Physics

Quantum simulators could help discover materials for high-performance electronics

Generate Peierls phases using parametric coupling on a 16-qubit superconducting processor. Credit: Nature Physics (2024). DOI: 10.1038/s41567-024-02661-3

Quantum computers have the potential to emulate complex materials, allowing researchers to better understand the physical properties that result from interactions between atoms and electrons. This could one day lead to the discovery or design of better semiconductors, insulators, or superconductors that can be used to make faster, more powerful, and more energy-efficient electronics.

However, some phenomena that occur within materials can be difficult to mimic using quantum computers, and gaps remain in the questions scientists have investigated using quantum hardware. Masu.

To fill one of these gaps, researchers at MIT have developed a technique to generate synthetic electromagnetic fields on superconducting quantum processors. The research team demonstrated the technology on a processor consisting of 16 qubits.

Their research is published in the journal Nature Physics.

By dynamically controlling how the 16 qubits in the processor are coupled together, researchers are able to emulate how electrons move between atoms in the presence of electromagnetic fields. I did. Additionally, the synthetic electromagnetic field is widely tunable, allowing scientists to investigate different material properties.

Emulating electromagnetic fields is important to fully explore the properties of materials. In the future, this technology could reveal important features of electronic systems such as conductivity, polarization, and magnetization.

“Quantum computers are powerful tools for studying the physics of materials and other quantum mechanical systems. Our research allows us to simulate more of the rich physics that has fascinated materials scientists. ,” said Ilan Rosen, MIT postdoctoral fellow and lead author of the paper. in a quantum simulator.

The study’s senior author is William D. Oliver, Henry Ellis Warren Professor of Electrical Engineering, Computer Science, and Physics, director of the Center for Quantum Engineering, leader of the Engineering Quantum Systems Group, and associate director of the Electronics Laboratory. . Oliver and Rosen will be joined by other members of the electrical engineering, computer science, and physics departments, as well as MIT Lincoln Laboratory.

quantum emulator

Companies like IBM and Google are working to build large-scale digital quantum computers that promise to outperform traditional quantum computers by running certain algorithms much faster.

But that’s not all quantum computers can do. The dynamics of qubits and their bonds can also be carefully constructed to mimic the behavior of electrons moving between atoms in solids.

“This leads to obvious applications of using superconducting quantum computers as material emulators,” says Jeffrey Glover, a research scientist at MIT and co-author of the paper.

Rather than trying to build large-scale digital quantum computers to solve extremely complex problems, researchers are using the qubits in small-scale quantum computers as analog devices, working in controlled environments. Material systems can be replicated.

“General-purpose digital quantum simulators have shown great promise, but we still have a long way to go. Analog emulation is another approach that may soon yield useful results, especially in materials research. “This is a simple and powerful application of quantum hardware,” Rosen explains. “An analog quantum emulator allows us to intentionally set a starting point and watch what unfolds over time.”

Despite their similarities to materials, materials have some important components that do not easily translate to quantum computing hardware. One such factor is the magnetic field.

In matter, electrons “live” in atomic orbitals. When two atoms get close to each other, their orbits overlap and electrons can “hop” from one atom to another. In the presence of a magnetic field, the hopping behavior becomes more complex.

Superconducting quantum computers use microwave photons hopping between qubits to mimic electrons hopping between atoms. However, since photons are not charged particles like electrons, the hopping behavior of photons remains the same within a physical magnetic field.

Since you can’t just turn on a magnetic field in a simulator, the MIT team instead employed several tricks to synthesize the field’s effects.

Processor tuning

The researchers tweaked how adjacent qubits in the processor coupled together to create the same complex hopping behavior that electromagnetic fields induce in electrons.

To do this, they slightly varied the energy of each qubit by applying different microwave signals. Typically, researchers set the qubits to the same energy, allowing photons to hop from one to the other. However, this technique dynamically changes the energy of each qubit to change how they communicate with each other.

By precisely modulating these energy levels, the researchers allowed photons to jump between qubits in the same complex way that electrons jump between atoms in a magnetic field. Additionally, the microwave signal can be fine-tuned, allowing it to emulate different electromagnetic fields with different strengths and distributions.

The researchers conducted several experiments to determine what energy to set on each qubit, how strongly to modulate it, and what microwave frequency to use.

“The most difficult part was finding the modulation settings for each qubit so that all 16 qubits operated simultaneously,” Rosen says.

Once we reached the appropriate settings, we confirmed that the photon dynamics supported some of the equations that form the basis of electromagnetism. They also demonstrated the “Hall effect,” a conduction phenomenon that exists in the presence of electromagnetic fields.

These results show that the synthetic electromagnetic field behaves like the real thing.

In the future, this technology could be used to accurately study complex phenomena in condensed matter physics, such as the phase transitions that occur when a material changes from a conductor to an insulator.

“A great feature of our emulator is that it can mimic different material systems simply by changing the amplitude or frequency of the modulation. This method allows us to simulate many material properties without physically manufacturing a new device each time. and model parameters,” says Oliver.

Although this study was the first demonstration of synthetic electromagnetic fields, Rosen says it opened the door to many potential discoveries.

“The advantage of quantum computers is that we can see exactly what is happening on every qubit at every moment. So we have all this information at our disposal. We are very excited about the future. ” he added.

Further information: Ilan T. Rosen et al., Synthetic magnetic vector potential in 2D superconducting qubit arrays, Nature Physics (2024). DOI: 10.1038/s41567-024-02661-3

Provided by Massachusetts Institute of Technology

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Citation: Quantum simulators could help discover materials for high-performance electronics (October 30, 2024) https://phys.org/news/2024-10-quantum-simulator-uncover-materials-high Retrieved October 30, 2024 from .html

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