Abstract Periodically driving a quantum many‐body system can drastically change its properties, leading to exotic non‐equilibrium states of matter without a static analog. In this scenario, parametric resonances and the complexity of an interacting many‐body system are pivotal in establishing non‐equilibrium states. A Floquet‐engineered transverse field Ising model for the controlled propagation in one dimension of spin waves is reported. The underlying mechanisms behind the proposal rely on high‐frequency drivings using characteristic parametric resonances of the spin lattice. Many‐body resonances modulating spin‐spin exchange or individual spin gaps inhibit interactions between spins thus proving a mechanism for controlling spin‐wave propagation and a quantum switch. The schemes may be implemented in circuit QED with direct applications in coupling–decoupling schemes for system‐reservoir interaction and routing in quantum networks.
Abstract Periodically driving a quantum many‐body system can drastically change its properties, leading to exotic non‐equilibrium states of matter without a static analog. In this scenario, parametric resonances and the complexity of an interacting many‐body system are pivotal in establishing non‐equilibrium states. A Floquet‐engineered transverse field Ising model for the controlled propagation in one dimension of spin waves is reported. The underlying mechanisms behind the proposal rely on high‐frequency drivings using characteristic parametric resonances of the spin lattice. Many‐body resonances modulating spin‐spin exchange or individual spin gaps inhibit interactions between spins thus proving a mechanism for controlling spin‐wave propagation and a quantum switch. The schemes may be implemented in circuit QED with direct applications in coupling–decoupling schemes for system‐reservoir interaction and routing in quantum networks.
Periodically driven systems, so-called Floquet systems, exhibit novel and exotic phases of matters inaccessible in static counterparts. The associated flexibility offered by Floquet engineering has helped gain insight into synthetic dimensions of quantum systems, non-equilibrium dynamics, and topology. Here, we apply the technique of Floquet engineering to the coherent dressing of spin states, aiming to provide a new dimension in the spin manipulation. We use an anti-relaxation coated 87 Rb vapor cell interacting with a transverse radio-frequency magnetic field, which is resonant with the Larmor precession and excites the coherence between adjacent Zeeman sublevels. The narrow linewidth of the natural resonance promises the successful observation of a radio-frequency dressed spin state via electromagnetically induced transparency spectroscopy. In this configuration, we create a Floquet system by adding a longitudinal oscillating magnetic field to periodically drive Zeeman levels. We experimentally observe the Floquet engineered coherent dressing spectroscopy, featuring a series of sidebands in frequency space with weight factor in terms of Bessel function, as expected by our theoretical model. Our method can be applied to coherent dressed states of natural and artificial atoms, offering the possibilities of quantum bit control and quantum sensing.
Abstract We report on the control of spin pair fluctuations using two-tone Floquet engineering. We consider a one-dimensional spin-1/2 lattice with periodically modulated spin exchanges using parametric resonances. The stroboscopic dynamics generated from distributed spin exchange modulations lead to spin pair fluctuations reaching quasi-maximally correlated states and a subharmonic response in local observables, breaking the discrete-time translational symmetry. We present a protocol to control the interacting many-body dynamics, producing spatial and temporal localization of correlated spin pairs via dynamically breaking correlated spin pairs from the edges towards the center of the lattice. Our result reveals how spin fluctuations distribute in a heterogeneous lattice depending on parametric resonances. This may open new routes for exploring distinct nonequilibrium states of matter and the conduction of quasiparticles in quantum materials.
Considering the example of superconducting circuits, we show how Floquet engineering can be combined with reservoir engineering for the controlled preparation of target states. Floquet engineering refers to the control of a quantum system by means of time-periodic forcing, typically in the high-frequency regime, so that the system is governed effectively by a time-independent Floquet Hamiltonian with novel interesting properties. Reservoir engineering, on the other hand, can be achieved in superconducting circuits by coupling a system of artificial atoms (or qubits) dispersively to pumped leaky cavities, so that the induced dissipation guides the system into a desired target state. It is not obvious that the two approaches can be combined, since reaching the dispersive regime, in which system and cavities exchange excitations only virtually, can be spoiled by driving-induced resonant transitions. However, working in the extended Floquet space and treating both system-cavity coupling as well as driving-induced excitation processes on the same footing perturbatively, we identify regimes, where reservoir engineering of targeted Floquet states is possible and accurately described by an effective time-independent master equation. We successfully benchmark our approach for the preparation of the ground state in a system of interacting bosons subjected to Floquet-engineered magnetic fields in different lattice geometries.
Abstract The capability to design spectrally controlled photon emission is not only fundamentally interesting for understanding frequency‐encoded light–matter interactions, but also is essential for realizing the preparation and manipulation of quantum states. Here, a dynamically modulated qubit array is considered, and realize frequency‐controlled single‐photon emission focusing on the generation of a frequency comb constituted solely of even‐parity or anti‐Stokes sidebands. This system also offers parity‐dependent bunching and antibunching in frequency‐filtered quantum correlations. In particular, the waveguide quantum electrodynamics (QED) setup is extended to include chiral and non‐local coupling architectures, thereby enhancing its versatility in Floquet engineering. This proposal also supports the predictable generation of high‐dimensional entangled quantum states, where the corresponding effective Hilbert space dimension is well controlled by energy modulation. Moreover, the utilisation of sophisticated numerical tools, such as the matrix product states (MPSs) and the discretization approach, enables the efficient simulation of multi‐photon dynamics, in which the non‐Markovian Floquet steady states emerge. This work fundamentally broadens the fields of collective emission, and has wide applications in implementing frequency‐encoded quantum information processing and many‐body quantum simulation.
We propose and analyze two distinct routes toward realizing interacting symmetry-protected topological (SPT) phases via periodic driving. First, we demonstrate that a driven transverse-field Ising model can be used to engineer complex interactions which enable the emulation of an equilibrium SPT phase. This phase remains stable only within a parametric time scale controlled by the driving frequency, beyond which its topological features break down. To overcome this issue, we consider an alternate route based upon realizing an intrinsically Floquet SPT phase that does not have any equilibrium analog. In both cases, we show that disorder, leading to many-body localization, prevents runaway heating and enables the observation of coherent quantum dynamics at high energy densities. Furthermore, we clarify the distinction between the equilibrium and Floquet SPT phases by identifying a unique micromotion-based entanglement spectrum signature of the latter. Finally, we propose a unifying implementation in a one-dimensional chain of Rydberg-dressed atoms and show that protected edge modes are observable on realistic experimental time scales.
Adiabatically varying the driving frequency of a periodically driven many-body quantum system can induce controlled transitions between resonant eigenstates of the time-averaged Hamiltonian, corresponding to adiabatic transitions in the Floquet spectrum and presenting a general tool in quantum many-body control. Using the central spin model as an application, we show how such controlled driving processes can lead to a polarization-based decoupling of the central spin from its decoherence-inducing environment at resonance. While it is generally impossible to obtain the exact Floquet Hamiltonian in driven interacting systems, we exploit the integrability of the central spin model to show how techniques from quantum quenches can be used to explicitly construct the Floquet Hamiltonian in a restricted many-body basis and model Floquet resonances.