Recently, ‘Quantum Materials’ has become a powerful umbrella concept. It has grown in popularity in various fields of science and technology, ranging from condensed matter and cold atom physics to materials science and quantum computing. Two upcoming publications have greatly marked this evolving concept of quantum materials. In both papers, the researchers described a strategy to achieve record levels of precision for simulating quantum materials.
In the first study, researchers looked at one-dimensional systems such as thin wires and demonstrated how to accurately calculate electrical parameters such as current and conductance. In the second article, the researchers show how to use a quantum processor to reproduce essential physical properties using the Fermi-Hubbard model of interacting electrons. These results represent a crucial step towards achieving the long-term goal of modeling more complex systems with real-world applications, such as batteries and drugs.
Calculation of the electronic properties of a quantum ring
In a forthcoming article titled ‘Accurately calculate the electronic properties of a quantum ring‘, the researchers described how to calculate the specific electrical properties of quantum materials. The article focuses on one-dimensional conductors, which the researchers model using the Sycamore processor to create an 18-qubit loop that mimics a thin wire.
The researchers demonstrated the underlying physics with a series of simple textbook experiments, starting with calculating the band structure of the wire that describes the link between electronic energy and speed. They got less than one percent of the error, despite an 18-qubit algorithm with over 1,400 logic operations. This was a primary computational task for short-term devices.
In general, Quantum processors must overcome two critical sources of error to outperform conventional approaches: control error and decoherence. The researchers presented an experimental design to obtain a low control error and complete decoherence. The robust characteristics of the Fourier transform allowed for this level of precision.
The researchers measured a quantum signal that oscillates over time with a small number of frequencies. A Fourier transform of the signal showed peaks at the oscillation frequencies. While the experimental flaws have an impact on the height of the observed peaks, the center frequencies remain unchanged. On the other hand, the researchers found that the center frequencies were particularly sensitive to the physical attributes of the cord. The idea of the study was to examine quantum Fourier signals that provide robust protection against experimental errors while giving the underlying quantum system a sensitive probe.
The Fermi-Hubbard model
In the newspaper ‘Observation of separate charge and spin dynamics in the Fermi-Hubbard modelThe researchers examined the dynamic behavior of electrons as they interact in the Fermi-Hubbard model. In some regimes, the model is extremely difficult to solve on traditional computers and is commonly used to test numerical approaches for tightly correlated systems. Spin-charge separation, or the fact that spin and charge excitations move at different speeds due to interparticle interactions, is a unique property of the one-dimensional Fermi-Hubbard model.
When the particles interact, new spontaneous phenomena like high temperature superconductivity and spin charge separation are produced. The Fermi-Hubbard model can easily represent this behavior. Atomic nuclei in materials like metals create a crystal lattice, and electrons bounce from one lattice site to another, carrying an electric current. It is essential to include the repulsion that electrons experience as they come close to each other to describe these systems appropriately. The Fermi-Hubbard model describes this physics with two simple parameters: the jump rate (J) and the repulsion intensity (U).
Researchers could update the dynamics of the model by mapping the two physical parameters to logical operations on the processor qubits. They simulated an electronic state in which electronic charge and spin densities peak around the center of the qubit lattice using these methods. The high connections between electrons cause charge and spin densities to propagate at different speeds as the system evolves. Their results gave a clear picture of the interacting electrons and served as a benchmark for modeling quantum materials using superconducting qubits.
Quantum processors have the potential to tackle difficult computational tasks faster than traditional methods. However, these built platforms must offer computational precision beyond current traditional approaches to be seen as real challenges. Therefore, these two experiments demonstrate an astonishing level of precision in the simulation of simple materials. The researchers hope that these experimental results will help move beyond the classical computing age.
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