Transition-edge-sensor (TES) microcalorimeters and bolometers are used for a variety of applications. The sensors are based on the steep temperature-dependent resistance of the normal-to-superconducting transition, and are thus intrinsically sensitive to magnetic fields. Conventionally the detectors are shielded from stray magnetic fields using external magnetic shields. However, in particular for applications with strict limits on the available space and mass of an instrument, external magnetic shields might not be enough to obtain the required shielding factors or field homogeneity. Additionally, these shields are only effective for magnetic fields generated external to the TES array, and are ineffective to mitigate the impact of internally generated magnetic fields. Here we present an alternative shielding method based on a superconducting groundplane deposited directly on the backside of the silicon nitride membrane on which the TESs are located. We demonstrate that this local shielding for external magnetic fields has a shielding factor of at the least approximately $80$, and is also effective at reducing internal self-induced magnetic fields, as demonstrated by measurements and simulation of the eddy current losses in our ac-biased detectors. Measurements of 5.9-keV x-ray photons show that our shielded detectors have a high resilience to external magnetic fields, showing no degradation of the energy resolution or shifts of the energy-scale calibration for fields of several microtesla, values higher than expected in typical real-world applications.

Very recently, strongly non-Gaussian states have been observed via a direct three-mode spontaneous parametric down-conversion in a superconducting cavity [Phys. Rev. X 10, 011011 (2020)]. The created multiphoton non-Gaussian correlations are attractive and useful for various quantum information tasks. However, how to detect and classify multipartite non-Gaussian entanglement has not yet been completely understood. Here, we present an experimentally practical method to characterize continuous-variable multipartite non-Gaussian entanglement, by introducing a class of nonlinear squeezing parameters involving accessible higher-order moments of phase-space quadratures. As these parameters can depend on arbitrary operators, we consider their analytical optimization over a set of practical measurements, in order to detect different classes of multipartite non-Gaussian entanglement ranging from fully separable to fully inseparable. We demonstrate that the nonlinear squeezing parameters act as an excellent approximation to the quantum Fisher information within accessible third-order moments. The level of the nonlinear squeezing quantifies the metrological advantage provided by those entangled states. Moreover, by analyzing the above-mentioned experiment, we show that our method can be readily used to confirm fully inseparable tripartite non-Gaussian entangled states by performing a limited number of measurements without requiring full knowledge of the quantum state.

The static and dynamic properties of skyrmions have recently received increased attention due to the potential application of skyrmions as information carriers and for unconventional computing. While the current-driven dynamics has been explored deeply, both theoretically and experimentally, the theory of temperature gradient-induced dynamics—skyrmion caloritronics—is still at its early stages of development. Here, we move the topic forward by identifying the role of entropic torques due to the temperature dependence of magnetic parameters. Our results show that skyrmions move towards higher temperatures in single-layer ferromagnets with interfacial Dzyaloshinski-Moriya interactions, whereas, in multilayers, they move to lower temperatures. We analytically and numerically demonstrate that the opposite behaviors are due to different scaling relations of the material parameters as well as a non-negligible magnetostatic field gradient in multilayers. We also find a spatially dependent skyrmion Hall angle in multilayers hosting hybrid skyrmions due to variations of the thickness-dependent chirality as the skyrmion moves along the temperature gradient.

The conversion between spin and orbital angular momentum plays a crucial role in modern science and has a wide range of applications in optical multistate magnetization, optical micromanipulation, classical and quantum optical communications. However, it becomes difficult in many complex environments due to the inherent scattering effect. Here, we experimentally demonstrate the active control of spin and orbital angular-momentum conversion of light by a scattering system. We obtain significant optimization results and prove that the angular-momentum conversion process in scattering medium is tunable and flexible. Our work opens the door for high-dimensional optical information exchange in complex circumstance and paves the way for applications of optical angular momentum in optical communication.

Herein, we demonstrate the ability to optically tune the mobility of electrically powered Janus particles (JPs) that are half-coated with various zinc oxide ($\mathrm{Zn}\mathrm{O}$) semiconducting layers, i.e., polycrystalline, amorphous, and amorphous with a ${\mathrm{Si}\mathrm{O}}_2$ passivation layer. The $\mathrm{Zn}\mathrm{O}$ semiconductor photoresponse causes an increase in its electrical conductivity with light having wavelengths of sufficient photon energy with respect to the semiconductor band gap. This effect, which we name optically modulated electrokinetic propulsion (OMEP), can be harnessed to increase the contrast in polarizability between the dielectric and semiconducting hemispheres, which, in turn, results in an increased electrokinetic mobility. Optical control of electrical field propulsion enables an additional degree of control of JP mobility. We also demonstrate optical modulation of collective behavior and particle-particle interactions for dense semiconducting Janus particle populations.

Type-II superlattices (T2SLs) exemplified by $\mathrm{In}\mathrm{As}/\mathrm{Ga}\mathrm{Sb}$ are promising for infrared detection as the cutoff wavelength can simply be tuned by the layer thickness. Computational material design is thus highly desirable, but traditional methods such as tight binding and k·p depend on the choice of parameters. Ab initio density-functional-theory (DFT) calculations, on the other hand, suffer from a dilemma because band-gap accuracy and computational efficiency cannot be reached simultaneously due to band-gap underestimation. Here we show the great potential of the shell DFT-1/2 method in the material design of T2SLs. With a single parameter input, the lattice constant, or even without parameter, the method yields satisfactory electronic structures for a series of $\mathrm{In}\mathrm{As}/\mathrm{Ga}\mathrm{Sb}$ T2SLs considering spin-orbit coupling, with the band-gap mismatch limited to 5% compared with our industry-class samples. Detailed miniband analysis is presented based on the ab initio results. For covalent semiconductors without strong correlation, shell DFT-1/2 proves to be an excellent candidate for accurate band-structure calculation with local-density-approximation-level efficiency. It enables the material design of III-V superlattice materials at the engineering level without introducing empirical parameters.

Continuous-variable (CV) entanglement constitutes a powerful approach to deterministic quantum information protocols. Improving the scale of entanglement is of vital importance for enhancing the information capacity of quantum information protocols. Here we demonstrate the deterministic generation of CV entanglement of large-scale Hermite-Gaussian (HG) modes from the four-wave mixing (FWM) process in an atomic vapor. In our experiment, 56 pairs of entangled HG modes are deterministically and simultaneously generated from the FWM process, which increases the number of entangled spatial mode pairs in the CV system. Meanwhile, we experimentally verify the existence of CV entanglement between the evolution process from HG mode to Laguerre-Gaussian mode. Our results shed light on constructing high-capacity CV quantum information protocols and provide a promising platform to study CV entanglement.

We present a method for quantum tomography of multiqubit states. We apply the method to spin-multiphoton states, which we generate using a quantum dot based device. Periodic excitation of a quantum dot confined spin deterministically generates strings of entangled photons in a cluster state, threefold faster than previously demonstrated. Our tomography method uses time-resolved polarization-sensitive multiphoton correlation measurements to measure both the polarization of the confined spin and that of the emitted photons. We develop an edge-sensitive gradient-descent algorithm and apply it to the acquired data to map the periodic physical process that generates the cluster state. We utilize our tomographic method to optimize our quantum dot based device and show that the enhanced generation rate increases the entanglement robustness of the generated multiqubit state.

Optomechanical systems show great potential as quantum transducers and information storage devices for use in future hybrid quantum networks. In this context, optomechanical strong coupling can enable efficient, high-bandwidth, and deterministic transfer of quantum states. While optomechanical strong coupling has been realized at optical frequencies, it has proven difficult to identify a robust optomechanical system that features the low loss and high coupling rates required for more sophisticated control of mechanical motion. In this paper, we demonstrate strong coupling in a Brillouin-based bulk cavity optomechanical system in both the single-mode and the multimode strong-coupling regime, which leads to a useful device both for applications in quantum information and for investigating decoherence phenomena in bulk acoustic wave resonators. Using nontrivial mode hybridizations in the strong-coupling regime, we create hybridized photonic-phononic modes with lifetimes that are significantly longer than those of the uncoupled system. This surprising lifetime enhancement, which results from the interference of decay channels, showcases the use of multimode strong coupling as a general strategy to control extrinsic decoherence mechanisms. Moreover, phonons supported by such bulk-acoustic-wave resonators have a collection of properties, including high frequencies, long coherence times, and robustness against thermal decoherence, that make this optomechanical system particularly enticing for applications such as quantum transduction and memories. Hence, this system provides access to phenomena in a previously unexplored regime of optomechanical interactions and could serve as an important building block for future quantum devices.

One of the main bottlenecks in the pursuit of a large-scale–chip-based quantum computer is the large number of control signals needed to operate qubit systems. As system sizes scale up, the number of terminals required to connect to off-chip control electronics quickly becomes unmanageable. Here, we discuss a quantum-dot spin-qubit architecture that integrates on-chip control electronics, allowing for a significant reduction in the number of signal connections at the chip boundary. By arranging the qubits in a two-dimensional array with about $12\mu \mathrm{m}$ pitch, we create space to implement locally integrated sample-and-hold circuits. This allows us to offset the inhomogeneities in the potential landscape across the array and to globally share the majority of the control signals for qubit operations. We make use of advanced circuit modeling software to go beyond conceptual drawings of the component layout, to assess the feasibility of the scheme through a concrete floor plan, including estimates of footprints for quantum and classical electronics, as well as routing of signal lines across the chip using different interconnect layers. We make use of local demultiplexing circuits to achieve an efficient signal-connection scaling, leading to a Rent’s exponent as low as $p=0.43$. Furthermore, we use available data from state-of-the-art spin qubit and microelectronics technology development, as well as circuit models and simulations, to estimate the operation frequencies and power consumption of a million-qubit array. This work presents a complementary approach to previously proposed architectures, focusing on a feasible scheme to integrating quantum and classical hardware, and identifying remaining challenges for achieving full fault-tolerant quantum computation. It thereby significantly closes the gap towards a fully CMOS-compatible quantum computer implementation.

We report an infrared (IR) imaging study of trilayer graphene (TLG) with both ABA (Bernal) and ABC (rhombohedral) stacking orders using the scattering-type scanning near-field optical microscope (SSNOM). With the SSNOM operating in the mid-IR region, we map in real space the surface plasmon polaritons of ABA TLG and ABC TLG, which are tunable with electrical gating. Through quantitative modeling of plasmonic imaging data, we find that the plasmon wavelength of ABA TLG is significantly larger than that of ABC TLG, resulting in a sizable impedance mismatch and hence a strong plasmon reflection at the ABA/ABC lateral junction. Further analysis indicates that the different plasmonic responses of the two types of TLG are directly linked to their distinct electronic structures and carrier properties. Our work uncovers the physics behind the stacking-dependent plasmonic responses of TLG and sheds light on future applications of TLG and the ABA/ABC junctions in IR plasmonics and planar nano-optics.

Active materials with distinctive nonequilibrium properties have diverse materials science applications. Active systems are common in living matter, such as the filament network in the cell that is activated by molecular motors, and in materials science as exemplified by hydrogels activated by chemical reactions. Here we describe another class of active polymeric filament systems where the filaments are activated by embedded chemically powered nanomotors that have catalytic and noncatalytic parts. Chemical reactions on the catalytic surfaces produce forces that act on the polymeric filaments. By changing the nonequilibrium conditions, these forces can be made to change sign and thereby compress or expand the filaments. The embedded motors provide both the source of activity and the means to control the filament conformational structure. As an example of control, we show that oscillatory variations of the chemical constraints yield gel-like networks that oscillate between expanded or compressed forms, much like those of hydrogels.

The material family of $Y$-type hexaferrites is among the most promising candidates for magnetoelectric memory applications. The magnetoelectric properties in this class of magnets are dominated by a multiferroic phase, termed the FE3 phase, where spin-driven polarization can be switched by a magnetic field, and, conversely, a full magnetic moment can be reversed by an electric field. In this study, we discuss the effect of Cr doping on the stability of competing magnetic and multiferroic phases in the $Y$-type hexaferrites ${\mathrm{Ba}\mathrm{Sr}\mathrm{Co}}_2{\mathrm{Fe}}_{12-x-\delta }{\mathrm{Al}}_x{\mathrm{Cr}}_{\delta }{\mathrm{O}}_{22}$ with $x=0.9$ and $\delta =0.00$, 0.05, and 0.10. We find that Cr doping increases the stability of the multiferroic FE3 phase; while in the Cr-free compound the alternating longitudinal conical (ALC) and proper screw phases are stabilized as zero-field-cooled magnetic phases, the FE3 phase appears besides the ALC phase as a stable zero-field-cooled phase in the $\delta =0.05$ and 0.10 compounds. Moreover, a spin-induced large polarization is observed at and above room temperatures with antisymmetric magnetic field dependence. The magnetoelectric properties, in particular the coupling between polarization and magnetization, are investigated via the measurements in the simultaneous presence of electric and magnetic fields. We find the enhanced stability of the magnetoelectic responses from the multiferroic FE3 phase upon Cr doping, while the coupling between the polarization and magnetization is preserved.

Acoustic waves are ubiquitous in everyday human experience, therefore, precise control over the deformation of acoustic waves is always extremely desirable, which can be used, for example, to transform or hide objects from incident waves. Acoustic illusion devices are generally implemented by transformation acoustics, which can deceive ears or sonar systems. Challenges remain, for example, the complex and extreme material parameters prescribed by coordinate transformation theory make the implementations particularly difficult, even with the help of acoustic metamaterials. Here, the method based on Fabry-Perot resonances offers a feasible solution for achieving three-dimensional (3D) omnidirectional passive acoustic illusion. We theoretically demonstrate 3D acoustic illusion via Mie theory, a reduced version is further designed numerically and implemented experimentally. Our work opens possibilities for the implementation of modern acoustic illusion devices in the future, such as camouflage for antisonar detection.