Some of the most exciting topics in modern physics, such as high-temperature superconductors and some proposals for quantum computers, come down to the exotic things that happen when these systems hover between two quantum states.
Unfortunately, understanding what's happening at those points, known as quantum critical points, has proved challenging. The math is frequently too hard to solve, and today's computers are not always up to the task of simulating what happens, especially in systems with any appreciable number of atoms involved.
Now, researchers at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory and their colleagues have taken a step toward building an alternative approach, known as a quantum simulator. Although the new device, for now, only simulates the interactions between two quantum objects, the researchers argue in a paper published January 30 in Nature Physics that it could be scaled up relatively easily. If so, researchers could use it to simulate more complicated systems and begin answering some of the most tantalizing questions in physics.
"We're always making mathematical models that we hope will capture the essence of phenomena we're interested in, but even if we believe they're correct, they're often not solvable in a reasonable amount of time" with current methods, said David Goldhaber-Gordon, a professor of physics at Stanford and a researcher with the Stanford Institute for Materials and Energy Sciences (SIMES). With a path toward a quantum simulator, he said, "we have these knobs to turn that no one's ever had before."
Islands in a sea of electrons
The essential idea of a quantum simulator, Goldhaber-Gordon said, is sort of similar to a mechanical model of the solar system, where someone turns a crank, and interlocking gears rotate to represent the motion of the moon and planets. Such an "orrery" discovered in a shipwreck dating back more than 2000 years is thought to have produced quantitative predictions of eclipse timings and planetary locations in the sky, and analogous machines were used even into the late 20th century for mathematical calculations that were too hard for the most advanced digital computers at the time.
Like the designers of a mechanical model of a solar system, researchers building quantum simulators need to make sure that their simulators line up reasonably well with the mathematical models they're meant to simulate.
For Goldhaber-Gordon and his colleagues, many of the systems they are interested in—systems with quantum critical points such as certain superconductors—can be imagined as atoms of one element arranged in a periodic lattice embedded within a reservoir of mobile electrons. The lattice atoms in such a material are all identical, and they all interact with each other and with the sea of electrons surrounding them.
To model materials like that with a quantum simulator, the simulator needs to have stand-ins for the lattice atoms that are nearly identical to each other, and these need to interact strongly with each other and with a surrounding reservoir of electrons. The system also needs to be tunable in some way, so that experimenters can vary different parameters of the experiment to gain insight into the simulation.
Most quantum simulation proposals don't meet all of those requirements at once, said Winston Pouse, a graduate student in Goldhaber-Gordon's lab and first author of the Nature Physics paper. "At a high level, there are ultracold atoms, where the atoms are exactly identical, but implementing a strong coupling to a reservoir is difficult. Then there are quantum dot-based simulators, where we can achieve a strong coupling, but the sites are not identical," Pouse said.
Goldhaber-Gordon said a possible solution arose in the work of French physicist Frédéric Pierre, who was studying nanoscale devices in which an island of metal was situated between specially designed pools of electrons known as two-dimensional electron gases. Voltage-controlled gates regulated the flow of electrons between the pools and the metal island.
In studying Pierre and his lab's work, Pouse, Goldhaber-Gordon and their colleagues realized these devices could meet their criteria. The islands—stand-ins for the lattice atoms—interacted strongly with the electron gases around them, and if Pierre's single island were expanded to a cluster of two or more islands they would interact strongly with each other as well. The metal islands also have a vastly larger number of electronic states compared with other materials, which has the effect of averaging out any significant differences between two different invisibly tiny blocks of the same metal—making them effectively identical. Finally, the system was tunable through electric leads that controlled voltages.
A simple simulator
The team also realized that by pairing up Pierre's metal islands, they could create a simple system that ought to display something like the quantum critical phenomenon they were interested in.
One of the hard parts, it turned out, was actually building the devices. First, the basic outlines of the circuit have to be nanoscopically etched into semiconductors. Then, someone has to deposit and melt a tiny blob of metal onto the underlying structure to create each metal island.
"They're very difficult to make," Pouse said of the devices. "It's not a super clean process, and it's important to make a good contact" between the metal and the underlying semiconductor.
Despite those difficulties, the team, whose work is part of broader quantum science efforts at Stanford and SLAC, was able to build a device with two metal islands and examine how electrons moved through it under a variety of conditions. Their results matched up with calculations which took weeks on a supercomputer—hinting that they may have found a way to investigate quantum critical phenomena much more efficiently than before.
"While we have not yet built an all-purpose programmable quantum computer with sufficient power to solve all of the open problems in physics," said Andrew Mitchell, a theoretical physicist at University College Dublin's Centre for Quantum Engineering, Science, and Technology (C-QuEST) and a co-author on the paper, "we can now build bespoke analogue devices with quantum components that can solve specific quantum physics problems."
Eventually, Goldhaber-Gordon said, the team hopes to build devices with more and more islands, so that they can simulate larger and larger lattices of atoms, capturing essential behaviors of real materials.
First, however, they are hoping to improve the design of their two-island device. One aim is to decrease the size of the metal islands, which could make them operate better at accessible temperatures: cutting-edge ultralow temperature "refrigerators" can reach temperatures down to a fiftieth of a degree above absolute zero, but that was barely cold enough for the experiment the researchers just finished. Another is to develop a more reliable process for creating the islands than essentially dripping molten bits of metal onto a semiconductor.
But once kinks like those are worked out, the researchers believe, their work could lay the foundation for significant advances in physicists' understanding of certain kinds of superconductors and perhaps even more exotic physics, such as hypothetical quantum states that mimic particles with only a fraction of the charge of an electron.
"One thing David and I share is an appreciation for the fact that performing such an experiment was even possible," Pouse said, and for the future, "I am certainly excited."
More information:Winston Pouse et al, Quantum simulation of an exotic quantum critical point in a two-site charge Kondo circuit, Nature Physics (2023). DOI: 10.1038/s41567-022-01905-4
Citation: Researchers take a step toward novel quantum simulators (2023, February 1) retrieved 3 February 2023 from https://techxplore.com/news/2023-02-quantum-simulators.html
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FAQs
Why do we need quantum simulators? ›
Superconducting materials
Superconductors can carry electrical currents with no loss. The superconductors we have today only work at temperatures below -100C. Quantum simulations will be crucial for developing high-temperature superconductors, which could transmit power from electrical power plants with no loss.
Quantum simulators are devices that actively use quantum effects to answer questions about model systems and, through them, real systems.
Can you simulate quantum physics? ›Quantum simulators permit the study of a quantum system in a programmable fashion. In this instance, simulators are special purpose devices designed to provide insight about specific physics problems.
What is quantum computing simulation? ›Quantum simulators are software programs that run on classical computers and act as the target machine for a Q# program, making it possible to run and test quantum programs in an environment that predicts how qubits will react to different operations.
What are the benefits of simulators? ›- Simulation allows you to explore 'what if' questions and scenarios without having to experiment on the system itself.
- It helps you to identify bottlenecks in material, information and product flows.
- It helps you to gain insight into which variables are most important to system performance.
As quantum computing can process large quantities of data, it can aid in making better decisions and predictions, such as in applications such as facial recognition, object recognition, and fraud detection.
Which is the first quantum simulator? ›QSim is the first-of-its-kind toolkit, indigenously developed in India. It meant to be a vital tool of learning and understanding the practical aspects of programming with the help of Quantum Computers. It will thus bring about a new era of Quantum Computing research in India.
Why can't quantum computers be simulated? ›Simulating a quantum computer on a classical one does indeed require a phenomenal amount of resources when no approximations are made and noise is not considered. Exact algorithms for simulating quantum computers require time or memory that grows exponentially with the number of qubits or other physical resources.
What is the difference between quantum computer and simulator? ›But how does a quantum simulator differ from a quantum computer? A quantum simulator, while unlike a gate-based or annealing-based quantum computer, consists of software programs that are used to model a larger quantum mechanical system by applying the same quantum rules on classical computers.
What is the biggest problem in quantum physics? ›The biggest challenge with quantum gravity, from a scientific point of view, is that we cannot do the experiments required. For example, a particle accelerator based on present technology would have to be larger than our whole galaxy in order to directly test the effects.
Can a quantum computer simulate a human brain? ›
A quantum computer built using giant atoms controlled by laser light may be enough to imitate some functions of the brain, such as memory and decision-making.
Can you simulate an entire universe? ›Even if we have all the information that exists, we can only calculate what a quantum object is most likely to do. Such is the nature of the quantum world. And since the entire universe is simply a collection of quantum objects, the universe itself cannot be exactly simulated.
Can quantum computers simulate life? ›Artificial intelligence applications are often inspired by our own brains; this is a form of biomimicry. This can and has been implemented to a certain extent on classical computers (using neural networks), but quantum computers offer many advantages in the simulation of artificial life.
What is quantum computing Short answer? ›What Is Quantum Computing? Quantum computing is an area of computer science that uses the principles of quantum theory. Quantum theory explains the behavior of energy and material on the atomic and subatomic levels. Quantum computing uses subatomic particles, such as electrons or photons.
What are the pros and cons of simulation? ›A model or simulation is only as good as the rules used to create it. It is very difficult to create an entirely realistic model or simulation because the rules are based on research and past events. The main disadvantage of simulations is that they aren't the real thing.
How does simulation improve learning? ›Simulations promote the use of critical and evaluative thinking. Because they are ambiguous or open-ended, they encourage students to contemplate the implications of a scenario. The situation feels real, and thus leads students to engage with the activity more enthusiastically and interactively.
How will quantum technology change the world? ›A quantum computer could open new frontiers in mathematics, revolutionizing our idea of what it means to “compute.” Its processing power could spur the development of new industrial chemicals, addressing the problems of climate change and food scarcity.
What is the main idea of quantum? ›Quantum theory states that there are only certain allowed energy states for an electron and that these are quantized. Further, it tells us that no two electrons, in the same system, can occupy the same energy state, and that all the energy states are filled from the lowest levels to the highest levels.
What are the benefits of quantum technology? ›The main advantages and strengths of quantum computers
Used correctly, quantum computers are incredibly fast and effective. They can perform calculations in a few seconds for which today's supercomputers would need decades or even millennia. This fact is also referred to by experts as quantum superiority .
The first simulation game may have been created as early as 1947 by Thomas T. Goldsmith Jr. and Estle Ray Mann. This was a straightforward game that simulated a missile being fired at a target.
What is the most powerful quantum computer in the world? ›
IBM just unveiled its most powerful quantum computer yet — a 433-qubit machine. IBM Osprey has the largest qubit count of any IBM quantum processor, more than tripling the 127 qubits on the IBM Eagle processor unveiled in 2021. IBM intends to scale up its quantum computer to over 4,000 qubits by 2025 and beyond.
Who is the father of quantum computing *? ›Deutsch, 69, became known as the “father of quantum computing” after proposing an exotic – and so far unbuildable – machine to test the existence of parallel universes. His paper in 1985 paved the way for the rudimentary quantum computers scientists are working on today.
Why did Einstein not accept quantum theory? ›Einstein saw Quantum Theory as a means to describe Nature on an atomic level, but he doubted that it upheld "a useful basis for the whole of physics." He thought that describing reality required firm predictions followed by direct observations.
What problems can quantum computers not solve? ›Not having any ability for I/O of any sort, a quantum computer has no capability for controlling real-time devices, such as process control for an industrial plant. Any real-time control would have to be made by a classical computer.
Can quantum computers become self aware? ›Quantum computers are not a magical technology that makes a machine self-aware simply because it was applied. Regardless of the computing properties of the machine, the software is still needed to make it work. It is the software that provides the functionalities needed for intelligence to emerge from machines.
Are quantum computers better than the human brain? ›Even if you don't train your quantum brain to be more creative, it's comforting to know that your brain might contain 100 billion q-bits, which would make your own brain arguably more powerful than all the digital computers in the world combined.
Does the government have a quantum computer? ›The Ministry of Defence (MoD) has acquired the government's first quantum computer. Quantum computers can make very complex calculations extremely quickly and their creators say they can solve the problems regular computers cannot.
Is there anything better than a quantum computer? ›It's safe to say, though, that as of 2022 a supercomputer is far superior in computational power, at least in doing anything commercially useful.
What are the 7 biggest unanswered questions in physics? ›- Quantum Gravity. The biggest unsolved problem in fundamental physics is how gravity and the quantum will be made to coexist within the same theory. ...
- Particle Masses. ...
- The “Measurement” Problem. ...
- Turbulence. ...
- Dark Energy. ...
- Dark Matter. ...
- Complexity. ...
- The Matter-Antimatter.
Lederman, the Higgs particle has become something of a Holy Grail of physics. Certainly its discovery would represent a great leap forward in our understanding of matter, and would also provide important clues about the very early universe.
Does quantum physics violate logic? ›
Although quantum mechanics is generally considered to be fundamentally incompatible with classical logic, it is argued here that the gap is not as great as it seems. Any classical, discrete, time reversible system can be naturally described using a quantum Hubert space, operators, and a Schrödinger equation.
Is the human brain binary or quantum? ›As a result, we can deduce that those brain functions must be quantum. "Because these brain functions were also correlated to short-term memory performance and conscious awareness, it is likely that those quantum processes are an important part of our cognitive and conscious brain functions.
How much of the brain can we simulate? ›The cerebellum, which occupies only 10% of the brain mass, contains 80% (69 billion) of all neurons (Herculano-Houzel, 2009). Thus, we could say that 80% of human-scale whole brain simulation will be accomplished when a human-scale cerebellum is built and simulated on a computer.
What is the largest brain simulation? ›elegans roundworm, the Drosophila fruit fly, and the human brain models Elysia and Spaun, which is the world's largest functional brain model and is based on the NENGO software architecture.
Do I exist in a multiverse? ›We currently have no evidence that multiverses exists, and everything we can see suggests there is just one universe — our own.
Are we in an infinite universe? ›The observable universe is finite in that it hasn't existed forever. It extends 46 billion light years in every direction from us. (While our universe is 13.8 billion years old, the observable universe reaches further since the universe is expanding). The observable universe is centred on us.
Can anything in the universe be infinite? ›The curvature of the cosmos
The geometric curve on large scales of the universe tells us about its overall shape. If the universe is perfectly geometrically flat, then it can be infinite. If it's curved, like Earth's surface, then it has finite volume.
The main advantages and strengths of quantum computers
Used correctly, quantum computers are incredibly fast and effective. They can perform calculations in a few seconds for which today's supercomputers would need decades or even millennia. This fact is also referred to by experts as quantum superiority .
The development of quantum repeaters can solve the communication problems facing the world and promote the replacement of global communication methods. Quantum communication is a perfect combination of the classical communication principle and the basic principle of quantum mechanics.
What is the future of quantum technology? ›Quantum computers are expected to be available in the market by 2030. However, more time will be required for hardware and software refinements before businesses can use them for their applications.
Can quantum computers solve any problem? ›
Yet another difficult area that quantum computers cater to is that of solving difficult combinatorics problems. The algorithms within quantum computing aim at solving difficult combinatorics problems in graph theory, number theory, and statistics. Well, the list is likely to continue in the near future.