Anomalous topological Bloch oscillations under non-Abelian gauge fields

Trapped matter-wave interferometry offers the promise of compact high-precision local force sensing. However, noise in the trap itself can introduce new systematic errors which are absent in traditional free-fall interferometers. We describe and demonstrate an intrinsically noise-tolerant Floquet-engineered platform for continuously trapped atom interferometry. A non-interacting degenerate quantum gas undergoes position-space Bloch oscillations through an amplitude-modulated optical lattice, whose resulting Floquet-Bloch band structure includes Landau-Zener beamsplitters and Bragg mirrors, forming the components of a Mach-Zehnder interferometric force sensor. We identify, realize, and experimentally characterize magic band structures, analogous to the magic wavelengths employed in optical lattice clocks, for which the interferometric phase is insensitive to lattice intensity noise. We leverage the intrinsic programmability of the Floquet band synthesis approach to demonstrate a variety of interferometer structures, highlighting the potential of this technique for quantum force sensors which are tunable, compact, simple, and robust.

Recent experimental demonstration of the quantum coherent phase slip and current quantization in the superconductors, the fundamental phenomena dual to the coherent Cooper pair tunneling and voltage quantization (Shapiro steps), enables the development of a new quantum device, the Bloch transistor (BT). BT has a unique functionality: it can deliver quantized non-dissipative current to the quantum circuit. BT consists of two coupled Josephson Junctions (JJ) in the regime of coherent quantum phase slip. At the heart of the BT operation is a new mechanism for phase-locking the Bloch oscillations in JJs to microwaves via induced charge. The charge phase locking allows not only quantization of current but also gate voltage control of this quantization through the Aharonov-Casher effect. We study the operation of the BT and analyze its parameters. BT technology is scalable and compatible with other superconducting quantum devices, making it part of an emerging cryogenic quantum technology platform.

Pump–probe spectroscopy is a powerful tool for probing the response dynamics of quantum many-body systems in and out-of-equilibrium. Quantum computers have proved useful in simulating such experiments by exciting the system, evolving, and then measuring observables to first order, all in one setting. Here, we use this approach to investigate the mixed-field Ising model, where the longitudinal field plays the role of a confining potential that prohibits the spread of the excitations, spinons, or domain walls into space. We study the discrete bound states that arise from such a setting and their evolution under different quench dynamics by initially pumping the chain out of equilibrium and then probing various non-equal time correlation functions. Finally, we study false vacuum decay, where initially one expects unhindered propagation of the ground state, or true vacuum, bubbles into the lattice, but instead sees the emergence of Bloch oscillations that are directly the reason for the long-lived oscillations in this finite-size model. Our work sets the stage for simulating systems out-of-equilibrium on classical and quantum computers using pump–probe experiments without needing ancillary qubits.

We report theoretically polarization-controlled Bloch oscillations in the synthetic two-level photonic system, where the horizontal and vertical polarizations of light emulate pseudospin up and down. We synthesize a magnetic lattice in the light-crystal interaction process and demonstrate directional Bloch oscillations of polarized light, accompanied by the optical Zener tunneling. Within this framework, we study the directional Bloch oscillations with pure spin-up and spin-down, as well as mixing spin, carried by the fundamental Gaussian mode. Furthermore, our formulism can be extended to the higher-order framework, realizing the Bloch oscillation of the topological spin texture. These results show that the Bloch oscillation can be effectively controlled by the incident spin (polarization). We therefore anticipate that the presented framework for the Bloch oscillations can find potential applications. For example, it can be exploited as a polarization-related device for optical information processing.

Two-dimensional hexagonal materials such as transition metal dichalcogenides exhibit valley degrees of freedom, offering fascinating potential for valley-based quantum computing and optoelectronics. In nonlinear optics, the K and K’ valleys provide excitation resonances that can be used for ultrafast control of excitons, Bloch oscillations, and Floquet physics. Under intense laser fields, however, the role of coherent carrier dynamics away from the K/K’ valleys is largely unexplored. In this study, we observe quantum interferences in high harmonic generation from monolayer WS2 as laser fields drive electrons from the valleys across the full Brillouin zone. In the perturbative regime, interband resonances at the valleys enhance high harmonic generation through multi-photon excitations. In the strong-field regime, the high harmonic generation is sensitively controlled by quantum interferences of laser-field-driven electrons occupying various points in the Brillouin zone, including regions far from the K/K’ valleys. Our experimental observations are in strong agreement with quantum simulations, validating their interpretation. This work proposes new routes for harnessing laser-driven quantum interference in two-dimensional hexagonal systems and all-optical techniques to occupy and read-out electronic structures in the full Brillouin zone via strong-field nonlinear optics, advancing quantum technologies.

Exact dynamics and Bloch oscillations in a non-Hermitian zigzag Glauber–Fock lattice

Abstract Nanoporous graphene (NPG) has been previously fabricated by on-surface-self assembly in the form of arrays of ∼ 1 nm-wide graphene nanoribbons connected via molecular bridges in a two-dimensional crystal lattice (Moreno et al 2018 Science 360 199). It is predicted that NPG may, despite its molecular structure, work as electron waveguides that display e.g. Talbot wave interference. Here, we theoretically demonstrate how the electronic wave guidance may be controlled by using of electrical fields transverse to the ribbons; at low fields, point-injected currents display spatially periodic patterns along the ribbons, while high fields localize the injected current to single ribbons. This behavior constitutes an electronic version of optical breathing modes of Bloch oscillations, providing a simple mechanism for controlling the current patterns down to the molecular scale. The robustness of the self-repeating patterns under edge disorder demonstrates that the breathing modes of single-ribbon injections offer exciting opportunities for applications in nanoelectronics, molecular sensing, and quantum information processing.

Abstract We investigate the emission of a qubit weakly coupled to a one-band coupled-cavity array where, due to an engineered gradient in the cavity frequencies, photons are effectively accelerated by a synthetic force F. For strong F, a reversible emission described by an effective Jaynes-Cummings model occurs, causing a chiral time-periodic excitation of an extensive region of the array, either to the right or to left of the qubit depending on its frequency. For weak values of F instead, a complex non-Markovian decay with revivals shows up. This is reminiscent of dynamics induced by mirrors in standard waveguides, despite the absence of actual mirrors, and can be attributed to the finite width of the energy band which confine the motion of the emitted photon. In a suitable regime, the decay is well described by a delay differential equation formally analogous to the one governing the decay of an atom in a multi-mode cavity where the cavity length and time taken by a photon to travel between the two mirrors are now embodied by the amplitude and period of Bloch oscillations, respectively.

We aim to explore a more efficient way to simulate few-body dynamics on quantum computers. Instead of mapping the second quantization of the system Hamiltonian to qubit Pauli gate representation via the Jordan-Wigner transform, we propose to use the few-body Hamiltonian matrix under the state-vector basis representation, which is more economical on the required number of quantum registers. For a single-particle excitation state on a one-dimensional chain, Γ qubits can simulate N=2Γ number of sites, in comparison to N qubits for N sites via the Jordan-Wigner approach. A two-band diatomic tight-binding model is used to demonstrate the effectiveness of the state-vector basis representation. Both one-particle and two-particle quantum circuits are constructed, and some numerical tests on IBM hardware are presented.

Abstract The Bloch oscillations of Weyl fermionic wave packets in magnetized Weyl semimetal slabs under the influence of applied strain are investigated. We find that the surface Fermi arcs and bulk states in Weyl semimetal exhibit pronounced distinct Bloch oscillations that strongly depend on the crystal momentum. Interestingly, the oscillations of surface Fermi arcs are periodic which are affected by varying the strength of applied strain but are not influenced by the magnetization direction and geometric confinement of the system. However, the Bloch oscillations of the bulk states are affected by varying the magnetization direction, strength of the strain and the geometric confinement. Remarkably, Bloch-oscillating Weyl semimetals emit a comb-like spectrum of incommensurate frequencies, providing potential for high-frequency current generation and terahertz broadband amplifiers. In addition, the direct-current drift velocity shows negative differential conductivity, a hallmark of the Bloch oscillation regime.

Bloch oscillation and Landau-Zener tunneling of a periodically kicked Dirac particle

Bloch oscillations of a soliton in a one-dimensional quantum fluid

We propose an experimental setup to probe the interplay between the quantum superposition principle and gravitational time dilation arising from the mass-energy equivalence. It capitalizes on state-of-the-art atom interferometers that can keep atoms trapped in a superposition of heights in Earth's gravitational field for exceedingly long times, reaching the minute scale. Our proposal consists of adding two additional laser pulses to the existing experiments that would set up a clock trapped at a superposition of heights, reading a quantum superposition of relativistic proper times. We develop a method to include relativistic corrections to Bloch oscillations, which describe the trapped part of the interferometer. We derive the trajectories and corresponding phases acquired in each arm of the interferometer. We then show that a superposition of proper times manifests in the interference pattern in two ways: visibility modulations and a shift of the atom's resonant frequency. We argue that the latter might be observable with current technology.

Excited-state-induced decoherence in long-lived Bloch oscillation

We investigate the sensing capacity of non-equilibrium dynamics in quantum systems exhibiting Bloch oscillations. By focusing on the resource efficiency of the probe, quantified by quantum Fisher information, we find different scaling behaviors in two different phases, namely localized and extended. Our results provide a quantitative ansatz for quantum Fisher information in terms of time, probe size, and the number of excitations. In the long-time regime, the quantum Fisher information is a quadratic function of time, touching the Heisenberg limit. The system size scaling drastically depends on the phase changing from quantum-enhanced scaling in the extended phase to size-independent behavior in the localized phase. Furthermore, increasing the number of excitations always enhances the precision of the probe, although, in the interacting systems the enhancement becomes less eminent than the non-interacting probes. This is due to the induced localization by increasing the interaction between the excitations. We show that a simple particle configuration measurement together with a maximum likelihood estimation can closely reach the ultimate precision limit in both single- and multi-particle probes.

Bloch oscillations in interacting systems driven by a time-dependent magnetic field

Two kinds of multidimensional atom interferometers are demonstrated that are capable of measuring both the magnitude and direction of applied inertial forces. These interferometers, built from ultracold Bose-Einstein condensed rubidium atoms, use an original design that operates entirely within the Bloch bands of an optical lattice. Through time-dependent lattice position control, we realize Bloch oscillations in two dimensions and a vector atomic Michelson interferometer. Fits to the observed Bloch oscillations demonstrate the measurement of an applied acceleration of 2g along two axes, where g is Earth's gravitational acceleration. For the Michelson interferometer, we perform Bayesian inferencing from a 49-channel output by repeating experiments for two-axis accelerations and demonstrate vector parameter estimation. Accelerations can be measured from single experimental runs and do not require repeated shots to construct a fringe. The performance of our device is near the quantum limit for the interferometer size and quantum detection efficiency of the atoms.

We examine the effect of fractionality on the Bloch oscillations (BO) of a 1D tight-binding lattice when the discrete Laplacian is replaced by its fractional form. We obtain the eigenmodes and the dynamic propagation of an initially localized excitation in a closed form as a function of fractional exponent and the strength of the external potential. We find an oscillation period equal to that of the non-fractional case. The participation ratio is computed in a closed form, and it reveals that the localization of the modes increases with a deviation from the standard case and with an increase in the external constant field. When nonlinear effects are included, a competition between the tendency to Bloch oscillate and the trapping tendency typical of the Kerr effect is observed, which ultimately obliterates the BO in the limit of large nonlinearity.

Modulating number of Bloch oscillations in synthetic temporal lattices