Drainage, in which a nonwetting fluid displaces a wetting fluid from a porous medium, is well studied for media with unchanging solid surfaces. However, many media can be eroded by drainage, with eroded material redeposited in pores downstream, altering further flow. Here we use theory and simulation to examine how these coupled processes both alter the overall fluid displacement pathway and help reshape the solid medium. We find two drainage behaviors with markedly different characteristics and quantitatively delineate the conditions under which they arise. Our results thereby help expand the current understanding of these rich physics, with implications for applications of drainage in industry and the environment.

Long-lived ionic quantum states known as metastable electronic states in highly charged ions (HCIs) are of great interest in fundamental physics. Especially, it generates transitions with very narrow natural linewidth, which is a promising candidate for use in the next-generation HCI atomic clocks to reach an accuracy below ${10}^{-19}$. A recent experiment [Nature (London) 581, 42 (2020)] used Penning trap mass spectrometry to measure the energy of an extremely long-lived metastable electronic state, thus opening doors to search for HCI clock transitions. Building upon prior research, this study introduces an experimental proposal with the goal of measuring lifetimes of the metastable states beyond seconds. Our approach employs a sequential pulse-and-phase measurement scheme, allowing for direct observations of the decay processes from metastable electronic states through single-ion mass spectrometry in a Penning trap. This measurement poses a significant challenge to conventional techniques like fluorescence detection. To demonstrate the effectiveness of this method, we conducted a comprehensive simulation under real experimental conditions, yielding promising results in a specific scenario. Two suitable candidates are proposed for testing this method, and the state-of-the-art MCDHF theory are employed for accurate energy levels and transition rate calculations. Some future prospects in the experimental determinations of a wide range of energy and lifetimes of long-lived metastable electronic states, probing hyperfine and magnetic quenching effects on high-order forbidden transitions and search for high-quality HCI clock transitions are discussed.

Here we explore the possibility of precise time keeping in quantum systems using athermal resources. We show that quantum measurement engineered reservoirs can be used as athermal resources to drive the ticks of a quantum clock. Two- and three-level quantum systems act as transducers in our model, converting the quantum measurement-induced noise to produce a series of ticks. The ticking rate of the clock is maximized when the measured observable maximally noncommutes with the clock's Hamiltonian. We use the large deviation principle to characterize the statistics of observed ticks within a given time period and show that it can be sub-Poissonian—quantified by Mandel's Q parameter—alluding to the quantum nature of the clock. We discuss the accuracy and efficiency of the clock, and extend our framework to include hybrid quantum clocks fueled by both measurements, and thermal resources. We make comparisons to relatable recent proposals for quantum clocks, and discuss alternate device implementations harvesting the quantum measurement engineered nonequilibrium conditions, beyond the clock realization.

The Dzyaloshinskii-Moriya interaction (DMI), which is the antisymmetric part of the exchange interaction between neighboring local spins, winds the spin manifold and can stabilize nontrivial topological spin textures. Since topology is a robust information carrier, characterization techniques that can extract the DMI magnitude are important for the discovery and optimization of spintronic materials. Existing experimental techniques for quantitative determination of DMI, such as high-resolution magnetic imaging of spin textures and measurement of magnon or transport properties, are time-consuming and require specialized instrumentation. Here we show that a convolutional neural network can extract the DMI magnitude from minor hysteresis loops, or magnetic “fingerprints,” of a material. These hysteresis loops are readily available by conventional magnetometry measurements. This provides a convenient tool to investigate topological spin textures for next-generation information processing.

The nematicity in multilayer $\mathrm{FeSe}/{\mathrm{SrTiO}}_3$ films has been previously suggested to be enhanced with decreasing film thickness. Motivated by this, there have been many discussions about the competing relation between nematicity and superconductivity. However, the criterion for determining the nematicity strength in FeSe remains highly debated. The understanding of nematicity as well as its relation to superconductivity in FeSe films is therefore still controversial. Here, we fabricate multilayer $\mathrm{FeSe}/{\mathrm{SrTiO}}_3$ films using molecular beam epitaxy and study the nematic properties by combining angle-resolved photoemission spectroscopy, ${}^{77}\mathrm{Se}$ nuclear magnetic resonance, and scanning tunneling microscopy experiments. We unambiguously demonstrate that, near the interface, the nematic order is suppressed by the ${\mathrm{SrTiO}}_3$-induced tensile strain; in the bulk region further away from the interface, the strength of nematicity recovers to the bulk value. Our results not only solve the recent controversy about the nematicity in multilayer FeSe films, but also offer valuable insights into the relationship between nematicity and superconductivity.

Efimov effect is characterized by an infinite number of three-body bound states following a universal geometric scaling law at two-body resonances. In this paper, we investigate the influence of two-body losses which can be described by a complex scattering length $a_c$ on these states. Interestingly, the non-Hermiticity allows the system to have three-body bound states of energies with nonvanishing imaginary parts and real parts that may exceed the three-body or the atom-dimer scattering threshold. By taking the ${}^{133}\mathrm{Cs}\text{−}{}^{133}\mathrm{Cs}\text{−}{}^6\mathrm{Li}$ system as a concrete example, we calculate the trimer energies by solving the generalized Skorniakov–Ter-Martirosian equation and find such three-body bound states with energies that have positive real parts and obey a generalized geometric scaling law. Remarkably, we also find that in some regions these three-body bound states have longer lifetimes compared with the corresponding two-body bound states. In the absence of other loss mechanisms such as three-atom loss, the lifetimes for these trimer states can tend to infinity. Our work paves the way for the future exploration of few-body bound states in the complex plane.

We investigate ratcheting heat flow in simple networks consisting of a one-dimensional nonlinear chain with a self-coupled loop when the average thermal bias is zero. The effects of coupling strength and temporally averaged environmental reference temperature on the ratcheting heat flow are discussed. It is found that the total heat flow (THF) will be reversed, while heat flow in the self-coupled loop will disappear with the increase of the coupling strength. A critical coupling strength exists at which the THF disappears, and heat flow exists in the self-coupled loop, i.e., eddy ratcheting heat flow displays. The underlining physical mechanisms are analyzed through phonon spectra and unsteady thermal wave dynamics. Furthermore, a reversal of the THF from a negative to a positive value can be controlled by increasing the reference temperature. A critical reference temperature exists at which the negative THF exhibits a maximum value. Phonons dominate the ratcheting heat flow in the self-coupled loop, while solitons dominate the THF for weak coupling strength. These results can possibly be realized in nanoscale experiments and will help to further understand the thermal information on coupled nanotubes, polymer chains, and biological networks.

We analyze a new class of time-periodic nonreciprocal dynamics in interacting chaotic classical spin systems, whose equations of motion are conservative (phase-space-volume-preserving) yet possess no symplectic structure. As a result, the dynamics of the system cannot be derived from any time-dependent Hamiltonian. In the high-frequency limit, we find that the magnetization dynamics features a long-lived metastable plateau, whose duration is controlled by the fourth power of the drive frequency. However, due to the lack of an effective Hamiltonian, the prethermal state the system evolves into cannot be understood within the framework of the canonical ensemble. We propose a Hamiltonian extension of the system using auxiliary degrees of freedom, in which the original spins constitute an open yet nondissipative subsystem. This allows us to perturbatively derive effective equations of motion that manifestly display symplecticity breaking at leading order in the inverse frequency. We thus extend the notion of prethermal dynamics, observed in the high-frequency limit of periodically driven systems, to nonreciprocal systems.

We construct and analyze a lattice generalization of the Yukawa-Sachdev-Ye-Kitaev model, where spinful fermions experience onsite, random, all-to-all interactions with an Einstein bosonic mode, and random intersite coherent hopping. We obtain the exact self-consistent numerical solution of the model at mean-field level, and analytical approximations, for all values of fermion-boson coupling and hopping, under the spin-singlet ansatz and at particle-hole symmetry, both in the normal and superconducting states, thus tracing the entire phase diagram. In the normal state, the competition between hopping and coupling leads to crossovers between Fermi-liquid and non-Fermi-liquid states, as reflected by the fermionic and bosonic spectral functions and the normal-state entropy. We calculate the finite phase stiffness of the superconducting state through the equilibrium electromagnetic response. Furthermore, we study the critical temperature $T_c$, as well as the spectral functions, the quasiparticle weight, the gap, and the condensation energy in the superconducting state. At weak coupling, we retrieve a disordered generalization of Bardeen-Cooper-Schrieffer theory. At strong coupling, asymptotically $T_c$ saturates but the stiffness decreases, which suggests strong superconducting fluctuations. $T_c$ is maximum in the single-dot limit, while the stiffness peaks exactly at the crossover between non-Fermi-liquid and Fermi-liquid phases. We discover that the quasiparticle weight, the stiffness, and the condensation energy, are all correlated as a function of coupling, reminiscent of the correlations observed in high-temperature cuprate superconductors.

Variational quantum algorithms (VQAs) provide a promising approach to achieving quantum advantage for practical problems on near-term noisy intermediate-scale quantum (NISQ) devices. Thus far, most studies on VQAs have focused on qubit-based systems, but the power of VQAs can be potentially boosted by exploiting infinite-dimensional continuous-variable (CV) systems. Here, we implement the CV version of one VQA, a quantum approximate optimization algorithm, by developing an automated collaborative computing system between a programmable photonic quantum computer and a classical computer. We experimentally demonstrate that this algorithm solves the minimization problem of simple continuous functions by implementing the quantum version of gradient descent to localize an initially broadly distributed wave function to the minimum. This method allows the execution of a practical CV quantum algorithm on a physical platform. Our work can be extended to the minimization of more general functions, providing an alternative to achieve the quantum advantage in practical problems.

In open quantum systems, topological edge states rapidly lose coherence, making them unsuitable for topological quantum computation and quantum memory. In this study, we demonstrate that topologically non-Hermitian Liouville-Majorana edge modes (LMEMs) can persist in the extended Liouville-Fock space (LFS) of dissipative quantum spin or fermionic systems. This finding extends the scope of topological modes beyond typical Hermitian systems. By vectorizing the Lindblad equation of a dissipative Ising-type spin system using third quantization, we prove that it can be reduced to a series of non-Hermitian Kitaev chains in the extended LFS and that topologically protected LMEMs emerge due to internal symmetry. Furthermore, we present an explicit method for detecting these modes and demonstrate that the purity of the density matrix characterizes the long-range correlation of LMEMs. Our work offers a new direction for identifying stable topological states in open quantum systems induced by quantum jumps.

We demonstrate a digitally controlled piezoelectric metamaterial waveguide leveraging resonant, spatiotem-porally modulated synthetic impedance circuits for programmable reciprocity breaking. Piezoelectric metamaterials have effective stiffness that depends on the shunt circuitry connected to each unit cell, offering greatly increased design freedom over their purely mechanical counterparts. By connecting a digitally controlled synthetic impedance shunt circuit to each unit cell of the metamaterial domain, the effective stiffness is externally programmed according to a desired profile in space and time. Specifically, we present threefold capabilities in this electromechanical system: (1) smooth parameter modulation (no abrupt switching) through synthetic impedance circuits that eliminate cumbersome analog electrical components, (2) resonant electromechanical modulation in space and time so that one does not have to operate near the Bragg band gap, and (3) precise digital programming by numerically entering the space and time properties of the domain. We also demonstrate the frequency conversion in narrow-band excitation centered at a directional band gap. The experimental results are compared against high-fidelity multiphysics finite-element simulations, yielding excellent agreement for this class of digitally programmable nonreciprocal elastic metamaterials.

We propose a model-based reinforcement learning (RL) approach for noisy time-dependent gate optimization with reduced sample complexity over model-free RL. Sample complexity is defined as the number of controller interactions with the physical system. Leveraging an inductive bias, inspired by recent advances in neural ordinary differential equations (ODEs), we use an autodifferentiable ODE, parametrized by a learnable Hamiltonian ansatz, to represent the model approximating the environment, whose time-dependent part, including the control, is fully known. Control alongside Hamiltonian learning of continuous time-independent parameters is addressed through interactions with the system. We demonstrate an order of magnitude advantage in sample complexity of our method over standard model-free RL in preparing some standard unitary gates with closed and open system dynamics, in realistic computational experiments incorporating single-shot measurements, arbitrary Hilbert space truncations, and uncertainty in Hamiltonian parameters. Also, the learned Hamiltonian can be leveraged by existing control methods like GRAPE (gradient ascent pulse engineering) for further gradient-based optimization with the controllers found by RL as initializations. Our algorithm, which we apply to nitrogen vacancy (NV) centers and transmons, is well suited for controlling partially characterized one- and two-qubit systems.

The reproducibility of qubit parameters is a challenge for scaling up superconducting quantum processors. Signal cross talk imposes constraints on the frequency separation between neighboring qubits. The frequency uncertainty of transmon qubits arising from the fabrication process is attributed to deviations in the Josephson junction area, tunnel barrier thickness, and the qubit shunt capacitor. We decrease the sensitivity to these variations by fabricating larger Josephson junctions and reduce the wafer-level standard deviation in resistance down to 2%. We characterize 32 identical transmon qubits and demonstrate the reproducibility of the qubit frequencies with a 40 MHz standard deviation (i.e., 1%) with qubit quality factors exceeding 2 million. We perform two-level-system (TLS) spectroscopy and observe no significant increase in the number of TLSs causing qubit relaxation. We further show by simulation that for our parametric-gate architecture, and accounting only for errors caused by the uncertainty of the qubit frequency, we can scale up to 100 qubits with an average of only three collisions between quantum-gate transition frequencies, assuming $2\%$ cross talk and $99.9\%$ target gate fidelity.