ARCHIV

2021

30th of Sep. 2021

Ronald Hanson and colleagues present in an interesting review article (see: J. Appl. Phys. 130, 070901 (2021); doi: 10.1063/5.0056534) a summary on quantum networks based on diamond color centers. They identify that diamond color centers already define the state of the art in multi-node entanglement-based networks and in memory-enhanced quantum key distribution. They expect a rapid progress on photonic interfaces and integration of color centers, which will initiate long-distance quantum links which will stimulate new applications like distributed quantum computing. The authors indicate that color centers in diamond may play an essential role in these networks.

Schematic overview of a future large-scale quantum network, consisting of nodes containing optically interfaced qubits (purple) with long coherence times. Photons routed via optical fibers or free-space channels serve as mediators to create entanglement (blue wiggled lines). Local area and trunk backbone quantum repeaters (dark and light red circles, respectively) are used to enable a high entanglement generation rate over large distances, overcoming photon transmission loss. The entangle-ment generation is heralded, meaning that detection of certain photon statistics signals the successful generation of an entangled state that is available to a network user for further processing and applications such as networked quantum computation, quantum secured communication, quantum enhanced sensing, and potential not yet dis-covered tasks.

12th of Aug. 2021

Diamonds are known to be among the stiffest materials known to man. A new study finds a worthy competitor to the naturally-occurring cubic diamonds - in the form of lab-made hexagonal diamonds.

In a Phys. Rev B. paper (Elastic moduli of hexagonal diamond and cubic diamond formed under shock compression, Travis J. Volz and Y. M. Gupta, Phys. Rev. B 103, L100101) the relative stiffnesses and strengths of hexagonal diamond and cubic diamond have been characterized by use of laser interferometry to determine the longitudinal sound speeds and moduli in hexagonal diamond and cubic diamond formed during the shock compression of graphite. The hexagonal diamond longitudinal moduli are significantly larger than the cubic diamond longitudinal moduli, and even exceed averaged cubic diamond single crystal values. The measured hexagonal diamond longitudinal moduli, combined with high-pressure bulk moduli for cubic diamond single crystals, show that shock-formed hexagonal diamond shear moduli are larger than the shear moduli for cubic diamond single crystals (image below from: https://taylorandhart.com/ie/diamond-guidance/diamond-shapes/hexagon).

9th of August, 2021

Electronics is all over, increasingly dominating our business as well a private life. The "trillion sensor" reality has already approached making houses, cars, offices and factories intelligent and connected. Faster communication networks and more powerful quantum computers are coming. Electronic power grids become smart as well as dynamic energy storage technology for E-mobility and delocalized energy generation facilities. Here, super capacitors in combination with conventional batteries are currently developed and optimized.

All these new approaches cannot build on Si-technologies which have been developed and optimized since the middle of last century. Although, silicon-based devices are still useful for a variety of applications, they are not at all “best solutions” for the challenges of our times. A paradigm change in electronics has started. Semiconductors of the future need to be environmentally sound, sustainable, available all over, as well as cheap and easy to recycle. New semiconductor devices will be hetero-integrated 3D architectures which can be miniaturization towards the atomic limit to utilize low dimensional electronic properties based on charges and spins. Quantum technologies which cover sensing, communication, imaging and computing will be applied. In bio-medical medical applications chemical inertness, biocompatibility and functionality are very high on the wish list. Altogether, these demands are terminating the “silicon age”.

The search for new materials which better suit demands than silicon has started already years ago. New materials are targeting properties which can manage a) terahertz electronics, b) quantum sensors and emitters, c) emission of entangled photons, single photons, d) spin entanglement (Q-bits), e) spintronics and d) surface enlarged energy storage devices, to name a few. The rich list of possible materials, however, is reduced significantly if we take into account environmental requirements or sustainability. The European Union Regulation “REACH” (Registration, Evaluation, Authorisation and Restriction of Chemicals) [1] clearly identifies elements which should be used in the future. If we take into account the required properties mentioned above for applications, carbon-based materials are the winners.

Carbon forms a vast number of compounds, dominates the organic chemistry and is the basis of all known life on earth. It forms several allotropes of which best known are a) graphite, b) diamond, c) carbon nanotubes (CNT), d) graphene and e) fullerenes. The properties of these allotropes vary significantly, offering numerous unique features which will dominate an increasing number of future technologies. They span a range of extremes from a) hardest materials known ("diamond") to b) softest materials ("graphite"), c) best thermal conductor (diamond) to d) chemical inertness and e) biocompatibility (graphene, diamond), to mention only a few. Carbon based materials can be fabricated as fiber, sheets, foam, particles, and tubes raging from macroscopic dimensions down to the nanoscale. Especially nano-scale carbon materials like expanded graphite and graphene are currently developed for applications like super-capacitors where large surface enlargements in combination with durability and chemical stability are important. The production of these allotropes covers numerous methods and are entering high technology readiness Ievels to be implemented in mass production for markets like airplanes and cars (carbon fibers), in electronics (diamond and graphene) and energy storage devices like super-capacitors (expanded graphite, graphene) as well as in power grits (diamond power-electronics).

The resources of carbon in nature are “unlimited”. The basic chemistries for transformation into sp2 and sp3 bonded structures are well established. Major ingredients for chemical vapor deposition (CVD) of diamond and graphene are methane and hydrogen, both gases are cheap and available without limits. Methane is a greenhouse gas like CO₂ with a comparative impact which is 25 times greater than CO₂. The use of methane from the atmosphere (which is available all over the globe) for the deposition of diamond layers will therefore be environmentally sound. Furthermore, methane can be generated from chemical reduction of CO₂ (again available in the atmosphere) in combination with renewable energy (wind, solar), so that both CO₂- and CH₄-contamination of the atmosphere can be reduced to approach the carbon neutral or negative technologies. Furthermore, CO₂ and CH₄ are available in our atmosphere so that these technologies can be applied all over the world without expensive transportation as both resources. The formation of sp3 and sp2 carbon is simple chemistry which require no catalyst if proper techniques are selected and applied. The extra amount of energy required for the reduction of CO₂ can be generated by renewable technologies like wind energy. A technology which is available and already in use. Oxidation of carbon (sp3 and sp2) will form CO₂ again, so that a closed carbon recycling circle is available. The new carbon-based electronic age will be a closed system, which is sustainable as well as environmentally sound, utilizing the best electronic, optical, mechanical as well as quantum-related properties available in nature. However, fast progress in research and development of carbon-based devices is required to achieve these goals in time. 

Literature:

1. Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency. OJEC L396, 30.12.2006, pp. 1–849.

14th of March 2021

Neuer Text

11th March 2021

In a recent paper (see: arXiv:2103.03784) Savvin and co workers showed lasing in diamond samples doped with nitrogen vacancies (NV) negatively charged color centers. The NV centers are promising as lasing medium as NV shows large emission and absorption cross sections, high quantum efficiency and a broad gain band. They are therefore suitable for tunable and femtosecond lasers in the red and near infrared. Unfortunately, the presence of neutrally charge NV centers lead to a decrease of the stimulated emission. Nonetheless, stable lasing at a 720 nm with a width of 20 nm, 1 ns duration and total energy around 10 nJ was achieved. This will stimulate diamond based laser applications which can build on unique properties like highest thermal conductivity, low thermal expansion, high optical transparency, which makes diamond an excellent candidate for high-power CW and ultrashort laser applications.

6th March 2021

Quantum networks require nodes that emit indistinguishable photons. Solid state single photon emitters (NV, SiV, SnV etc.) are candidates, however, as they are embedded in individual strain fields, the emission of each center is slightly different.
To achieve indistinguishable emission, precise tuning of optical transition frequencies is essential and has been demonstrated now by S. Aghaeimeibodi et al. (see: arXiv:2103.01917v1, 2nd Mar. 2021.) using the SnV center in diamond and electric field (Stark effect) tuning. The team characterized the emission frequency of the SnV-center tuned by externally applied electric fields and show a shift of more than 1.7 GHz without introducing a significant broadening of the transition linewidth. They successfully demonstrated that Stark tuning can be used to tune the optical frequency of single photon sources and thereby to control the degree of indistinguishability. These results pave the way for multi-emitter experiments based on group-IV color centers in diamond using the Stark shift tuning for applications in quantum cryptography communication lines.

27th Feb. 2021

Zhang (D. Budker team) report ind a recent ArXive article about sensitive and accurate diagnostics, using the NV in diamond for magnetic sensing to identifying and localize defects in rechargeable solid batteries. They demonstrate AC magnetometry, distinguish a defect on the external electrode and identify structural anomalies within the battery body. The achieved spatial resolution is 360 micro-meter and the magnetic sensitivity is 40nT/(Hz)^0.5.

The propose an improvement of the spatial resolution by either using thinner diamond samples or diamonds with shallower implanted NV layers to shorten the sensor-sample distance. By tuning the bandwidth, it would be possible to identify structures, at different depth inside the battery including electrodes, electrolytes and even material components, which could be useful for battery assessment and development.

21st Feb 2021

Washington diamond (WD) Lab Grown Diamonds and the Carnegie Institute of Washington have settled their legal battle with Pure Grown Diamonds and IIa Technologies over lab-grown diamond patents in November 2020.

WD and Carnegie’s legal challenge centred on the alleged breach of two patents 6,858,078 and RE41189. The 078 patent licenced in 2011 to WD describes a method for producing CVD diamonds using a microwave-plasma process and RE41189 outlines a method for improving a diamond’s visual qualities using high-pressure, high-temperature treatment, and can be used on natural diamonds as well.

In a joint motion filed to the US District Court for the Southern District of New York, lawyers for both parties announced they had settled their case with no stipulated conditions.

Pure Grown Diamonds and IIa Technologies had previously attempted to have the case dismissed on the grounds that diamond growth is a natural phenomenon and therefore cannot be patented.

14th Feb 2021

S. Pezzagna and J. Meijer summarize in a very exciting new publication the potential of color centers in diamond to be used for quantum computer core processors. Their discussion is based on results achieved over recent years, which clearly indicate that color centers in diamond are suitable for spin manipulation, processing and storage, requirements which are at the heart of solid state quantum computing. They argue that deterministic single-ion implantation has been developed to a level, which in combination with thermal treatments leads to the produce NV centers in diamond with high yields. Besides optical addressing, also electrical read out of single NV centers by means of the photocurrents has been reported. In addition, NV centers can be interlaced with many 13C nuclei. Altogether findings which represent a game-changer for the application of NV centers in quantum computing core processors.

Pezzagna and Meijer conclude that next steps should target the building of quantum computing systems using the magnetic dipole–dipole coupling of NVs, where each NV center is connected to several 13C qubits close to the surface of diamond. The NV centers should be electrically readout and controlled by microwave pulses which can be implemented by crossed nanowires above each NV. They suggest the coupling of 100 NV qubits within a 10 × 10 grid. This will provide a 1000 qubit system because each NV-center can further control up to ten 13C qubits. The coupling can be modified using photons, free electrons, phonons or others techniques. These concept of Pezzagna and Meijer are exciting. The realization appears reasonable but will required significant improvements in spin-manipulation technologies, spin storage and transfer. This will open-up a new chapter of diamond in quantum technology – expanding beyond quantum sensing.

29th Jan. 2021

Hueray Microwave Technology (http://www.hueray.cn/en) announced a solid-state microwave plasma discharge system for the deposition of diamond.

The system uses a newly developed 6kW/2.45 GHz solid-state microwave power generator. The microwave power is continuously adjustable from 0.1-6kW; the stability is better than 1%; the ripple is better than 1%, and it has good control performance, Hueray proposes excellent electrical performance, safe and reliable, simple and convenient operation.

20th Jan. 2021

The French President has just announced that the french research centers, start-ups and industrial groups will have a budget of 1.8 billion euros over five years. France has now a Quantum Plan.

The French Quantum Plan will focus on research aimed to quantum computers but also to develop quantum sensors and secure quantum communications.

With renowned physicists (Alain Aspect, Serge Haroche), major companies (Atos and Thales for the design of quantum technologies; EDF, Total and Orano for their use) and start-ups, France already has a world-class quantum ecosystem. But the underfunding of its research has always been a serious drawback, which pushes many researchers to emigrate.

In this context of strong international competition, most of the funding of this Quantum Plan will therefore be granted to research and academics.

Of the 1.8 billion, 350 million will go to the development of quantum simulators (Atos!) and 430 million to the quantum computers.

1st Jan 2021

Diamond is a wide-bandgap semiconductor with most promising properties for quantum-technology, optical and electronic applications. In addition, due to its extreme hardness micro- and nano-electro-mechanical-systems (N/MEMS) from diamond work at highest frequencies with unmatched properties for 5G or higher communication systems or sensing applications in nano-mechanical and nano-opto-mechanical devices.

It is well known in semiconductor physics that strain if large enough can be used to vary the band-gap of materials, giving rise to an insulator-metal transition. Now, a joint research team led by City University of Hong Kong (CityU) has demonstrated for the first time that large, uniform tensile elastic strain of microfabricated diamond arrays can fundamentally change the bulk band structures of diamond, including a substantial calculated bandgap reduction as much as ~2 electron volts. This will effect especially future applications of diamond in photonic nanostructures and N/MEMS where this discovered phenomenon can be utilized for new or improved sensing. It will also help to understand the electronic properties of strained regions of diamond located for example at defects like dislocations better.

This result support recently published data from Shi et al. (“Metallization of diamond” by Zhe Shi, Ming Dao, Evgenii Tsymbalov, Alexander Shapeev, Ju Li, Subra Suresh, PNAS, October 6, 2020, vol. 117, no. 40, pp. 24634–24639). They showed through first-principles calculations and finite-element simulations that metallization/demetallization as well as indirect-to-direct bandgap transitions can be achieved reversibly in diamond under strain. 

Source: "Matallization of diamond" by Zhe Shi, Ming Dao, Evgenii Tsymbalov, Alxander Shapeev, Ju li, Subra Suresh, PNAS, October6, 2020, vol. 117, no.40, pp. 24634-24639

2020

21 Dec 2020

Ryan Shearman and Dan Wojno, founders of Aether (https://aetherdiamonds.com) invented a new and exciting technique to produce diamond gems quite different to natural stones. Natural diamonds are fabricated by mining: an energy-intensive process of carving gems from the earth, typically involving heavy machinery and explosives, unreliable certifications, with forced or unfair labor.

The CVD process of Aether essentially goes like this: CO2 is scrubbed from the air using direct capture technology; it is pushed through a filter and converted into methane, the raw hydrocarbon material that will eventually become a diamond; and it’s placed in a reactor, where it will grow into a stone. The entire process takes three to four weeks, typical for CVD diamond, then the raw diamond is ready for refinements to become a gemstone. Aether claims, that each carat removes approximately 20 tons of carbon out of the sky—a number that’s higher than the average American’s carbon footprint per year.

Source: https://aetherdiamonds.com/

22nd Dec. 2020

Super-fast quantum computers and communication devices could revolutionize countless aspects of our lives — but first, researchers need a fast, efficient source of the entangled pairs of photons such systems use to transmit and manipulate information. Researchers at Stevens Institute of Technology have now done just that, creating a chip-based photon source 100 times more efficient than previously possible. The work brings massive quantum device integration within reach.

To create photon pairs, researchers trap light in carefully sculpted nanoscale microcavities; as light circulates in the cavity, its photons resonate and split into entangled pairs. At present, such systems are extremely inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end. Huang and colleagues at Stevens have now developed a new chip-based photon source that’s 100 times more efficient than any previous device, allowing the creation of tens of millions of entangled photon pairs per second from a single microwatt-powered laser beam.

Source: "https://scitechdaily.com/entangled-photons-created-100-times-more-efficiently-than-previously-possible/

15th Dec 2020

A joint international research team from POSTECH of South Korea, Raytheon BBN Technologies, Harvard University, and Massachusetts Institute of Technology in the U.S., Barcelona Institute of Science and Technology in Spain, and the National Institute for Materials Science in Japan have together developed ultrasensitive sensors that can detect microwaves with the highest theoretically possible sensitivity. The research team innovated the aspect of materials and structure of the sensor device. Firstly, the team used graphene as the material for absorbing electromagnetic waves. Graphene is made up of one layer of carbon atoms and has a very small electronic heat capacity. The small heat capacity signifies that even if little energy is absorbed, it causes a big temperature change. Microwave photons have very little energy, but if absorbed by graphene, they can cause considerable temperature rise. The problem is that the temperature increase in graphene cools down very quickly, making it difficult to measure the change. To solve this problem, the research team adopted a device called the Josephson junction. This quantum device, composed of superconductor-graphene-superconductor (SGS), can detect temperature changes within 10 picoseconds via an electrical process. This makes it possible to detect the temperature changes in graphene and the resulting electrical resistance.

Combining these key ingredients, researchers reached the noise equivalent power of 1 aW/Hz1/2, which means the device can resolve 1 aW (1 trillionth of a watt) within a second.

11th Dec. 2020

On the electromagnetic spectrum, terahertz light is located between infrared radiation and microwaves. It holds enormous potential for tomorrow’s technologies: Among other things, it might succeed 5G by enabling extremely fast mobile communications connections and wireless networks. The bottleneck in the transition from gigahertz to terahertz frequencies has been caused by insufficiently efficient sources and converters. Now, a German-Spanish research team with the participation of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now developed a material system to generate terahertz pulses much more effectively than before. It is based on graphene, i.e., a super-thin carbon sheet, coated with a metallic lamellar structure.

Source: "https://scitechdaily.com/new-material-system-developed-to-convert-and-generate-terahertz-waves-for-tomorrows-technologies/

2018

2018

Fundamental research has shown that carbon nano-membranes (CNMs) have record high permeance for water while blocking nearly everything else like salt, small organic molecules and nanoparticles with exception of helium.
Combined with a high intrinsic pore density (other than for further membranes using collective transport like aquaporin (AQP)-, porous graphene (PG)-, graphene oxide (GO)-, or carbon nanotube (CNT)-based membranes), this allows to develop radically new separationtechnologies.

Source: Carbon Nanomembranes

 A. Turchanin, A. Gölzhäuser, Adv.Mater. 2016,28, 6075-6103