Category Archives: Quantum Physics
What Is a Quantum Battery? And When Will It Power My Laptop? – Gizmodo
The modern battery has come a long way in its 224-year history. In the place of Alessandro Voltas piles of metal disks and brine-soaked cloth, we now have batteries the dimensions of a graham cracker that can last days before needing a recharge.
But what is the ceiling of the devices currently on the market? What sort of technical challenges must be overcome to break that ceiling, and when will such hurdles be cleared? What is the future of energy storage?
A handful of scientists around the world are working on an answer: a battery technology that uses the laws of quantum physics, rather than classical physics, to hold a charge. Its a long, long way out, but Rome wasnt built in a dayand it certainly wasnt powered in one.
A battery is a piece of technology that uses chemical reactions to produce electrical energy. Household batteries produce electrical energy via the flow of electrons through a circuit. Different battery cells have been developed over the centuries; Benjamin Franklin is considered to have coined the term electrical battery in a 1749 letter, which he concluded with an amusing riff on the marvels of electricity:
A Turky is to be killed for our Dinners by the Electrical Shock; and roasted by the electrical Jack, before a Fire kindled by the Electrified Bottle; when the Healths of all the Famous Electricians in England, France and Germany, are to be drank in Electrified Bumpers, under the Discharge of Guns from the Electrical Battery.
Fast forward through a few different battery cells, mostly named for the scientists who developed them using chemical reactions of various acids and metals, and in 1859 we got the lead-acid batterythe first with the capacity to recharge by reversing current through the system. In the late 20th century, the lithium-ion battery became in vogue and has basically remained popular since, using different permutations of lithium combined with other metals and phosphates. But throughout the modern batterys history, the basic principle of a chemical reaction begetting electrical power has not changed.
Lets quickly review quantum physics in broad strokes. Particles in quantum states operate under an entirely different set of rules from everything you see around you, from the water in clouds to the blood vessels coursing through your veins. Particles enter quantum states under extreme conditions: very cold temperatures and in vacuums. In these conditions, particles can act like multiple things at once, making them useful for doing things like complicated mathematical operations (as a quantum computer does) and checking whether time travel (in a sense) is possible.
Quantum systems can also exhibit entanglement, a phenomenon by which two or more quantum particles define the characteristics of each other. In quantum computers, atoms in an array carry the information necessary for the given operation, as bits do in an ordinary computer. These atoms are quantum bits, or qubits.
But quantum operations are delicate. The moment any value in a quantum system is made certain, the operation falls apart. The entire systemfor example, atoms in an arrayis then back in a classical state.
Quantum states can persist for a long time. Take time crystals, a state of matter first proposed in 2012 which earlier this year physicists showed could persist for at least 40 minutes, about 10 million times longer than other known crystals. These crystals are far afield from quantum batteries but showcase how fleeting some quantum systems normally arean important issue to solve if were ever going to rely on such regimes for power.
So how do the rules of quantum mechanics apply to a battery, the technology that allows you to keep reading this article and maybe more thereafter, once you recharge?
Like normal batteries, quantum batteriesas they are imaginedstore energy. But thats where the similarities end. Unlike the chemical reactions that both charge up and expend a batterys stored energy, quantum batteries are powered by quantum entanglement or behaviors that more closely tether the battery and its source.
Quantum batteries are composed of many quantum cells that act like one big quantum battery, said Ju-Yeon Gyhm, a quantum researcher at Seoul National University in South Korea, in an email to Gizmodo. The challenge is how to maintain the quantum properties for a long time.
Since the same properties apply to quantum batteries as quantum computers, a major technical challenge must be cleared to see the technology become a reality outside of research settings: Physicists must figure out how to keep quantum systems in their delicate states outside of the most carefully managed research settings. A room-temperature superconductor would be such a grail, but these days the only folks claiming such a discovery had their work debunked within months.
Thermodynamics at equilibrium does not set bounds on how fast energy is transformed into heat and work, wrote a team of five scientists in a recent colloquium on quantum batteries, currently hosted on the preprint server arXiv. Therefore it seems natural to seek thermodynamic quantum advantages in quantum systems that are driven out of equilibrium.
The group went on to note that quantum entanglement is linked with how fast energy can be stored in many-body quantum systems, a discovery that has prompted research into quantum systems as energy storage devices.
In 2018, a team modeled the Dicke quantum battery, the first proposed to exist in a solid-state architecture, and in 2022, a team tested out a basic framework for a quantum battery in a lab setting using a target, mirrors, and laser light.
Late last year, a team of quantum researchers proposed a system by which quantum batteries could charge in an indefinite causal order, or ICO. Their findingspublished in Physical Review Lettersposited that a charging system with ICO could outperform conventional charging protocols.
Roughly speaking, ICO can be used to construct quantum processes which are not possible in the standard quantum theory, where causal order must be definite, or fixed, said Yuanbo Chen, a researcher at the University of Tokyo and lead author of the research, in an email to Gizmodo. This flexibility allows for a wider variety of quantum processes, some of which can show advantageous and interesting properties.
We saw huge gains in both the energy stored in the system and the thermal efficiency. And somewhat counterintuitively, we discovered the surprising effect of an interaction thats the inverse of what you might expect: A lower-power charger could provide higher energies with greater efficiency than a comparably higher-power charger using the same apparatus, Chen said at the time.
Different experimental setups of quantum battery systemsboth proposed and realizedmean there are different pathways to innovate on the design of such a futuristic technology. Last month, a team from the University of Gdansk and the University of Calgary proposed a quantum battery charging system that maximizes the amount of energy stored in the battery while minimizing the amount of energy that dissipates (or is lost) in the charging process. Part of the teams redesign is that the quantum battery and its charger are coupled to the same reservoir, producing an interference-like pattern which improves the efficiency of energys transfer between the two. The team estimate that the battery can store four times as much energy through the new charging process than using a conventional charger.
Quantum batteries act more like a wave where the molecules or atoms act in unison, whereas in conventional batteries the molecules or atoms act more like individual particles, said James Quach, a quantum researcher at the University of Adelaide in Australia, in an email to Gizmodo. This collective behavior is what underpins the superextensive charging properties of quantum batteries, where it takes less time to charge quantum batteries of larger capacity.
In 2022, a team led by Quach tested out a basic framework of a quantum battery by putting molecular dye called Lumogen-F orange in a small cavity, and pulsed light at it to see how it stored the energy transmitted by the photons of light. The team found that the system charged up remarkably fast, and that larger systems generally ought to charge faster.
Currently it takes femto- to picoseconds to charge a quantum battery that stores about a microjoule of energy for nano- to milliseconds, Quach said. Although this does not sound like a long time, its storage time is actually more than million times longer than its charging time. As a comparison, this would be equivalent to a conventional battery which takes minutes to charge, being able to hold that charge for hundreds of years.
As reported by New Scientist, some physicists theorize that a quantum batterys charge time is inversely proportional to the number of qubits in the system; in other words, the bigger the battery, the faster it charges.
Quantum battery research is gaining traction, but its still very much in its infancy. Though their promise is remarkable, what the ultimate design of the technology will be remains an open question. Commercialization? Thats but a twinkle in the eye of the most business-minded physicist at the moment.
The chief issue remains getting quantum systems to stay in a quantum state when they scale up. Quach believes that quantum batteries could be used as a mobile energy source in phones and cars, but many quantum systems currently need very cold, noiseless conditions to stay that way (as an aside, Quachs 2022 experimental setup operated at room temperature). Not to demoralize you, dear reader, but nuclear fusion is probably closer to reality than quantum batteries in our devices.
Though many a skeptical reporter is loathe to admit it, Id love to eat my words. The only thing better than being right is finding the world a better place at the expense of being wrong. Quantum batteries could charge faster and more efficiently than classical devices, and could integrate with budding quantum technologies that are used for lofty simulations and measurements. A fully operational quantum battery has not yet been demonstrated, but according to the recent colloquium, such a technology could revolutionize the way we harvest, deliver, and control energy. Given humanitys obvious reliance on electricity, energy storage could use a quantum leap.
More:Physicists Got a Quantum Computer to Work by Blasting It With the Fibonacci Sequence
See the original post:
What Is a Quantum Battery? And When Will It Power My Laptop? - Gizmodo
Physicists Discover Innovative Approach to Represent Pi – Mirage News
While investigating how string theory can be used to explain certain physical phenomena, scientists at the Indian Institute of Science (IISc) have stumbled upon on a new series representation for the irrational number pi. It provides an easier way to extract pi from calculations involved in deciphering processes like the quantum scattering of high-energy particles.
The new formula under a certain limit closely reaches the representation of pi suggested by Indian mathematician Sangamagrama Madhava in the 15th century, which was the first ever series for pi recorded in history. The study was carried out by Arnab Saha, a post-doc and Aninda Sinha, Professor at Centre for High Energy Physics (CHEP), and published in Physical Review Letters.
"Our efforts, initially, were never to find a way to look at pi. All we were doing was studying high-energy physics in quantum theory and trying to develop a model with fewer and more accurate parameters to understand how particles interact. We were excited when we got a new way to look at pi," Sinha says.
Sinha's group is interested in string theory the theoretical framework that presumes that all quantum processes in nature simply use different modes of vibrations plucked on a string. Their work focuses on how high energy particles interact with each other such as protons smashing together in the Large Hadron Collider and in what ways we can look at them using as few and as simple factors as possible. This way of representing complex interactions belongs to the category of "optimisation problems." Modelling such processes is not easy because there are several parameters that need to be taken into account for each moving particle its mass, its vibrations, the degrees of freedom available for its movement, and so on.
Saha, who has been working on the optimisation problem, was looking for ways to efficiently represent these particle interactions. To develop an efficient model, he and Sinha decided to club two mathematical tools: the Euler-Beta Function and the Feynman Diagram. Euler-Beta functions are mathematical functions used to solve problems in diverse areas of physics and engineering, including machine learning. The Feynman Diagram is a mathematical representation that explains the energy exchange that happens while two particles interact and scatter.
What the team found was not only an efficient model that could explain particle interaction, but also a series representation of pi.
In mathematics, a series is used to represent a parameter such as pi in its component form. If pi is the "dish" then the series is the "recipe". Pi can be represented as a combination of many numbers of parameters (or ingredients). Finding the correct number and combination of these parameters to reach close to the exact value of pi rapidly has been a challenge. The series that Sinha and Saha have stumbled upon combines specific parameters in such a way that scientists can rapidly arrive at the value of pi, which can then be incorporated in calculations, like those involved in deciphering scattering of high-energy particles.
"Physicists (and mathematicians) have missed this so far since they did not have the right tools, which were only found through work we have been doing with collaborators over the last three years or so," Sinha explains. "In the early 1970s, scientists briefly examined this line of research but quickly abandoned it since it was too complicated."
Although the findings are theoretical at this stage, it is not impossible that they may lead to practical applications in the future. Sinha points to how Paul Dirac worked on the mathematics of the motion and existence of electrons in 1928, but never thought that his findings would later provide clues to the discovery of the positron, and then to the design of Positron Emission Tomography (PET) used to scan the body for diseases and abnormalities. "Doing this kind of work, although it may not see an immediate application in daily life, gives the pure pleasure of doing theory for the sake of doing it," Sinha adds.
Follow this link:
Physicists Discover Innovative Approach to Represent Pi - Mirage News
Quantum education: Are universities gearing up? – Deccan Herald
Driverless cars and robotic surgeries are only diminutive indicators of tomorrows world. Artificial intelligence driven by quantum machine learning will increase automation that will transform life on Earth. Two-thirds of the skills humanity relies on today to make a living would be obsolete. Tomorrows citizens must be schooled in emerging technologies and lifestyles in an environment beyond todays fiction.
A few hundred years ago, the responsibility for general life preparation shifted from parents to universities. A university is the stage where the scene changes; it must rehearse tomorrows citizens to perform on a 3+n-dimensional scaffold. Sustainability, virtualisation of the physical experience, novel sensors, and communication strategies pose unprecedented challenges for university curricula.
Important milestones in developing digital logic include the works of George Boole, Maurice Karnaugh, Claude Shannon, and Alan Turing. This field leapfrogged into the quantum world through the visions of Richard Feynman, Paul Benioff, and David Deutsch over four decades ago. Willfully or unwittingly, (i) Quantum Computing & Simulations, (ii) Quantum Communications, (iii) Quantum Sensing & Metrology, and (iv) Quantum Material & Devices have crawled into our lives. These are the four verticals of the Titanic National Quantum Mission undertaken by the Indian government.
Explaining the unexplained
Even though Newtons laws describe most of the everyday phenomena, they cannot explain all natural phenomena in the physical world, including some involving macroscopic objects. One needs the quantum theory, developed by Planck, Einstein, Schrdinger, Heisenberg, Dirac and others.
Quantum theory is over a hundred years old. Along with its heroes mentioned above, distinguished scholars from Bharat, like Satyendranath Bose, C V Raman, and Meghnad Saha, made outstanding contributions to develop it.
Their works led to developing and understanding semiconductors and lasers, laying the foundations of a societal revolution. However, certain aspects of the quantum principle of superposition, which produce the entanglement of objects, are only beginning to be exploited. It is this developing scenario that is called the quantum sciences and technologies.
An algorithm is a set of rules that produces an output for an input. It performs computations involving decision-making and data processing; essentially, it solves problems of our interest. Current computers are built using quantum devices (such as semiconductors). Still, the calculation algorithm is driven by classical (Boolean) logic, using bits (0 or 1, i.e., a switch that is off or on). Quantum computers employ quantum logic; they use quantum bits or qubits (quantum superpositions of 0 and 1).
Quantum computing employs abstract mathematics but is highly successful in describing nature. It produces exceptional power to implement computations. Quantum computers are, however, not expected to replace classical algorithms. They will nonetheless be able to outperform classical machines unimaginably, addressing the mounting demands of our changing world.
The earliest schemes that used qubits are the Deutsch-Jozsa algorithm (1992), Shors factorisation scheme (1994), Simons algorithm (1994), and Grovers search algorithm (1996). Now, quantum computational schemes have advanced to address extremely complex problems.
Wide-ranging applications
The quantum future began a century ago, but the present is incubating unprecedented technology driven by quantum entanglement, which gives us a new sense of the physical reality. Wide-ranging applications include the development of efficient algorithms for drug discovery, indissoluble encryptions for information and wealth management, secure communication, the development of ultrafast sensors and metrology that would trigger a rapid response to unforeseen adversities, etc. Encryption standards would be revolutionised under Post-Quantum-Cryptography (PQC), though challenges remain in developing practical protocols.
Artificial intelligence and machine learning are already pushing technologies; the AI-ML tools would be supercharged when driven by quantum entanglement. Only a few quantum computers are available today, but there will be thousands in another decade!
The changes in technology these computers will produce in the coming decade will surpass the number of those produced in the past hundred years. Quantum algorithms will drive supply chain, travel, healthcare, financial services, entertainment and media, information processing, buildings and infrastructure, telecommunication and networks, determining optimum routes amid multiple nodes in a complex environment, and whatnot!
Emerging quantum technologies are intrinsically interdisciplinary. Expertise in mathematics, physics, and all specialised engineering domains will continue to be needed, but in increasingly novel ways. Universities must reinvent the curricula since tomorrows workers will use different tools and extraordinary ideas. Education has to begin with familiar and intuitive ideas, but it must gently and swiftly ramp up todays students to be prepared for tomorrow before it becomes yesterday.
(The author is a professor at the School of Computer Science and Engineering at a university in Bengaluru)
Published 17 June 2024, 20:21 IST
See the original post:
Quantum education: Are universities gearing up? - Deccan Herald
Quantum Magic: How Super Photons Are Shaping the Future of Physics – SciTechDaily
Artists view of a photonic Bose-Einstein condensate (yellow) in a bath of dye molecules (red) that has been perturbated by an external light source (white flash). Credit: A. Erglis/Albert-Ludwigs University of Freiburg
Researchers at the University of Bonn have demonstrated that super photons, or photon Bose-Einstein condensates, conform to fundamental physics theorems, enabling insights into properties that are often difficult to observe.
Under suitable conditions, thousands of particles of light can merge into a type of super photon. Physicists call such a state a photon Bose-Einstein condensate. Researchers at the University of Bonn have now shown that this exotic quantum state obeys a fundamental theorem of physics. This finding now allows one to measure properties of photon Bose-Einstein condensates which are usually difficult to access. The study was published on June 3 in the journal Nature Communications.
If many atoms are cooled to a very low temperature confined in a small volume, they can become indistinguishable and behave like a single super particle. Physicists also call this a Bose-Einstein condensate or quantum gas. Photons condense based on a similar principle and can be cooled using dye molecules. These molecules act like small refrigerators and swallow the hot light particles before spitting them out again at the right temperature.
In our experiments we filled a tiny container with a dye solution, explains Dr. Julian Schmitt from the Institute of Applied Physics at the University of Bonn. The walls of the container were highly reflective. The researchers then excited the dye molecules with a laser. This produced photons that bounced back and forth between the reflective surfaces. As the particles of light repeatedly collided with dye molecules, they cooled down and finally condensed into a quantum gas.
This process still continues afterward, however, and the particles of the super photon repeatedly collide with the dye molecules, being swallowed up before being spat out again. Therefore, the quantum gas sometimes contains more and sometimes less photons, making it flicker like a candle. We used this flickering to investigate whether an important theorem of physics is valid in a quantum gas system, says Schmitt.
This so-called regression theorem can be illustrated by a simple analogy: Let us assume that the super photon is a campfire that sometimes randomly flares up very strongly. After the fire blazes particularly brightly, the flames slowly die down and the fire returns to its original state. Interestingly, one can also cause the fire to flare up intentionally by blowing air into the embers. In simple terms, the regression theorem predicts that the fire will then continue to burn down in the same way as if the flare up had occurred at random. This means that it responds to the perturbation in exactly the same way as it fluctuates on its own without any perturbation.
Blowing Air Into a Photon Fire
We wanted to find out whether this behavior also applies to quantum gases, explains Schmitt, who is also a member of the transdisciplinary research area (TRA) Building Blocks of Matter and the Matter and Light for Quantum Computing Cluster of Excellence at the University of Bonn. For this purpose, the researchers first measured the flickering of the super photons to quantify the statistical fluctuations. They then figuratively speaking blew air into the fire by briefly firing another laser at the super photon. This perturbation caused it to briefly flare up before it slowly returned to its initial state.
We were able to observe that the response to this gentle perturbation follows precisely the same dynamics as the random fluctuations without a perturbation, says the physicist. In this way we were able to demonstrate for the first time that this theorem also applies to exotic forms of matter as quantum gases. Interestingly, this is also the case for strong perturbations. Systems usually respond differently to stronger perturbations than they do to weaker ones an extreme example is a layer of ice that will suddenly break when the load placed on it becomes too heavy. This is called nonlinear behavior, says Schmitt. However, the theorem remains valid in these cases, as we have now been able to demonstrate together with our colleagues from the University of Antwerp.
The findings are of huge relevance for fundamental research with photonic quantum gases because one often does not know precisely how they will flicker in their brightness. It is much easier to determine how the super photon responds to a controlled perturbation. This allows us to learn about unknown properties under very controlled conditions, explains Schmitt. It will enable us, for example, to find out how novel photonic materials consisting of many super photons behave at their core.
Reference: Observation of nonlinear response and Onsager regression in a photon Bose-Einstein condensate by Alexander Sazhin, Vladimir N. Gladilin, Andris Erglis, Gran Hellmann, Frank Vewinger, Martin Weitz, Michiel Wouters and Julian Schmitt, 3 June 2024, Nature Communications. DOI: 10.1038/s41467-024-49064-9
The Institute of Applied Physics at the University of Bonn, the University of Antwerp (Belgium) and the University of Freiburg participated in the study. The project was supported by the German Research Foundation (DFG), the European Union (ERC Starting Grant), the German Aerospace Centre (DLR) and the Belgium funding agency FWO Flanders.
See the original post:
Quantum Magic: How Super Photons Are Shaping the Future of Physics - SciTechDaily
What "naked" singularities are revealing about quantum space-time – New Scientist
Adobe Stock/Erika Eros/Alamy/Collage: Ryan Wills
Deep inside a black hole, the cosmos gets twisted beyond comprehension. Here, at some infinitesimal point of infinite density, the fabric of the universe gets so ludicrously warped that Albert Einsteins general theory of relativity, which describes how mass bends space-time, ceases to make sense. At the singularity, our understanding falls apart.
As daunting as singularities are, each one is at least safely tucked away inside the event horizon of a black hole, the boundary beyond which we cant see. This not only cloaks them from view, but also stops unknown effects they herald, namely the horrors of unpredictability, from leaching out into the wider universe. But what if singularities could exist outside black holes after all?
That question, given fresh impetus in recent years by demonstrations that general relativity allows for this, has spurred theorists to probe singularities from a deeper perspective, folding in insights from the latest forays into the possible quantum foundations of gravity. Already, they are realising that this new approach flips the script on how we think about singularities, says Netta Engelhardt at the Massachusetts Institute of Technology.
Fair warning: the work takes us into some labyrinthine physics. But by grappling with singularities in this way, Engelhardt and her colleagues are deciphering the enigmatic connections between the quantum realm and classical gravity and reinforcing the revolutionary idea that
Read the rest here:
What "naked" singularities are revealing about quantum space-time - New Scientist
CERN welcomes International Year of Quantum Science and Technology – CERN
On the centenary of quantum mechanics -- the bedrock of particle physics and enabler of numerous technologies CERN is contributing to the development of a new generation of quantum technologies for fundamental research and beyond.
100 years ago, a handful of visionary physicists upturned notions about nature that had guided scientists for centuries. Particles can be point- or wave-like, depending on how you look at them. Their behaviour is probabilistic and can momentarily appear to violate cherished laws such as the conservation of energy. Particles can be entangled such that one feels the change of state of the other instantaneously no matter the distance between them, and, as befalls Schrdinger's famous cat, they can be in opposite states at the same time.
Today, thanks to pioneering theoretical and experimental efforts to understand this complex realm, physicists can confidently navigate through such apparently irrational concepts. Quantum theory has not only become foundational to physics, chemistry, engineering and biology, but underpins the transistors, lasers and LEDs that drive modern electronics and telecommunications -- not to mention solar cells, medical scanners and global positioning systems. But this is only the beginning.
On 7 June the United Nations declared 2025 the International Year of Quantum Science and Technology to celebrate the contributions of quantum science to technological progress, raise awareness of its importance to sustainable development, and ensure that all nations have access to quantum education and opportunities. As the worlds largest particle physics lab, CERN has been interrogating the quantum theories that govern the microscopic world for the past 70 years. Most recently, it has entered the rapidly growing domain of quantum technologies, which aims to harness the strangest aspects of quantum mechanics to build a new generation of quantum devices for fundamental research and beyond.
In recent years, we have learned not just to use the properties of the quantum world but, also, to control them, explains Sofia Vallecorsa, coordinator of the CERN Quantum Technology Initiative (QTI). Today, the revolution is all about controlling individual quantum systems, such as single atoms or ions, enabling even more powerful applications.
At CERN, quantum technologies are studied and developed through two initiatives: the QTI, whose aim is to enable technologies such as quantum computing, quantum state sensors, time synchronisation protocols, and many more for high-energy physics activities; and the recently established Open Quantum Institute (OQI), whose aim is to identify, support and accelerate the development of future societal applications benefiting from quantum computing algorithms.
One of the most promising fields is quantum computing. Unlike conventional computers that use bits that can be in one of just two states, quantum computers using qubits which can exist in superpositions of states. This enables a vast number of computations to be processed simultaneously, offering important applications in fields such as cryptography, logistics and process optimisation, and drug discovery. Quantum communication, which exploits the principles of quantum mechanics to make it impossible to intercept information without detection, is another significant area of development. A third pillar of CERNs quantum-technologies programme is sensing to allow ultra-precise measurements of physical quantities, with potential applications in fields including medicine, navigation and climate science.
What started 100 years ago as a purely theoretical physics investigation is now beginning to unleash its full potential, says OQI coordinator Tim Smith of CERN. The International Year of Quantum Science and Technology will be a wonderful opportunity to celebrate the past, the present and the future of our understanding of the quantum world.
Continued here:
CERN welcomes International Year of Quantum Science and Technology - CERN
New Method Enhances the Accuracy of Quantum Calculations – AZoQuantum
In an article recently published in the journal Communications Physics, researchers investigated the feasibility of calculating high-accuracy, finite-size effect-free hyperfine tensors using an improved integration method for the case of the nitrogen-vacancy (NV) center in diamond.
Point defects are widely utilized to manipulate the electronic and optical characteristics of semiconductors. Recently, the introduction of paramagnetic defects has begun to alter the magnetic properties of these materials, revealing a range of mesoscopic and microscopic magnetic phenomena.
By reducing the concentration of defects, controllable few-spin systems can be established, facilitating the creation of quantum nodes and qubits based on point defects. In wide-bandgap semiconductors, these point defect qubits exhibit robustness and high coherence, even at elevated temperatures.
The optically addressable spin qubits, exemplified by the silicon vacancy in silicon carbide and the NV center in diamond, maintain prolonged coherence times at room temperature. Consequently, point defect quantum devices are increasingly prominent in various quantum technology applications, including quantum internet and quantum sensin.
In light element semiconductors, the coherence of spin qubits is compromised by interactions with nuclear spins and paramagnetic defects. In high-purity samples, the magnetic environment of a spin qubit is predominantly influenced by the surrounding nuclear spin bath.
The interaction between point defect spins and nuclear spins is mediated through hyperfine coupling, which is determined by the positions of the nuclear spins and the spatial distribution of the defect's spin density. The hyperfine tensor, which parameterizes the hyperfine term in the spin Hamiltonian, is crucial in this interaction. The elements of the hyperfine tensor can be both calculated using first-principles electronic structure methods and measured via various magnetic resonance techniques.
While the accuracy of the calculated hyperfine tensors or parameters is impressive for nuclear spins close to the defectwithin 1-5 the precision diminishes significantly for nuclear spins positioned at greater distances. This decrease in accuracy is largely due to periodic boundary conditions and the limitations of finite-size effects.
In this study, researchers employed a first-principles code, widely recognized in the industry, to demonstrate that the computed hyperfine parameters' absolute relative error can surpass 100% for the NV center in diamond. They initially showcased the numerical inaccuracies in the hyperfine parameters using the industry-standard VASP code.
To address the methodological shortcomings, the team introduced a real-space integration method and employed a substantially large support lattice that accounted for nuclear spins beyond the supercell boundaries. They conducted extensive calculations for the NV center in diamond using different exchange-correlation functionals and benchmarked their results against existing experimental hyperfine datasets.
For these calculations, diamond supercells containing 1728 and 512 atoms with a central NV center were used. The researchers utilized the Heyd-Scuseria-Ernzerhof (HSE06) and Perdew-Burke-Ernzerhof (PBE) exchange-correlation functionals, applied stringent convergence criteria, and performed -point sampling of the Brillouin zone with a 500 eV cutoff energy for the plane-wave basis set.
The energy threshold for the self-consistent field calculations was set at 10-6 eV for the self-consistent field calculations, and the defect structure was optimized until the most significant force fell below 10-3 eV/. For the hyperfine tensor calculations in real space, the convergent spin density from the 1728-atom supercell model was utilized. This model was defined on a finely spaced real-space grid of 0.036 , processed through VASP.
By implementing the proposed method, researchers achieved a significant enhancement in hyperfine values, achieving a nearly 100-fold reduction in the mean absolute relative error (MARE) compared to the industry-standard VASP code. This substantial improvement was characterized by markedly lower relative mean errors across all measured distances.
In particular, the application of the Heyd-Scuseria-Ernzerhof (HSE06) functional with a 0.2 mixing parameter demonstrated optimal performance for the NV center in diamond, yielding a mean absolute percentage error of just 1.7 % for nuclear spins located 6-30 from the NV center. This performance markedly surpassed previous theoretical predictions using VASP, indicating a significant advancement in the accuracy of hyperfine calculations.
The study further highlighted that the remaining discrepancies in the results could likely be attributed to inaccuracies in calculating the Fermi contact term. Moreover, researchers provided highly accurate hyperfine tensors for 104 lattice sites and volumetric hyperfine data with a spatial resolution finer than 0.1 . This level of precision is critical for the high-accuracy simulation of NV center quantum nodes, which are pivotal in quantum information processing and for accurately positioning nuclear spins through the comparison of experimental and theoretical hyperfine data.
In summary, this study confirmed that high-accuracy, finite-size effect-free hyperfine tensors can be computed effectively using the proposed integration method. These findings suggest that even more precise theoretical hyperfine data could be obtained by further enhancing numerical accuracy in larger supercells and incorporating more precise experimental data.
Takcs, I., Ivdy, V. (2024). Accurate hyperfine tensors for solid state quantum applications: Case of the NV center in diamond. Communications Physics, 7(1), 1-6. https://doi.org/10.1038/s42005-024-01668-9, https://www.nature.com/articles/s42005-024-01668-9
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.
See the article here:
New Method Enhances the Accuracy of Quantum Calculations - AZoQuantum
Clash Between General Relativity and Quantum Mechanics Could Be Resolved by New Mathematical Framework – The Debrief
One of the greatest challenges in modern physics involves reconciling apparent conflicts between general relativity and quantum mechanics, which are largely viewed as incompatible due to their differing concepts of space and time.
However, innovative new research is finally suggesting that a resolution to these longstanding differences could be on the horizon, with the introduction of a more advanced mathematical framework that may finally help unite these two fundamental theories.
In general relativity, Einstein envisioned a gently curved spacetime, where time is relative to the perspective of an observer in relation to time and space. By comparison, the realm of quantum mechanics presents a chaotic view of the universe on the microscopic scale, where time is essentially absolute and universal.
Because of these issues, Einstein had a somewhat turbulent relationship with the theory of quantum mechanics, which, ironically, resulted largely from work by Erwin Schrdinger that drew from Einsteins later studies of atoms, molecules, and light. The apparent random chaos inherent in quantum mechanics prompted one of Einsteins most famous axioms, where he expressed that God does not play dice with the universe, also insisting that perfect laws in the world of things existing as real objects seemingly in contrast to the chaotic and unpredictable nature of quantum physics.
However, new research is offering fresh insights into the long-held divide between these differing perspectives of our universe.
According to Einsteins theory, gravity is not a force but emerges due to the geometry of the four-dimensionalspacetime continuum, or spacetime for short, says researcher Sjors Heefer, whose recent Ph.D. research involved studies of gravity that have not only led to new possibilities in gravity wave research but also to a potential reconciliation between the quantum and relativistic worlds.
At the heart of Heefers research, which explores the role of gravity on a universal scale, is the relationship between matter and spacetime. An often relied-on summary of Einsteins general theory of relativity dictates that matter tells spacetime how to curve, and curved spacetime tells matter how to move. However, this well-defined way of explaining gravity in general relativity falls short when it comes to quantum mechanics.
Heefers focus on gravitational waves examines their implications in relativistic terms and quantum mechanics. Gravitational waves arise from the curvature in spacetime that Einstein envisioned and are essentially the ripples caused by massive objects or events like stellar collisions and black holes.
In quantum mechanics, particles differ significantly from the relativistic view in that they can exist simultaneously in multiple states until they collapse at random into a single state when under observation. This mysterious probabilistic nature is observed in all matter and forces in the universe, except for gravity, a fact that presents one of the most significant challenges for modern physicists.
One potential way of resolving the issue would involve an expansion of the current mathematical framework used to describe general relativity. Although traditionally physicists have relied on what is known as pseudo-Riemannian geometry for describing relativistic phenomena, recent research has increasingly pointed to a more advanced mathematical language known as Finsler geometry as being better equipped at expressing the profound oddity of our universe.
In physics, fields describe values at each point in space and time, whereas gravitational fields represent the curvature of spacetime. In his Ph.D. research, Heefer delved into the challenging work of attempting to solve field equations in Finsler gravity, specifically looking at the vacuum field equation of Christian Pfeifer and Mattias N. R. Wohlfarth, an equation that relates to governing the gravitational field in empty space. Specifically, the equation describes the potential shapes spacetime geometry may take when no matter is present.
To good approximation, this includes all interstellar space between stars and galaxies, as well as the empty space surrounding objects such as the sun and the Earth, Heefer said in a recent statement. By carefully analyzing the field equation, several new types of spacetime geometries have been identified.
According to Heefers research, observations of gravitational waves in recent years do appear to complement the hypothesis that spacetime works in accordance with Finsler gravity, presenting an expanded mathematical framework that could potentially also help to reconcile the seemingly disparate worlds of general relativity and quantum mechanics.
While Heefers findings are promising, they represent only the beginning of exploring Finsler gravitys implications, as well as efforts to resolve the relativistic and quantum worlds.
However, Heefer says he is optimistic that our results will prove instrumental in deepening our understanding of gravity, adding that he hopes that with time, they may even shine light on the reconciliation of gravity with quantum mechanics.
Heefers research is outlined in Finsler Geometry, Spacetime & Gravity, recently published by the Eindhoven University of Technology in the Netherlands.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email atmicah@thedebrief.org. Follow his work atmicahhanks.comand on X:@MicahHanks.
Go here to read the rest:
Quantum computer photons create a vortex when they collide – Earth.com
Scientists have stumbled upon a remarkable discovery that challenges our understanding of the quantum world. New research revealed the existence of a previously unknown type of vortex that emerges when photons, the elusive particles of light, engage in a mesmerizing dance of interaction.
The implications of this finding extend far beyond the realm of pure science, holding the potential to revolutionize the field of quantum computing.
The research team, led by a brilliant quartet of scientists Dr. Lee Drori, Dr. Bankim Chandra Das, Tomer Danino Zohar, and Dr. Gal Winer embarked on this journey of discovery in the hallowed halls of Prof. Ofer Firstenbergs laboratory at the Weizmann Institute of Sciences Physics of Complex Systems Department.
Their initial goal was to explore efficient ways of harnessing the power of photons for data processing in quantum computers.
Little did they know that their quest would lead them down an unexpected path, into a world where the rules of classical physics are bent and the secrets of the quantum realm are laid bare.
Photons, the fundamental particles of light, are known for their wave-like behavior. However, getting them to interact with each other is no easy feat. It requires the presence of matter that acts as an intermediary.
To create the perfect environment for photon interactions, the researchers designed a unique setup: a 10-centimeter glass cell containing a dense cloud of rubidium atoms, tightly packed in the center.
As photons passed through this cloud, the researchers closely examined their state to see if they had influenced one another.
When the photons pass through the dense gas cloud, they send a number of atoms into electronically excited states known as Rydberg states, Prof. Firstenberg explains.
He goes on to describe how, in these Rydberg states, a single electron within the atom begins to orbit at an astonishing distance, up to 1,000 times the diameter of an unexcited atom.
This electron, with its vastly expanded orbit, generates an electric field so powerful that it envelops and influences countless neighboring atoms, effectively transforming them into what Prof. Firstenberg poetically refers to as an imaginary glass ball.'
As the researchers delved deeper into the interactions between photons, they stumbled upon something extraordinary.
When two photons passed relatively close to each other, they moved at a different speed than they would have if each had been traveling alone. This change in speed altered the positions of the peaks and valleys of the waves they carried.
In the ideal scenario for quantum computing applications, the positions of the peaks and valleys would become completely inverted relative to one another, a phenomenon known as a 180-degree phase shift. However, what the researchers observed was even more fascinating.
When the gas cloud was at its densest and the photons were in close proximity, they exerted the highest level of mutual influence.
But as the photons moved away from each other or the atomic density around them decreased, the phase shift weakened and disappeared.
Instead of a gradual process, the researchers were surprised to find that a pair of vortices developed when two photons were a certain distance apart.
To visualize photon vortices, imagine dragging a vertically held plate through water. The rapid movement of the water pushed by the plate meets the slower movement around it, creating two vortices that appear to be moving together along the waters surface.
In reality, these vortices are part of a three-dimensional configuration called a vortex ring.
The researchers discovered that the two vortices observed when measuring two photons are part of a three-dimensional vortex ring generated by the mutual influence of three photons.
These findings showcase the striking similarities between the newly discovered vortices and those found in other environments, such as smoke rings.
While the discovery of photon vortices has taken center stage, the researchers remain dedicated to their original goal of advancing quantum data processing.
The next phase of their study will involve firing photons into each other and measuring the phase shift of each photon separately.
The strength of these phase shifts could determine the potential for photons to be used as qubits, the basic units of information in quantum computing.
Unlike regular computer memory units, which can only be 0 or 1, quantum bits have the ability to represent a range of values between 0 and 1 simultaneously.
The prevalent assumption was that this weakening would be a gradual process, but researchers were in for a surprise, Dr. Eilon Poem and Dr. Alexander Poddubny, key contributors to the study, reveal.
They go on to describe the astonishing discovery that when two photons reached a specific distance from each other, a pair of vortices spontaneously emerged.
These vortices, characterized by a complete 360-degree phase shift of the photons, featured a peculiar void at their center, eerily reminiscent of the dark, calm eye found at the heart of other well-known vortices in nature.
The journey that led to this discovery spanned eight years and saw two generations of doctoral students pass through Prof. Firstenbergs laboratory.
Over time, the Weizmann scientists successfully created a dense, ultracold gas cloud packed with atoms, enabling them to achieve the unprecedented: photons that underwent a phase shift of 180 degrees or more.
As the research team continues to unravel the mysteries of photon interactions and their potential applications in quantum computing, one thing is certain: their findings have opened up a new realm of possibilities in the world of physics and beyond.
The full study was published in the journal Science.
Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
Visit link:
Quantum computer photons create a vortex when they collide - Earth.com
New technique could help build quantum computers of the future – EurekAlert
image:
Kaushalya Jhuria in the lab testing the electronics from the experimental setup used to make qubits in silicon.
Credit: Thor Swift/Berkeley Lab
Quantum computers have the potential to solve complex problems in human health, drug discovery, and artificial intelligence millions of times faster than some of the worlds fastest supercomputers. A network of quantum computers could advance these discoveries even faster. But before that can happen, the computer industry will need a reliable way to string together billions of qubits or quantum bits with atomic precision.
Connecting qubits, however, has been challenging for the research community. Some methods form qubits by placing an entire silicon wafer in a rapid annealing oven at very high temperatures. With these methods, qubits randomly form from defects (also known as color centers or quantum emitters) in silicons crystal lattice. And without knowing exactly where qubits are located in a material, a quantum computer of connected qubits will be difficult to realize.
But now, getting qubits to connect may soon be possible. A research team led by Lawrence Berkeley National Laboratory (Berkeley Lab) says that they are the first to use a femtosecond laser to create and annihilate qubits on demand, and with precision, by doping silicon with hydrogen.
The advance could enable quantum computers that use programmable optical qubits or spin-photon qubits to connect quantum nodes across a remote network. It could also advance a quantum internet that is not only more secure but could also transmit more data than current optical-fiber information technologies.
To make a scalable quantum architecture or network, we need qubits that can reliably form on-demand, at desired locations, so that we know where the qubit is located in a material. And that's why our approach is critical, said Kaushalya Jhuria, a postdoctoral scholar in Berkeley Labs Accelerator Technology & Applied Physics (ATAP) Division. She is the first author on a new study that describes the technique in the journal Nature Communications. Because once we know where a specific qubit is sitting, we can determine how to connect this qubit with other components in the system and make a quantum network.
This could carve out a potential new pathway for industry to overcome challenges in qubit fabrication and quality control, said principal investigator Thomas Schenkel, head of the Fusion Science & Ion Beam Technology Program in Berkeley Labs ATAP Division. His group will host the first cohort of students from the University of Hawaii in June as part of a DOE Fusion Energy Sciences-funded RENEW project on workforce development where students will be immersed in color center/qubit science and technology.
Forming qubits in silicon with programmable control
The new method uses a gas environment to form programmable defects called color centers in silicon. These color centers are candidates for special telecommunications qubits or spin photon qubits. The method also uses an ultrafast femtosecond laser to anneal silicon with pinpoint precision where those qubits should precisely form. A femtosecond laser delivers very short pulses of energy within a quadrillionth of a second to a focused target the size of a speck of dust.
Spin photon qubits emit photons that can carry information encoded in electron spin across long distances ideal properties to support a secure quantum network. Qubits are the smallest components of a quantum information system that encodes data in three different states: 1, 0, or a superposition that is everything between 1 and 0.
With help from Boubacar Kant, a faculty scientist in Berkeley Labs Materials Sciences Division and professor of electrical engineering and computer sciences (EECS) at UC Berkeley, the team used a near-infrared detector to characterize the resulting color centers by probing their optical (photoluminescence) signals.
What they uncovered surprised them: a quantum emitter called the Ci center. Owing to its simple structure, stability at room temperature, and promising spin properties, the Ci center is an interesting spin photon qubit candidate that emits photons in the telecom band. We knew from the literature that Ci can be formed in silicon, but we didnt expect to actually make this new spin photon qubit candidate with our approach, Jhuria said.
The researchers learned that processing silicon with a low femtosecond laser intensity in the presence of hydrogen helped to create the Ci color centers. Further experiments showed that increasing the laser intensity can increase the mobility of hydrogen, which passivates undesirable color centers without damaging the silicon lattice, Schenkel explained.
A theoretical analysis performed by Liang Tan, staff scientist in Berkeley Labs Molecular Foundry, shows that the brightness of the Ci color center is boosted by several orders of magnitude in the presence of hydrogen, confirming their observations from laboratory experiments.
The femtosecond laser pulses can kick out hydrogen atoms or bring them back, allowing the programmable formation of desired optical qubits in precise locations, Jhuria said.
The team plans to use the technique to integrate optical qubits in quantum devices such as reflective cavities and waveguides, and to discover new spin photon qubit candidates with properties optimized for selected applications.
Now that we can reliably make color centers, we want to get different qubits to talk to each other which is an embodiment of quantum entanglement and see which ones perform the best. This is just the beginning, said Jhuria.
The ability to form qubits at programmable locations in a material like silicon that is available at scale is an exciting step towards practical quantum networking and computing, said Cameron Geddes, Director of the ATAP Division.
Theoretical analysis for the study was performed at the Department of EnergysNational Energy Research Scientific Computing Center (NERSC) at Berkeley Lab with support from the NERSC QIS@Perlmutterprogram.
The Molecular Foundry and NERSC are DOE Office of Science user facilities at Berkeley Lab.
This work was supported by the DOE Office of Fusion Energy Sciences.
###
Lawrence Berkeley National Laboratory (Berkeley Lab) is committed to delivering solutions for humankind through research in clean energy, a healthy planet, and discovery science. Founded in 1931 on the belief that the biggest problems are best addressed by teams, Berkeley Lab and its scientists have been recognized with 16 Nobel Prizes. Researchers from around the world rely on the Labs world-class scientific facilities for their own pioneering research. Berkeley Lab is a multiprogram national laboratory managed by the University of California for the U.S. Department of Energys Office of Science.
DOEs Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visitenergy.gov/science.
Nature Communications
Experimental study
Not applicable
Programmable quantum emitter formation in silicon
27-May-2024
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.
Follow this link:
New technique could help build quantum computers of the future - EurekAlert