The Rice−Mele model has been a seminal prototypical model for the study of topological phenomena such as Thouless pumping. Here we implement the interacting Rice−Mele model using a superconducting quantum processor comprising a one-dimensional array of 36 qutrits. By adiabatically cycling the qutrit frequencies and hopping strengths in the parametric space, we emulate the Thouless pumping of single and two bounded microwave photons along the qutrit chain. Furthermore, with strong Hubbard interaction inherent in the qutrits we also emulate the intriguing phenomena of resonant tunneling and asymmetric edge-state transport of two interacting photons. Utilizing the interactions and higher energy levels in such fully controlled synthetic quantum simulators, these results demonstrate new opportunities for exploring exotic topological phases and quantum transport phenomena using superconducting quantum circuits.
The Rice−Mele model has been a seminal prototypical model for the study of topological phenomena such as Thouless pumping. Here we implement the interacting Rice−Mele model using a superconducting quantum processor comprising a one-dimensional array of 36 qutrits. By adiabatically cycling the qutrit frequencies and hopping strengths in the parametric space, we emulate the Thouless pumping of single and two bounded microwave photons along the qutrit chain. Furthermore, with strong Hubbard interaction inherent in the qutrits we also emulate the intriguing phenomena of resonant tunneling and asymmetric edge-state transport of two interacting photons. Utilizing the interactions and higher energy levels in such fully controlled synthetic quantum simulators, these results demonstrate new opportunities for exploring exotic topological phases and quantum transport phenomena using superconducting quantum circuits.
As the basis for generating multi-particle quantum correlations, inter-particle interaction plays a crucial role in collective quantum phenomena, quantum phase transitions, and quantum information processing. It can profoundly alter the band structure of quantum many-body systems and give rise to exotic topological phenomena. Conventional topological pumping, which has been well demonstrated in driven linear or noninteracting systems, may break down in the presence of strong interaction. However, the interplay between band topology and interaction could also induce emergent topological pumping of interacting particles, but its experimental realization has proven challenging. Here we demonstrate interaction-induced topological pumping in a solid-state quantum system comprising an array of 36 superconducting qubits. With strong interaction inherent in the qubits and site-resolved controllability of the lattice potential and hopping strength, we realize the topological Thouless pumping of single and two bounded particles. Beyond these topological phenomena with linear or noninteracting counterparts, we also observe topologically resonant tunneling and asymmetric edge-state transport of interacting particles. Our work creates a paradigm for multi-particle topological effects, and provides a new pathway to the study of exotic topological phenomena, many-body quantum transport, and quantum information transfer.
Topological insulators have inspired the study with various quantum simulators. Exploiting the tunability of the qubit frequency and qubit-qubit coupling, we show that a superconducting qubit chain can simulate various topological band models. When the system is restricted to the single-spin excitation subspace, the Su-Schrieffer-Heeger (SSH) model can be equivalently simulated by alternating the coupling strength between neighboring qubits. The existence of topological edge states in this qubit chain is demonstrated in the quench dynamics after the first qubit is excited. This excitation propagates along the chain where the qubit-qubit coupling is homogeneous. In contrast, in our qubit chain, the spin-up state localizes at the first qubit and the rest qubits remain in the spin-down state. We further show that the spin-up state can be transported along the chain by modulating the coupling strengths and the qubit frequencies. This demonstrates adiabatic pumping based on the Rice-Mele model. Moreover, we also discuss possible ways to construct other topological models with different topological phenomena within the current technology of superconducting qubits.
Topological phases are robust against weak perturbations, but break down when disorder becomes sufficiently strong. However, moderate disorder can also induce topologically nontrivial phases. Thouless pumping, as a (1+1)D counterpart of the integer quantum Hall effect, is one of the simplest manifestations of topology. Here, we report experimental observations of the competition and interplay between Thouless pumping and disorder on a 41-qubit superconducting quantum processor. We improve a Floquet engineering technique to realize cycles of adiabatic pumping by simultaneously varying the on-site potentials and the hopping couplings. We demonstrate Thouless pumping in the presence of disorder and show its breakdown as the strength of disorder increases. Moreover, we observe two types of topological pumping that are induced by on-site potential disorder and hopping disorder, respectively. In particular, an intrinsic topological pump that is induced by quasi-periodic hopping disorder has never been experimentally realized before. Our highly controllable system provides a valuable quantum simulating platform for studying various aspects of topological physics in the presence of disorder.
Abstract Localized edge modes provide a compact channel for transferring an excitation through an extended lattice, but the relation between the microscopic chain and the few levels that actually govern the transfer is often left implicit. We develop this boundary-subspace description for a superconducting-qubit realization of the Rice–Mele model in the single-excitation sector. For one finite chain, projection onto the two edge modes yields a Landau–Zener Hamiltonian whose detuning and hybridization identify the adiabatic transfer path and the spectral constraint relevant to protocol optimization. We then join two Rice–Mele segments at a single physical boundary qubit. The resulting three localized modes form an effective three-state channel with microscopically determined, independently tunable energies and couplings. This channel supports both a zero-energy dark-state passage and an open Rice–Mele-type passage driven by time-dependent bonds and onsite potentials. Direct simulations of the complete qubit chains reproduce the effective-channel dynamics. Under matched control bounds, dividing the transport distance at a shared boundary also preserves larger finite-size edge-mode couplings and reaches a stable high-fidelity regime faster than transfer through one uninterrupted chain. The boundary-mode projection thus relates the microscopic controls directly to the effective energies, finite-size couplings, and adiabatic gaps that govern the transfer.
Superconducting circuits have emerged as a powerful platform of quantum simulation, especially for emulating the dynamics of quantum many-body systems, because of their tunable interaction, long coherence time, and high-precision control. Here in experiments, we construct a Bose-Hubbard ladder with a ladder array of 20 qubits on a 24-qubit superconducting processor. We investigate theoretically and demonstrate experimentally the dynamics of single- and double-excitation states with distinct behaviors, indicating the uniqueness of the Bose-Hubbard ladder. We observe the linear propagation of photons in the single-excitation case, satisfying the Lieb-Robinson bounds. The double-excitation state, initially placed at the edge, localizes; while placed in the bulk, it splits into two single-excitation modes spreading linearly toward two boundaries, respectively. Remarkably, these phenomena, studied both theoretically and numerically as unique properties of the Bose-Hubbard ladder, are represented coherently by pairs of controllable qubits in experiments. Our results show that collective excitations, as a single mode, are not free. This work paves the way to simulation of exotic logic particles by subtly encoding physical qubits and exploration of rich physics by superconducting circuits.
Fluxonium superconducting circuits were originally proposed to realize highly coherent qubits. In this work, we explore how these circuits can be used to implement and harness qutrits, by tuning their energy levels and matrix elements via an external flux bias. In particular, we investigate the distinctive features of arrays of fluxonium qutrits, and their potential for the quantum simulation of exotic quantum matter. We identify four different operational regimes, classified according to the plasmon-like versus fluxon-like nature of the qutrit excitations. Highly tunable on-site interactions are complemented by correlated single-particle hopping, pair hopping and non-local interactions, which naturally emerge and have different weights in the four regimes. Dispersive corrections and decoherence are also analyzed. We investigate the rich ground-state phase diagram of qutrit arrays and propose practical dynamical experiments to probe the different regimes. Altogether, fluxonium qutrit arrays emerge as a versatile and experimentally accessible platform to explore strongly correlated bosonic matter beyond the Bose-Hubbard paradigm, and with a potential toward simulating lattice gauge theories and non-Abelian topological states.