Abstract Composed of some collective excited states of an atomic ensemble, a superradiance lattice can be considered as an infinite tight‐binding model in momentum space. In this work, a non‐Hermitian superradiance lattice is realized by introducing state‐selective dissipation rates, using room‐temperature atoms. The steady‐state response of such a non‐Hermitian momentum lattice is studied with non‐Hermitian absorption spectroscopy both theoretically and experimentally. A pit‐to‐peak transition in the spectroscopy is observed when the introduced dissipation rates are tuned. Further, by accounting for the thermal motion of atoms, the Wannier Stark ladders and biorthogonal Berry phases are measured. This work hence realizes a quantum platform that can be highly useful for future experimental simulation of non‐Hermitian physics (e.g., non‐Hermitian topological lattice) with room‐temperature atoms.
Abstract Composed of some collective excited states of an atomic ensemble, a superradiance lattice can be considered as an infinite tight‐binding model in momentum space. In this work, a non‐Hermitian superradiance lattice is realized by introducing state‐selective dissipation rates, using room‐temperature atoms. The steady‐state response of such a non‐Hermitian momentum lattice is studied with non‐Hermitian absorption spectroscopy both theoretically and experimentally. A pit‐to‐peak transition in the spectroscopy is observed when the introduced dissipation rates are tuned. Further, by accounting for the thermal motion of atoms, the Wannier Stark ladders and biorthogonal Berry phases are measured. This work hence realizes a quantum platform that can be highly useful for future experimental simulation of non‐Hermitian physics (e.g., non‐Hermitian topological lattice) with room‐temperature atoms.
Quantum simulation offers an analog approach for exploring exotic quantum phenomena using controllable platforms, typically necessitating ultracold temperatures to maintain the quantum coherence. Superradiance lattices (SLs) have been harnessed to simulate coherent topological physics at room temperature, but the thermal motion of atoms remains a notable challenge in accurately measuring the physical quantities. To overcome this obstacle, we implement a velocity scanning tomography technique to discern the responses of atoms with different velocities, allowing cold-atom spectroscopic resolution within room-temperature SLs. By comparing absorption spectra with and without atoms moving at specific velocities, we can derive the Wannier-Stark ladders of the SL across various effective static electric fields, their strengths being proportional to the atomic velocities. We extract the Zak phase of the SL by monitoring the ladder frequency shift as a function of the atomic velocity, effectively demonstrating the topological winding of the energy bands. Our research signifies the feasibility of room-temperature quantum simulation and facilitates their applications in quantum information processing.
Ultracold atoms provide a flexible platform for simulating topological phases. However, they are intrinsically prone to thermal noise, which can overwhelm topological response and hamper promised applications. On the other hand, topological invariants can be reconstructed from the energy spectra of particles subjected to a static force, based on the polarization relation between Wannier-Stark ladders and Zak phases. Such spectroscopic methods circumvent the obstacle to measuring topological invariants in thermal atoms. Here we reconstruct Zak phases from the anti-crossing between Wannier-Stark ladders in room-temperature superradiance lattices. Without dynamical manipulation routinely needed in ultracold atoms, we evaluate Zak phases directly from the absorption spectra. The thermal atomic motion, an essential source of noise in cold atoms, plays a key role in extracting Zak phases. Our approach paves the way of measuring topological invariants and developing their applications in room-temperature atoms.
Floquet modulation has been widely used in optical lattices for coherent control of quantum gases, in particular for synthesizing artificial gauge fields and simulating topological matters. However, such modulation induces heating which can overwhelm the signal of quantum dynamics in ultracold atoms. Here we report that the thermal motion, instead of being a noise source, provides a new control knob in Floquet-modulated superradiance lattices, which are momentum-space tight-binding lattices of collectively excited states of atoms. The Doppler shifts combined with Floquet modulation provide effective forces along arbitrary directions in a lattice in frequency and momentum dimensions. Dynamic localization, dynamic delocalization, and chiral edge currents can be simultaneously observed from a single transport spectrum of superradiance lattices in thermal atoms. Our Letter paves a way for simulating Floquet topological matters in room-temperature atoms and facilitates their applications in photonic devices.
Non-Hermitian physics exhibits unique physical properties beyond those of traditional Hermitian systems, such as symmetry breaking, the emergence of exceptional points, topological phase transitions, and more. These phenomena have been extensively studied across various platforms, including quantum optics, cold atom systems, superconducting circuits, and condensed matter physics. Rydberg atoms, with their long-range interactions and flexible controllability, provide a promising platform for the experimental realization of non-Hermitian physics. This review primarily summarizes the key experimental and theoretical achievements in the field of non-Hermitian physics within Rydberg atomic systems in recent years. It outlines the fundamental construction of non-Hermitian Hamiltonians, reveals the effective dissipation mechanisms induced by Rydberg atomic interactions, and discusses their impact on spectral properties and symmetry breaking. These studies not only deepen the understanding of quantum phase transitions in non-Hermitian many-body systems but also highlight the unique value of Rydberg atomic platforms in realizing and controlling topological states.
We investigate the dynamical lattice behavior of ultracold bosonic atoms loaded into an optical lattice with two-body dissipation. In the Mott insulating limit, the resulting system can emulate a variety of spin-1/2 non-Hermitian Heisenberg models such as the non-Hermitian Ising, XX, and XXZ models. These different spin models are implemented by tuning the parameter spaces of the hopping amplitude, the loss rates of atoms, and on-site interaction of strength. Moreover, utilizing the improved non-Hermitian density-matrix renormalization group (NH-DMRG) algorithm, we present the correlation functions, Bell nonlocality (B), and quantum Fisher information (QFI) of the non-Hermitian spin systems, where the QFI inversion and order-of-magnitude reduction demonstrate a high sensitivity to the non-Hermitian system parameters. In addition, there exists a parameter space where non-Hermitian and Hermitian systems exhibit the same phase transition behavior as indicated by QFI and B. Our results open a new avenue toward the quantum simulation and observation of non-Hermitian many-body systems.
Non-Hermitian physics exhibits unique physical properties beyond those of traditional Hermitian systems, such as symmetry breaking, the emergence of exceptional points, topological phase transitions, and more. These phenomena have been extensively studied across various platforms, including quantum optics, cold atom systems, superconducting circuits, and condensed matter physics. Rydberg atoms, with their long-range interactions and flexible controllability, provide a promising platform for the experimental realization of non-Hermitian physics. This review primarily summarizes the key experimental and theoretical achievements in the field of non-Hermitian physics within Rydberg atomic systems in recent years. It outlines the fundamental construction of non-Hermitian Hamiltonians, reveals the effective dissipation mechanisms induced by Rydberg atomic interactions, and discusses their impact on spectral properties and symmetry breaking. These studies not only deepen the understanding of quantum phase transitions in non-Hermitian many-body systems but also highlight the unique value of Rydberg atomic platforms in realizing and controlling topological states.