A research team led by The Hong Kong University of Science and Technology (HKUST) has achieved a groundbreaking quantum simulation of the non-Hermitian skin effect in two dimensions using ultracold fermions, marking a significant advance in quantum physics research.
Quantum mechanics, which typically considers a well-isolated system from its environment, describes ubiquitous phenomena ranging from electron behavior in solids to information processing in quantum devices. This description typically requires a real-valued observable—specifically, a Hermitian model (Hamiltonian).
The Hermiticity of the model, which guarantees conserved energy with real eigenvalues, breaks down when a quantum system exchanges particles and energy with its environment. Such an open quantum system can be effectively described by a non-Hermitian Hamiltonian, providing crucial insights into quantum information processing, curved space, non-trivial topological phases, and even black holes. Nevertheless, many questions about non-Hermitian quantum dynamics remain unanswered, especially in higher dimensions.
In collaboration with Peking University (PKU), physicists from the two universities have simulated one such intriguing phenomenon—the non-Hermitian skin effect (NHSE)—which involves the accumulation of eigenstates at the boundary of an open system. This successful demonstration marks a crucial advancement, as previous experimental realizations of the non-Hermitian skin effect were limited to lower dimensions or classical systems rather than quantum systems.
This finding is published in Nature on January 8, 2025. The research created a two-dimensional non-Hermitian topological band for ultracold fermions in spin-orbit-coupled optical lattices with tunable dissipation, unveiling the non-Hermitian skin effect, says Prof. JO Gyu-Boong , Professor of Physics at HKUST leading the study.
"Our work unveils an intriguing system that allows us to explore how non-Hermiticity plays with symmetry and topology," said Prof. Jo. "Our experiment naturally sets a quantum many-body system instead of classical systems, opening up avenues to investigate non-Hermitian quantum dynamics using ultracold fermions with dissipation."
Prof. LIU Xiong-jun, Professor at PKU and the other leader of the team added, "The interplay of higher-dimensional non-Hermitian skin effect with fundamental Hermitian scenarios, such as curved spaces, black holes, quantum information, and higher-order topological phases, necessitates exploration in many-body systems beyond a one-dimensional system. The high degree of control in our system positions it as a versatile platform for exploring high-dimensional non-Hermitian phenomena, offering insights into exotic quantum physics beyond the realms of condensed matter and ultracold atoms."
The team emphasized that a complete understanding of the NHSE remains elusive, with key questions still unanswered: "Is there a general topological explanation for NHSE?" and "How much does topology determine its presence or absence?" "This reported work sets the stage for exploring such questions," Prof. Jo added.
Nature
Experimental study
Not applicable
Two-dimensional non-Hermitian skin effect in an ultracold Fermi gas
8-Jan-2025