Caloric cooling offers a promising solid-state alternative to conventional refrigeration. A traditional strategy to enhance cooling performance is increasing disorder-related configurational entropy change, which is a phenomenological approach and sometimes fails. Here, we establish a unified phonon-entropy framework applicable to electrocaloric, magnetocaloric, and mechanocaloric systems. By deriving analytical expressions that link entropy to the phonon density of states and mode-specific entropy, we enable mode-level tuning of caloric performance. Under this framework, we propose three key criteria for high-performance mechanocaloric cooling: high low-frequency phonon density of states, large changes in the product of density of states and mode-specific entropy, and low Young’s modulus. Accordingly, we identify PbO as a superior mechanocaloric material, which exhibits a pressure-induced entropy change nearly 2.7 times greater than TiNi, currently among the best-performing mechanocaloric materials. These findings establish a quantitative framework for phonon-entropy-driven caloric cooling and open other avenues for materials design.

Electrons bound to the surface of liquid helium are an emerging quantum computing platform, offering the potential for highly mobile spin qubits that can be manipulated using complementary metal-oxide-semiconductor (CMOS)-fabricated devices. Here, as a step toward realizing this technology, we demonstrate selective two-dimensional shuttling of electrons across a helium film condensed on the surface of a CMOS control chip. The electrons are moved in packets containing, on average, several tens down to single electrons. We perform CCD-style electron shuttling in any of 128 transport microchannels, each of which links electron storage zones and sensing zones in the two-dimensional plane. This shuttling “unit cell” is repeated 32 times across the chip, allowing packet sensing to be performed in parallel. Despite the resulting gain in sensitivity, we find no evidence of electron loss after repeating shuttling sequences at least ${10}^9$ times. The device serves as a prototype quantum information processing platform that is readily scalable to control large monolithically integrated arrays of electron spins.

We propose a scalable dual-species fluxonium-transmon system that utilizes a central transmon to mediate high-fidelity gates and parity checks between two fluxonium qubits without the need for strong nonlocal interactions. This approach suppresses unwanted long-range interactions, which is critical for developing larger quantum processors. First, we analyze the performance of cross-resonance (CR) cnot gates between a fluxonium and a transmon. We show that even in the presence of a spectator qubit, these gates maintain high fidelity with coherent errors on the order of ${10}^{-5}$. We then demonstrate that these gates, when applied sequentially, enable high-fidelity parity checks and logical fluxonium-fluxonium cnot gates. In addition, the central transmon can facilitate the readout of the neighboring fluxoniums, consolidating multiple critical functions into a single ancilla. Our work establishes the viability of a dual-species architecture as a promising path toward fault-tolerant quantum computation.

The surface of three-dimensional topological insulators (TIs) constitutes an intriguing system for hosting Majorana zero modes (MZMs) when rendered superconducting via the proximity effect. To study the peculiar role of MZMs and the accompanied $4\pi$-periodic energy-phase relation in TI-based Josephson junctions (JJs), we constructed a superconducting flux qubit out of a JJ based on ${\text{Sn}}_{0.02}{\text{Bi}}_{1.08}{\text{Sb}}_{0.9}{\text{Te}}_2\mathrm{S}$ (Sn-doped BSTS). In the vicinity of the qubit’s sweet spot, we obtained a two-tone spectrum that differed from that of a conventional flux qubit. The analysis employing different models suggests the existence of 4π-periodic supercurrents in the junction. The results support the fact that superconducting flux qubits incorporating TI-based JJs may serve as a potential platform for the detection and further braiding of MZMs.

The precise measurement of spatial attitude parameters is critical for applications in inertial navigation, industrial monitoring, instrument calibration, and quantum metrology. In this work, we theoretically investigate and experimentally realize the simultaneous measurement of the yaw and pitch angles using a Hermite-Gaussian-postselected double weak-value system integrated with two sets of high-order-mode balanced homodyne detections, thereby achieving a complete characterization of the beam deflection. Signals of the yaw and pitch angles that are involved in ${\text{TEM}}_{10}$ and ${\text{TEM}}_{01}$ modes output from two dark ports of the system can be measured independently. As a result, the obtained minimum measurable yaw and pitch angles of beam deflection are 83 and 89 prad, respectively. This work expands the beam-deflection measurement to two dimensions, providing new insights for future high-precision multiparameter spatial precise detection.

Dynamic atom gravimeters enable absolute gravity measurements on moving platforms. However, their performance is severely degraded due to the complex dynamic environment. This paper finds that the amplitude-modulation noise (AMN) is a key factor contributing to the degradation of gravity- measurement performance. We find that the AMN is induced by the cold atomic cloud trajectory and velocity variation. We build a model to illustrate the principles and magnitude of AMN arising from various experiment processes. Then we propose a method to fit the normalized AMN with respect to the kinematic parameters of the cold atomic cloud and successfully suppress this noise from 0.11 to 0.038 using the fitting result. With this method, we improve the fringe phase resolution from 0.244 to 0.092 rad and reduce the dynamic gravity-measurement noise from 2.69 to 1.68 mGal. This study finds and suppresses a key noise source in dynamic atom gravimeters, which is useful for further improving their precision. The proposed method can also be applied for precision enhancement for other dynamic atom-interferometer-based sensors, such as atom gradiometers and gyroscopes.

The properties of quantum dot–based spin qubits have significant interdevice variability due to the unavoidable presence of various types of disorder in semiconductor nanostructures. A significant source of this variability is charge disorder at the semiconductor-oxide interface, which causes unpredictable, yet, as we show here, correlated fluctuations in such essential properties of quantum dots, such as their mutual tunnel couplings, and electronic confinement energies. This study presents a systematic approach to characterize and mitigate the effects of such disorder. We use finite-element modeling of a $\mathrm{Si}$/$\mathrm{Si}$-$\mathrm{Ge}$ double quantum dot to generate a large statistical ensemble of devices, simulating the impact of trapped interface charges. This work results in a predictive statistical model capable of generating realistic artificial data for training machine-learning algorithms. By applying principal component analysis to this dataset, we identify the dominant modes through which disorder affects the multidimensional parameter space of the device. Our findings show that the parameter variations are not arbitrary, but are concentrated along a few principal axes—i.e., there are significant correlations between many properties of the devices. We finally compare that against control modes generated by sweeping the gate voltages, revealing limitations of the plunger-only control. This work provides a framework for enhancing the controllability and tunability of spin qubit devices, by systematically addressing the nature of electrostatic disorder that leads to statistical correlations in properties of double quantum dots.

Obtaining accurate representations of the eigenstates of an array of coupled superconducting qubits is a crucial step in the design of circuit quantum electrodynamics- (circuit-QED) based quantum processors. However, exact diagonalization of the device Hamiltonian is challenging for system sizes beyond tens of qubits. Here, we employ a tensor network method based on a variant of the density matrix renormalization group (DMRG) algorithm, DMRG-X, to efficiently obtain localized eigenstates of a two-dimensional transmon array without the need to first compute lower-energy states. We also introduce MTDMRG-X, a new algorithm that combines DMRG-X with multitarget DMRG to efficiently compute excited states even in regimes with strong eigenstate hybridization. We showcase the use of these methods for the analysis of long-range couplings in a multitransmon Hamiltonian including qubits and couplers, and we discuss eigenstate localization. These developments facilitate the design and parameter optimization of large-scale superconducting quantum processors.

Controlling the residual potential of test masses via the photocurrent-equilibrium mechanism is a promising method for space-based gravitational-wave detectors. This paper systematically investigates the photocurrent-equilibrium mechanism under the cooperative interaction between photon distribution and electric field. An analytical model for the residual potential is developed, and all photoelectric combinations that achieve zero residual potential are identified. Furthermore, a photoelectric decoupling method is proposed and experimentally validated using a torsion pendulum system. The results demonstrate a linear relationship ($R^2$ > 0.99) between the residual potential at equilibrium and instantaneous injection voltage for both illumination cases (test mass illumination and electrode housing illumination), enabling control within ±7 mV and meeting the requirements of space-based gravitational-wave detectors. This study elucidates the cooperative mechanism of photoelectricity and provides critical experimental validation for in-orbit applications.

We demonstrate a double-layer all-optical inference platform for classification using cascaded nonlinear diffraction. The system utilizes a dual-pass configuration through a nonlinear optical crystal, shaping a superposition of Laguerre-Gaussian modes across two layers to steer optical intensity into class-specific detector regions. By optimizing via an in situ genetic algorithm with 10 trainable degrees of freedom, we achieve 88.65% accuracy on the ten-class Modified National Institute of Standards and Technology (MNIST) dataset, leveraging crystal temperature as a critical hyperparameter to optimize noncollinear mode mixing. This work establishes a robust pathway for high-accuracy, low-complexity all-optical computing through structured light and cascaded nonlinear optical interactions.

Metamaterials derive their unconventional properties from engineered microstructures, with periodic lattices providing a versatile framework for modeling wave propagation. Dispersion relations, obtained from Bloch-Floquet theory, govern how waves propagate, attenuate, or localize within such systems. Extending interactions beyond nearest neighbors, through nonlocality, substantially enriches the design space of band diagrams, enabling phenomena such as negative or zero group velocities, rotonlike extrema, and band-gap localization. However, existing approaches to dispersion tailoring often rely on analytical formulations or Fourier-based identifications, which become impractical for complex coupling mechanisms and offer limited control over physical constraints such as stiffness positivity. This work introduces a general interpolation-based framework for customizing dispersion relations in uniform nonlocal lattices. Rather than reconstructing full dispersion curves, the method enforces prescribed frequency-wave number points as interpolation constraints, enabling localized and tunable control of wave behavior. The formulation is applied to both spring- and beam-interaction lattices, and demonstrated on an Euler-Bernoulli beam model with adjustable nonlocal couplings. Through systematic parameter tuning, the framework enables the creation of rotons, the adjustment of group-velocity dispersion, and the design of evanescent waves with controlled exponential decay within band gaps, all while ensuring real, positive-only stiffness parameters and passive mechanical behavior. Altogether, this parametric interpolation strategy provides a physically consistent and computationally efficient route for engineering advanced phononic functionalities in periodic nonlocal systems.

We present a technique based on an ensemble of nitrogen-vacancy (N-$V$) centers in diamond capable of imaging magnetic fields with high spatiotemporal resolution and sensitivity. A focused laser beam is raster scanned using an acousto-optic deflector and N-$V$ center fluorescence is read out with a single photodetector, enabling near shot-noise-limited imaging. The method operates in what we term quasi-continuous-wave optically detected magnetic resonance (qCW-ODMR), a regime closely related to pulsed-ODMR schemes used to mitigate power broadening. In this qCW regime, N-$V$ centers experience short optical pump pulses for spin polarization and readout while the microwave field continuously drives the spin transitions. We systematically characterize this regime and show that the spin response is governed by a tunable interplay between coherent evolution and relaxation, determined by the temporal spacing between pump laser pulses. Notably, the technique does not require precise microwave pulse control, thus simplifying experimental implementation. To demonstrate its capabilities, we image time-varying magnetic fields from a microwire with submillisecond temporal resolution. This approach enables flexible spatial sampling and, with our diamond, achieves $\mathrm{nT}/\sqrt{\mathrm{Hz}}$-level per-pixel sensitivity, making it a promising platform for imaging weak, dynamic magnetic fields in biological and other complex systems.

Near-field radiative heat transfer (NFRHT), primarily caused by evanescent wave tunneling in the near-field region, between a doped silicon metasurface (${\mathrm{M}}_{\mathrm{Si}}$) and a ${\mathrm{Si}\mathrm{O}}_2$ slab was investigated, employing rigorous coupled-wave analysis (RCWA) with the scattering matrix formalism. It was found that NFRHT is significantly enhanced in the frequency bands, owing to the hybrid modes coexcited by the surface plasmon polaritons of the ${\mathrm{M}}_{\mathrm{Si}}$ and the surface phonon polaritons of ${\mathrm{Si}\mathrm{O}}_2$. A transient all-optical method was proposed for NFRHT, based on focused ion beam (FIB) deposition, to measure the heat flux between patterned surfaces. It was experimentally demonstrated that, in a small near-field region, such as 100 nm, compared with RCWA, the effective medium theory (EMT) exhibits large deviations and cannot explain the physical mechanism of NFRHT well in artificial structures of a micrometer-scale period. In addition, the NFRHT mechanism was clarified by comparing the patterned ${\mathrm{M}}_{\mathrm{Si}}$ and unpatterned ${\mathrm{Si}\mathrm{O}}_2$, paving the way for the physical research and applications of NFRHT.

Thermal and photothermal effects play an increasing role at the nanoscale due to the general decrease in thermal conductances and the increasing role of interfaces. Here, we present a noncontact optomechanical analysis of the thermal and photothermal properties of suspended nanowires based on pump-probe response measurements: a probe laser measures the nanowire deformations and property changes caused by an intensity-modulated pump laser launching thermal waves propagating along the one-dimensional conductor. The spatiotemporal structure of the thermal waves propagating within the nanowire is imaged by exploiting the temperature-induced optical reflectivity changes of the nanowire. The analysis of the dominant photothermal contributions to the nanowire response in the spectral and spatial domains allows us to reach a quantitative understanding of their photothermal responses and, in particular, to quantify the interfacial contact resistance, detect internal optical Mie resonances, and image absorption inhomogeneities. Finally, we investigate how those thermal waves, through the temperature dependence of the local material stiffness, are responsible for a dynamical modulation of the nanowire vibration frequency in the resolved-sideband regime, providing novel analytical tools to further inspect the structural properties of nano-optomechanical systems with a large signal-to-noise ratio. The precise discrimination between the dominant photothermal mechanisms is enabled here by the measurement and analysis of their temporal transfer functions, in combination with the position and wavelength dependence of their photothermal response. The combination of those local and nonlocal measurements and analytical methods is generic and critical to correctly understand and mitigate the photothermal dynamical backaction processes. They allow us to refine our understanding of this often unwanted source of measurement backaction and help improve the intrinsic sensitivity of those ultrasensitive force probes.

Flying-focus techniques produce laser pulses whose focal points travel at arbitrary, controllable velocities. While this flexibility can enhance a broad range of laser-based applications, existing techniques constrain the motion of the focal point to the propagation direction of the pulse. Here, we introduce a flying-focus configuration that decouples the motion of the focus from the propagation direction. A chirped laser pulse focused and diffracted by a diffractive lens and grating creates a focal point that can move both along and transverse to the propagation direction. The focal length of the lens, grating period, and chirp can be tuned to control the direction and velocity of the focus. Simulations demonstrate this control for a holographic configuration suited to high-power pulses, in which two off-axis pump beams with different focal lengths encode the equivalent phase of a chromatic lens and grating in a gas or plasma. For low-power pulses, conventional solid-state or adaptive optics can be used instead. Multidimensional control over the focal trajectory enables new configurations for applications, including laser wakefield acceleration of ions, nonlinear Thomson scattering, and surface-plasmon emission of terahertz radiation.

The nonlinearity of magnetization precession and spin waves is a cornerstone of contemporary magnonics. We investigate nonlinear magnetization dynamics in a thin epitaxial iron film driven by femtosecond laser pulses in regimes of homogeneous precession and propagating magnetostatic spin-wave packets. The magnetization precession anharmonicity, the generation of higher-order harmonics, and the dynamical rectification are experimentally demonstrated. The numerical solution of the nonlinearized Landau-Lifshitz-Gilbert equation reveals that these effects stem from the asymmetry in the energy potential and are essentially thresholdless. This asymmetry is readily achievable when an external magnetic field with a strength comparable to the magnetic anisotropy field is applied close to the hard axis. This work establishes a connection between the geometry of the energy profile and nonlinear responses, paving the way for designing magnonic devices with controlled harmonic generation and nonlinear spin-wave interaction.