Some of the most exciting topics in modern physics, such as some proposals of high temperature superconductors and quantum computers, are attributed to the strange things that occur when these systems hover between the two quantum states.
Unfortunately, it turns out that what happened at these points (called quantum critical point) is challenging. Mathematics is often too difficult to solve. Today’s computers do not always simulate what happened, especially in a system involving any considerable quantity atoms.
Now, researchers and colleagues of the SLAC National Accelerator Laboratory of Stanford University and Energy Department have taken one step towards the establishment of an alternative method called a quantum simulator. Although the new equipment can only simulate the interaction between two quantum objects, the researchers pointed out in a paper in the magazine of Nature Physics on January 30 that it can be relatively easy to easily easily easily Apricate by proportion. If so, researchers can use it to simulate a more complex system and start answering some of the most attractive questions in physics.
“We have been making mathematical models. We hope that these models can capture the essence of the phenomenon we are interested in, but even if we believe that they are correct, they usually cannot solve David Goldhaber-Gordon, a professor at a professor of physics and the Institute of Stanford Materials and Energy Sciences (SIMES), said. He said that with the path to the quantum simulator, “we have these knobs that have never been before.”
Island in the Electronic Sea
Goldhaber-Gordon said that the basic concept of quantum simulator is similar to the mechanical model of the solar system. Some people rotate the crank and lock the gear rotation to represent the movement of the moon and the planet. The “solar instrument” found in the wreckage of the shipwreck more than 2000 years ago was considered to have a quantitative prediction of day eclipse time and planet’s location in the sky, and similar machines were used in mathematics calculations in the late 20th century. This is too much. This was difficult for the most advanced digital computer at the time.
Just like the designer of the solar mechanical model, researchers who build a quantum simulator need to ensure that their simulator is reasonably aligned with the mathematical model they want to simulate.
For Goldhaber-Gordon and his colleagues, many systems they are interested in — systems with quantum critical points, such as some superconductors-can be imagined as an atom of an element, they are arranged in the mobile electronics library embedded in the mobile electronic library In cyclical lattice. The lattice atoms in this material are the same, they interact with each other and interact with the surrounding electronic sea.
To use the quantum simulator to model such materials, the simulator needs to have alternatives with almost the same lattice atoms with each other, and a strong interaction between these atoms and the surrounding electronic library needs to occur. The system also needs to be adjusted in some way so that the experiments can change the different parameters of the experiment to understand the simulation in depth.
Winston Pouse, a graduate student at Goldhaber-Gordon laboratory and the first author of the thesis of Natural Physics, said that most of the quantum simulation proposals cannot meet all these requirements at the same time. “At high levels, there are ultra -cold atoms. The atoms are exactly the same, but it is difficult to achieve strong coupling with the reservoir. Then there is a quantum -based simulator. We can achieve strong coupling in them, but the site is not complete Same, “said.
Goldhaber-Gordon said that French physicist Frédéric Pierre’s work proposed a possible solution. He is studying nano-level devices. Among these devices, metal island is located specially designed electronics. Between the pools, it is called a two -dimensional electronic gas. Electronic flow between the voltage control door adjustment pool and metal island.
When studying Pierre and his laboratory work, Pouse, Goldhaber-Gordon, and their colleagues realized that these devices could meet their standards. These islands -alternatives of latheomic atoms -have a strong interaction with the electronics around them. If Pierre’s single island is expanded to two or more islands clusters, they will also occur between them. Strong interaction. Compared with other materials, metal islands also have a large number of electronics, which has any significant differences between the two different invisible tiny blocks of the same metal -make them the same. Finally, the system can be tuned by controlling the wire of the voltage.
A simple simulator
The team also realized that by pairing Pierre’s metal island, they can create a simple system that should show the critical quantum critical phenomenon they are interested in.
It turns out that one of the difficult parts is actually manufacturing equipment. First of all, the basic contour of the circuit must be carved into semiconductors with nano -level. Then someone must deposit a small metal and melt the bottom layer structure to create each metal island.
“It is difficult for them to make,” Pouse said when talking about these devices. “This is not a super cleaning process. It is important to establish a good contact between metal and semiconductor below.”
Despite these difficulties, the team’s job is part of Stanford University and SLAC’s wider range of quantum science work. They can build a device with two metal islands and study how electronics can pass it under various conditions. Their results are consistent with the calculation of a few weeks of spending on supercomputes -suggesting that they may have found a way to study quantum critical phenomena more effectively than before.
The theoretical physicist Andrew Mitchell, a theoretical physicist at the University of Dublin University of Dublin (C), said: “Although we have not built a general programming that can solve the problem Quantum computer. -Quest) and the author of the paper, “We can now build a customized simulation equipment with quantum components to solve specific quantum physical problems. ”
In the end, Goldhaber-Gordon said that the team hopes to build more and more islands devices so that they can simulate the basic behavior of increasingly and larger atoms and capture real materials.
However, first of all, they want to improve the design of their twin island devices. One goal is to reduce the size of the metal island, which can better run them at the temperature that can be achieved: the cut -end ultra -low -temperature “refrigerator” can reduce the temperature to one in the absolute zero, but this is almost almost almost Not enough cold experiments that researchers have just completed. Another method is to develop a more reliable process than dripping the melted metal to the semiconductor to create the island.
However, researchers believe that once these problems are solved, their work can lay the foundation for physicists’ understanding of certain types of superconductors, and may even lay the foundation for more strange physics, such as simulating particles that simulate particles Assuming that there is only a small part of a small part of the charge of the quantum state.
Pouse said: “One of the things I shared with me is to express appreciation for such experiments and even possible facts,” “I am very excited about the future.”