thousands of times more pure than the Regent Diamond, the famously pure natural diamond that is on display inside the Louvre. In the most pure PECVD diamond, less than one million atoms is impurities as opposed with one in million for the vast majority of natural diamonds.
Continued investment to invest in PECVD diamond technology is crucial to the development of quantum applications. Improved control over the types of defects that are created and the materials that is incorporated into diamond growth broadening the variety of morphologies of diamonds that can be manufactured in mass quantities, and reducing the cost of manufacturing them is crucial for the development in this area.
An announcement of a new collaboration with AWS Center for Quantum Networking and Element Six
Its quantum and optical qualities make diamond suitable to use quantum networks and communication applications. However, a accessibility to various types of diamond is an obstacle for the field. Element Six and AWS are teaming up to create new techniques to create diamond as a more adaptable and easily accessible material, helping propel growth and advancement for this technology.
This morning, AWS announces a brand new collaboration in research in partnership with Element Six (www.e6.com) to investigate ways to create and enhance synthetic diamonds that can be used for quantum networks.
In the realm of technological advancement and innovation Materials are important.
Synthetic diamond is an enviable solution for quantum communications, in which it can be utilized as a node for the creation quantum network. Diamond memory nodes aid in the growth of the networks through facilitating quantum communications over distances of a long distance – which is a problem that requires quantum memory nodes that are high-quality optical interfaces and lengthy memory times.
Utilizing years of experience
Diamond’s potential in this area was first recognized by groups over 10 years ago, and was also recognized the group Element Six, now an AWS Center for Quantum Networking collaborator.
With more than 70 years of expertise in the field of growth technology development and the application of synthetic diamonds Element Six has pioneered diamond solutions in a variety of challenging areas, such as exploration of oil and gas and water treatment, as well as advanced thermal management of high-performance semiconductor devices, and optical applications for fusion energy and EUV lithography. In collaboration with top academic partners across Europe, the U.S. and Europe, Element Six was the first to demonstrate that synthetic diamond could be manufactured with characteristics that are specifically designed to quantum-related applications. While the field has several technical and fundamental issues and challenges, this cooperation among AWS as well as Element Six aims to develop an scalable synthetic diamond solution that is compatible with a high-quality photon-spin interaction as well as control. It can be utilized to accelerate the advancement of quantum technology that include secure networks, sensors or computers in the near future.
