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Introduction:
In the ever-evolving landscape of quantum technologies, scientists and researchers are delving into the fascinating realm of quantum materials—materials with quirks and peculiar properties that have the potential to transform the fields of quantum computation, communication, sensing, and metrology. These unconventional substances are not just the building blocks; they are the quirky catalysts propelling us into a quantum revolution.
Quantum Revolution
In the 21st century, we are witnessing the dawn of a technological renaissance fueled by quantum-mechanical phenomena. Quantum technology (QT) harnesses the principles of quantum mechanics, such as entanglement, superposition, and the No-cloning theorem, in various quantum systems like atoms, ions, electrons, photons, and molecules. Unlike classical bits, quantum bits (qubits) can exist in numerous states simultaneously, a phenomenon known as superposition.
Quantum entanglement, where particles remain interconnected regardless of distance, and the No-cloning theorem, emphasizing that quantum information cannot be duplicated, are the cornerstones of this transformative technology. The potential applications of QT are vast, spanning computing, sensing, cryptography, and more. Quantum computers, leveraging the unique properties of qubits, hold the promise of surpassing the computational power of today’s supercomputers. Quantum sensors, with capabilities far exceeding current technologies, could revolutionize fields from medicine to seismology. Quantum cryptography, based on the unbreakable link between entangled particles, may redefine secure communication.
Quirky Quantum Materials
Despite the immense potential, challenges loom on the path to fully harnessing quantum technologies. Quantum states are exceptionally fragile, susceptible to the slightest disturbances. Additionally, understanding the intricate correlations between particles in quantum systems remains a scientific puzzle. Overcoming these challenges requires the development of novel materials and structures where quantum effects play a pivotal role.
In response to these challenges, researchers are turning to the realm of quantum materials, a term encompassing materials with unconventional properties that defy classical physics. “Quantum materials” was a phrase originally invented by researchers in condensed matter physics. It’s an umbrella term referring to materials that have properties that cannot be easily described by classical, or low-level, quantum physics. Nowadays people generalize quantum materials to other things, including topological materials, low-dimensional materials, and engineered quantum materials. The ability to manipulate these materials at the nanoscale opens up possibilities for creating innovative quantum devices.
Quantum materials defy conventional physics, demanding a new theoretical language to describe their correlated electron behavior. And scientists still don’t fully understand how to model the complex correlations between particles in quantum systems. Those microscopic correlations are critically important because they ultimately determine the properties of a material at the macroscopic scale. This is driving the development of new materials and structures where such effects play a leading role. The concept of Quantum Materials has become a unifying force across various scientific disciplines, from condensed-matter physics to materials science and quantum computing.
These diverse behaviors all trace to electron interactions. In conventional metals, electrons barely interact with each other: Fermi liquid theory describes their tendency to screen local charge so that electrons can be treated as isolated particles in a homogenous background. In contrast, the common feature to all of these exotic materials is that their electrons do interact, and we lack the broadly successful theoretical language to describe these ‘correlated electron materials.
Typically, the sizes people are working with these days are mostly at the nanoscale or nanometer scale, which is a few billionths of a meter—a scale that’s related to the size of molecules, or a few tens of atoms. To work at this very small scale, special tools and techniques are needed. Specialized tools like electron beam microscopy and lithography become essential in working at this scale, often requiring a clean-room environment.
One of the major challenges in advancing semiconducting technology is that we need to continually decrease the size of nano-electronic components and devices. That leads to new challenges in the quantum limit. For instance, we have issues related to quantum conductance, quantum capacitance, quantum fluctuations as well as increasing heat dissipation. Now, if we incorporate quantum materials, we can actually introduce additional electrical and thermal conduction channels and provide protection barriers and layers to prevent atomic migration in nano devices and nano structures.
The last few decades have witnessed the discovery of materials exhibiting astonishing properties, from high-temperature superconductors to heavy fermion materials.
Quantum materials exhibit a plethora of phenomena such as superconductivity, quantum-Hall effect, quantum spin-Hall, topological-Hall effect, and Dickie’s superradiance. Understanding how we control the manifestation of these properties in materials using knobs such as reduced dimensionality, quantum confinement, quantum coherence, the topology of wavefunctions, quantum fluctuations, electron-electron interactions, and spin-orbit coupling is crucial.
“Quantum materials mean they have properties that cannot be described by classical physics – we have to invoke quantum physics,” said Dr Amalia Coldea, a quantum materials researcher at the University of Oxford. “Often we refer to materials where there are very strong interactions between their components – you don’t know what properties they will have, and you can’t predict in advance.” Quantum materials have various quirky properties, some of which could contribute to future technological innovations like quantum computing – regarded by many as the next revolution in computer technology.
Recent Quantum Materials breakthroughs
The last few decades have seen the discovery of materials with exotic properties few would have imagined. Superconductors exhibit zero resistivity up to 135 Kelvin. Multi-ferroic materials allow a magnetic field to write electric domains and an electric field to write magnetic domains. Colossal magnetoresistance materials change their electrical conductivity by orders of magnitude upon application of a magnetic field. Heavy fermion materials host electrons which behave thousands of times heavier than their actual mass, whereas the electrons in graphene behave as if they were massless. Existing materials display fractional charges in two dimensions, and the recently discovered topological insulators may extend these fractional charges into three dimensions.
- Superconductors: These materials conduct electricity with zero resistance, defying the laws of classical physics. Imagine trains levitating on magnetic tracks or lossless transmission of data across continents – superconductors make it possible.
- Topological insulators: These materials act like insulators on the inside but conductors on the surface, leading to exotic phenomena like one-way electrical currents and the potential for unbreakable quantum bits (qubits) for super-secure quantum computers.
- Weyl semimetals: Imagine particles zipping around like points with no mass, behaving as both fermions and bosons. These mind-bending materials could lead to novel forms of electronics and ultra-sensitive sensors.
In a collaborative effort led by DARPA, Applied Materials, Arm, and Symetrix are spearheading research on correlated electron materials for neuromorphic switches in artificial intelligence (AI). These switches aim to integrate signal transmission and self-learning processes simultaneously, mimicking the synapse’s functionality. DARPA’s project explores correlated electron switches, breaking classical band theory rules.
Applied Materials focuses on purely electronic phase transitions, potentially achieving unprecedented switching speeds, improved reliability, and operation at sub-1K temperatures. Arm contributes circuit designs for low-power chip disruption at the edge.
Meanwhile, a UCF physicist, Madhab Neupane, discovers Hf2Te2P, a quantum material with multiple electron patterns, suggesting profound implications for quantum computing and energy-efficient electronics. Additionally, an international team unveils a new material, Weyl-Kondo semimetal, belonging to quantum materials, presenting diverse properties seen in various substances.
Applications
All of these can lead to devices with better operation efficiency, faster speed, and lower energy consumption for smaller and smaller volumes. That’s becoming an important challenge, at least for nano-electronic applications. Of course, there are many other areas of applications. Quantum materials are not only useful for quantum technology but also for a wide range of applications, such as metrology, sustainability, biomedical and environmental applications, communications, and consumer products.
Quantum Computation: Superposition and Entanglement Dance
Currently, Quantum qubits are mostly made of superconductors, but they’re very low-temperature superconductors. There are many issues with that. They only operate at very, very low temperatures. That makes these qubits not very scalable. If we can advance interesting and good properties of higher-temperature superconductors, then it can certainly help the development of qubits.
Also, there are qubits already made of quantum materials. For example, people have used semiconductor quantum dots and cooled atoms as qubits. So, these are examples of real quantum materials already being used as qubits. And of course, qubits are directly related to quantum computation, explains Nai-Chang Yeh, Caltech’s Thomas W. Hogan Professor of Physics
Quantum materials with properties like superconductivity and topological insulators provide the stable environment necessary for qubits to maintain their delicate superposition states.
Communication Breakthroughs: Quantum Entanglement Across Space
Imagine particles entangled in such a way that the state of one instantly influences the state of the other, regardless of the distance separating them. This is the marvel of quantum entanglement, and quantum materials are taking center stage in this communication breakthrough. Researchers are exploring materials that can maintain entanglement over longer distances, laying the foundation for ultra-secure quantum communication networks. The quirky properties of these materials are unlocking the door to quantum teleportation and uncrackable quantum cryptography.
Sensing the Unseen: Quantum Sensors in Action
Quantum materials are not just performers in the quantum orchestra; they are also the stage on which quantum sensors showcase their prowess. Materials exhibiting quantum properties like superposition and coherence are enabling the development of ultra-sensitive sensors. Quantum sensors can detect minute changes in physical quantities, opening avenues for precise measurements in fields like healthcare, environmental monitoring, and even gravitational wave detection. Quantum materials are the magic wands empowering these sensors to perceive the unseen.
Metrology Marvels: Redefining Measurement Standards
In the world of metrology, precision is key. Quantum materials are redefining measurement standards by providing the stability and accuracy required for cutting-edge quantum metrology devices. From atomic clocks with unparalleled accuracy to magnetic field sensors operating at quantum limits, these quirky materials are elevating our ability to measure fundamental constants and physical parameters with unprecedented precision.
Advances in Quantum materials
These quirky behaviors arise only at very cold temperatures, where they cannot be masked by the overwhelming forces of thermal energy. The most celebrated quantum materials are the high-temperature superconductors discovered in the 1980s, so named for their ability to conduct electrical current without resistance at temperatures well above those of traditional superconductors. Another classic example is the heavy fermion materials discovered in the late 1970s. In these, electrons appear to be effectively hundreds of times more massive than normal and, equally unusual, the effective electron mass seems to vary strongly as temperature changes.
Originally introduced to emphasize the exotic properties of unconventional superconductors, heavy-fermion systems, and multifunctional oxides, the definition of quantum materials has morphed into a much broader container that also encompasses research on topological properties, two-dimensional (2D) materials, and driven quantum systems. This convergence of diverse research areas is perhaps best exemplified by the coexistence of strong correlation, quantum criticality, and superconductivity in Moiré materials such as twisted bilayer graphene (TBG). With this example in mind, it is natural to broadly define quantum materials as all those versatile materials platforms that allow us to explore emergent quantum phenomena as well as their potential uses in future technology.
Recent breakthroughs, such as the discovery of Hf2Te2P, a material with multiple quantum properties, exemplify the ongoing exploration of quantum materials. Researchers anticipate that a deeper understanding of these materials will pave the way for technological innovations comparable to the impact of electronics in the 20th century.
Quantum materials are not confined to the realm of theoretical research; they are actively shaping the landscape of technology. Quantum dots, cooled atoms, and other quantum materials are already being used as qubits for quantum computation. Initiatives like the DARPA-funded research on correlated electron switches and the collaboration between Intel, Berkeley, and Symetrix highlight the practical applications of quantum materials in developing energy-efficient memory and logic devices.
Excitingly, quantum computers are not just tools for studying quantum phenomena but can be programmed to emulate quantum materials. The recent feat of turning IBM’s quantum computer into an exciton condensate showcases the potential synergy between quantum computers and quantum materials.
Europium Molecular Crystals
In March 2022, a research team comprising scientists from the National Centre for Scientific Research (CNRS), the University of Strasbourg, Chimie ParisTech-PSL, and the Karlsruhe Institute of Technology (KIT) reported groundbreaking findings on Europium molecular crystals. Europium molecular crystals, a rare-earth-based material, demonstrated remarkable quantum capabilities, making them a promising platform for photonic quantum technologies.
Rare-earth ions, known for their ability to exhibit long-lived quantum states, are considered suitable for building solid-state systems for light-matter interfaces at the quantum level. However, finding crystalline materials with a sufficiently quiet environment to fully exploit the quantum properties of rare-earth ions has been a challenge. Molecular systems, while providing such an environment, often lack the necessary spin states or exhibit broad optical lines.
Europium molecular crystals, a unique combination of rare-earth ions and molecular systems, showcased ultranarrow linewidths in the tens of kilohertz range—orders of magnitude narrower than other molecular systems. The research team leveraged this property to demonstrate efficient optical spin initialization, coherent storage of light using an atomic frequency comb, and optical control of ion-ion interactions for implementing quantum gates.
The ultranarrow linewidths of Europium molecular crystals allowed for the creation of a long-lasting quantum state, enabling the storage of a light pulse inside the crystals. The researchers believe that these findings highlight the potential of Europium molecular crystals to serve as a robust platform for photonic quantum technologies. The combination of highly coherent emitters and the versatile capabilities of molecular materials in composition, structure, and integration positions Europium molecular crystals as a promising candidate in the development of quantum computers that can communicate using fiber optic networks.
Recent Breakthroughs
1. Ultrafast Superconductivity: Scientists have coaxed a material – lanthanum hydride superconductor – to conduct electricity with zero resistance at a balmy -23°C (significantly higher than usual!). This opens doors for room-temperature superconductors, revolutionizing everything from maglev trains to power grids.
2. Twisted Magic Angle Graphene: Layers of graphene stacked at a “magic angle” – a precise twist of 1.1 degrees – unleash a symphony of exotic phenomena. Electrons dance in a synchronized ballet, exhibiting superconductivity, magnetism, and even light-manipulating properties, offering a playground for next-generation electronics and quantum devices.
3. Quantum Time Crystals: These mind-bending materials defy the very concept of time. Their atoms perpetually rotate in a repeating pattern, even without any external energy source, challenging our understanding of thermodynamics and potentially paving the way for ultra-precise clocks and sensors.
4. Programmable Quantum Metamaterials: Imagine materials whose properties can be dialed up or down like radio knobs. Scientists have built just that, using lasers to manipulate the arrangement of atoms in certain materials, granting them the ability to control light, magnetism, and other properties on demand. This unlocks a treasure trove of possibilities for future optical devices and quantum technologies.
5. Molecular Qubits: Forget silicon chips, the future of quantum computing might lie in tailor-made molecules. Researchers have crafted complex molecules that behave like qubits, the building blocks of quantum computers. These “molecular qubits” offer unique advantages like fault tolerance and scalability, potentially leading to super-powerful quantum machines.
Physicists Say Magnets Offer Room Temperature Quantum Computing
Scientists at The University of Texas at El Paso (UTEP), led by Associate Professor Ahmed El-Gendy, have achieved a groundbreaking development in quantum computing technology by creating a material that operates at room temperature. Unlike conventional quantum computers that require extremely low temperatures just above absolute zero, this newly developed material, a blend of aminoferrocene and graphene, maintains its quantum properties at standard room temperature.
The breakthrough material exhibits magnetic properties that are 100 times stronger than pure iron, eliminating the need for rare Earth materials in magnet construction. This addresses concerns about potential shortages of critical materials in the future. The team’s ambitious goal was not only to enable room temperature quantum computing but also to create a magnet without relying on rare Earth materials.
Currently, most magnets, including those used in smartphones, vehicles, and data storage devices, are made from rare Earth materials. The scarcity of these materials poses a significant challenge for various industries. The UTEP team’s solution, the combination of aminoferrocene and graphene, demonstrated unexpected and remarkable magnetic properties, surpassing the skepticism of even El-Gendy.
The potential impact of this development is vast, as room temperature quantum computers could revolutionize various sectors, including health and science. The breakthrough material could pave the way for cost-effective quantum computing without the need for expensive cooling systems. The success of this research not only represents a significant advancement in quantum computing but also offers a potential solution to material shortages, marking a crucial step forward in the field.
These are just a few glimpses into the thrilling world of cutting-edge quantum materials research. With each breakthrough, the boundaries of physics are pushed further, bringing us closer to a future where materials with superpowers become our reality.
Using AI/ML for searching and designing new Quantum Materials
In addition to experimental advancements, the utilization of artificial intelligence and machine learning (AI/ML) techniques is gaining prominence in the search and design of new quantum materials. The growing library of quantum materials necessitates efficient cataloging, searching, and design strategies, and ML algorithms are crucial in handling the massive amount of data generated in computational materials science. ML is expected to play a central role in identifying patterns, extracting knowledge, and advancing the understanding of quantum phase transitions and many-body physics, contributing to the development of next-generation quantum technologies.
Conclusion: Riding the Quantum Wave
As we stand on the cusp of the Quantum Age, the exploration of quantum materials is becoming synonymous with unlocking the mysteries of the quantum frontier and ushering in a new era of technological marvels. Their quirky properties are not mere oddities but the secret sauce that fuels quantum advancements. From enabling quantum computers to communicate effortlessly across vast distances to sensing the subtlest changes in our surroundings, these materials are the trailblazers in the quantum frontier. So, buckle up and get ready for a quantum leap into a future where the extraordinary becomes the new ordinary, all thanks to the quirky wonders of quantum materials.
References and Resources also include:
https://news.uchicago.edu/story/uchicago-scientists-turn-ibm-computer-quantum-material
https://www.photonics.com/Articles/Europium_Molecular_Crystals_Clear_a_Path_for/a67883
