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We study the emergence of prethermal Floquet Time Crystal (pFTC) in disordered chiral multiferroic chains. The model is an extension of the usual periodically driven nearest-neighbor disordered Heisenberg chain, with additional next-nearest-neighbor Heisenberg couplings and DMI interactions due to external magnetic and electric couplings. We derive the phase diagram of the model, characterizing the magnetization, entanglement, and coherence dynamics of the system along the extended interactions. In addition, we explore the application of the pFTC as quantum sensors of AC fields. The sensor performance to estimate small AC fields is quantified through the quantum Fisher information (QFI) measure. The sensor offers several advantages as compared to those composed of non-interacting spins due to its intrinsic robustness, long coherent interrogation time, and many-body correlations. Specifically, the sensor can overcome the standard quantum limit ($\rm{SQL} \sim N t^2$) during the prethermal regime, reaching an optimum performance at the pFTC lifetime $t^*$, where the $\rm{QFI}/Nt^{*^2} \sim N^\alpha$ with $\alpha > 0$, scaling superlinarly with the number of spins. Different from \text{full} FTCs, the prethermal lifetime does not diverge in the thermodynamic limit, nevertheless it can be exponentially long with tuning system parameters., Comment: 9 pages, 5 figures

The dynamic region of out-of-time-ordered correlators (OTOCs) is a valuable discriminator of chaos in classical and semiclassical systems, as it captures the characteristic exponential growth. However, in spin systems, it does not reliably quantify chaos, exhibiting similar behavior in both integrable and chaotic systems. Instead, we leverage the saturation behavior of OTOCs as a means to differentiate between chaotic and integrable regimes. We use integrable and nonintegrable quenched field Floquet systems to describe this discriminator. In the integrable system, the saturation region of OTOCs exhibits oscillatory behavior, whereas, in the chaotic system, it shows exact saturation i.e., system gets thermalized. To gain a clearer understanding of the oscillations, we calculate the inverse participation ratio (IPR) for the normalized Fourier spectrum of OTOC. In order to further substantiate our findings, we propose the nearest-neighbor spacing distribution (NNSD) of time-dependent unitary operators. This distribution effectively differentiates chaotic and regular regions, corroborating the outcomes derived from the saturation behavior of OTOC., Comment: 12 Pages and 12 Figures

Scrambling of quantum information in both integrable and nonintegrable systems, including the transverse field Ising model (TFIM) and Floquet spin systems are studied. Our study employs tripartite mutual information (TMI), with negative TMI serving as an indicator of scrambling, where a more negative value suggests a higher degree of scrambling. In the integrable and nonintegrable TFIM, we observe pronounced scrambling behavior, with the initial growth following a power-law pattern. However, nonintegrable TFIM exhibits a higher degree of scrambling compared to the integrable version. In the Floquet system, TMI is studied across periods from $0$ to $\pi/2$. Both integrable and nonintegrable Floquet systems display scrambling behavior across all periods, except at $\tau=\pi/4$, featuring power-law growth for small periods and abrupt jumps for larger ones. Nonintegrable Floquet systems exhibit more pronounced scrambling compared to integrable ones across all periods. The degree of scrambling increases as we move towards $\tau = \pi/4$, reaching its peak near $\tau = \pi/4$ (but not at $\tau = \pi/4$), regardless of the initial states. TMI saturation fluctuates less in the Floquet system in comparison to the TFIM. The growth of scrambling in the Floquet system mirrors TFIM for small periods but exhibits notably faster growth for larger periods. For a small period, the degree of scrambling in a Floquet system is comparable to that in the TFIM, but it becomes significantly greater for larger periods., Comment: 11 pages, 49 figures

Exploiting the effect of nonreciprocal magnons in a system with no inversion symmetry, we propose a concept of a quantum information diode, {\it i.e.}, a device rectifying the amount of quantum information transmitted in the opposite directions. We control the asymmetric left and right quantum information currents through an applied external electric field and quantify it through the left and right out-of-time-ordered correlation (OTOC). To enhance the efficiency of the quantum information diode, we utilize a magnonic crystal. We excite magnons of different frequencies and let them propagate in opposite directions. Nonreciprocal magnons propagating in opposite directions have different dispersion relations. Magnons propagating in one direction match resonant conditions and scatter on gate magnons. Therefore, magnon flux in one direction is damped in the magnonic crystal leading to an asymmetric transport of quantum information in the quantum information diode. A quantum information diode can be fabricated from an yttrium iron garnet (YIG) film. This is an experimentally feasible concept and implies certain conditions: low temperature and small deviation from the equilibrium to exclude effects of phonons and magnon interactions. We show that rectification of the flaw of quantum information can be controlled efficiently by an external electric field and magnetoelectric effects., Comment: Accepted for publication in Materials for Quantum Technology

We study characteristic, dynamic, and saturation regimes of the out-of-time-order correlation (OTOC) in the constant field Floquet system with and without longitudinal field. In the calculation of OTOC, we take local spins in longitudinal and transverse directions as observables which are local and non-local in terms of Jordan-Wigner fermions, respectively. We use the exact analytical solution of OTOC for the integrable model (without longitudinal field term) with transverse direction spins as observables and numerical solutions for other integrable and nonintegrable cases. OTOCs generated in both cases depart from unity at a kick equal to the separation between the observables when the local spins in the transverse direction and one additional kick is required when the local spins in the longitudinal direction. The number of kicks required to depart from unity depends on the separation between the observables and is independent of the Floquet period and system size. In the dynamic region, OTOCs show power-law growth in both models, the integrable (without longitudinal field) as well as the nonintegrable (with longitudinal field). The exponent of the power-law increases with increasing separation between the observables. Near the saturation region, OTOCs grow linearly with a very small rate., Comment: 12 pages, 7 figures

Out-of-time-order correlators (OTOC) in the Ising Floquet system, that can be both integrable and nonintegrable is studied. Instead of localized spin observables, we study contiguous symmetric blocks of spins or random operators localized on these blocks as observables. We find only power-law growth of OTOC in both integrable and nonintegrable regimes. In the non-integrable regime, beyond the scrambling time, there is an exponential saturation of the OTOC to values consistent with random matrix theory. This motivates the use of "pre-scrambled" random block operators as observables. A pure exponential saturation of OTOC in both integrable and nonintegrable system is observed, without a scrambling phase. Averaging over random observables from the Gaussian unitary ensemble, the OTOC is found to be exactly same as the operator entanglement entropy, whose exponential saturation has been observed in previous studies of such spin-chains., Comment: 13 pages, 6 figures

We study the out-of-time-order correlation (OTOC) of the Floquet transverse Ising model and use it to verify the phase diagram of the system. First, we present the exact analytical solution of the transverse magnetization OTOC using the Jorden-Wigner transformation. We calculate the speed of correlation propagation and analyze the behavior of the revival time with the separation between the observables. In order to get the phase structure of the Floquet transverse Ising system, we use the longitudinal magnetization OTOC as it is known to serve as an order parameter of the system. We show the phase structure numerically in the transverse Ising Floquet system by using the long time average of the longitudinal magnetization OTOC. In both the open and the closed chain systems, we find distinct phases out of which two are paramagnetic (0-paramagnetic and $\pi$-paramagnetic), and two are ferromagnetic (0-ferromagnetic and $\pi$-ferromagnetic) as defined in the literature., Comment: 11 Pages, 8 Figures