Negatively charged silicon vacancy ($\mathrm{Si}$${\mathrm{V}}^{-}$) centers in diamond are leading candidates for solid-state quantum memory that can be controlled using electromagnetic or acoustic waves. The latter are particularly promising due to the strong strain response of $\mathrm{Si}$${\mathrm{V}}^{-}$, enabling large spin-phonon interaction strengths. Indeed, coherent spin control via surface acoustic waves (SAWs) has been demonstrated and is essential for developing on-chip phononic quantum networks. However, the absence of piezoelectricity in diamond requires an interface with a piezoelectric material for efficient transduction and delivery of acoustic waves to spins in diamonds. Here, we demonstrate a heterogeneously integrated phononic platform that combines thin-film lithium niobate with diamond to enable acoustic control of single $\mathrm{Si}$${\mathrm{V}}^{-}$ spins. Additionally, leveraging large SAW-induced strain at the location of $\mathrm{Si}$${\mathrm{V}}^{-}$, we achieve coherent acoustic control of an electron spin with more than twofold improvement in Rabi frequency compared to state-of-the-art devices based on aluminum nitride on diamond. This work represents a crucial step towards realizing phonon-based quantum information processing systems.

Linear optical networks are fundamental to the advancement of quantum technologies, including quantum computing, communication, and sensing. The accurate characterization of these networks, described by unitary matrices, is crucial to their effective utilization and scalability. In this work, we present a method for reconstructing the transfer matrix of a linear optical interferometer based on the analysis of cross-correlation functions of photon counts between pairs of output modes. Our approach accounts for losses and photon indistinguishability, making it robust to experimental imperfections. By minimizing the requirements for the input states, the method simplifies the experimental implementation. We demonstrate the effectiveness of our technique through theoretical modeling and experimental validation in a four-mode programmable integrated optical interferometer. The results show high fidelity in matrix reconstruction and successful application in boson sampling experiments. In addition, we provide a comprehensive formalism for correlation functions and discuss the robustness of the method to measurement errors. This work offers a practical and efficient solution for characterizing linear optical networks, paving the way for scaling up photonic quantum technologies.

The rotational Doppler effect (RDE), pivotal in metrology and communication, has been exclusively observed through angular momentum transfer from incoming waves to rotating objects, limiting its compactness and practicality. Here we demonstrate an RDE phenomenon originating directly from rotating objects without incoming waves. We show that the steady loading on a rotor inherently generates spinning acoustic vortex (AV) modes, which share the object’s angular velocity and carry orbital angular momentum. These spinning AV modes produce different rotational Doppler shifts, and the resulting acoustic energy is correlated with AV phase stability. Furthermore, we reveal that rotor tonal noise arises from the constructive interference of AV modes with identical topological charges generated by each blade. Our work builds a bridge between rotor tonal noise in aeroacoustics and AVs carrying orbital angular momentum in classical acoustics via the disclosed RDE from rotating objects. On one hand, we leverage steady blade loading to compactly generate tunable AV modes. On the other hand, we exploit AV characteristics to achieve highly robust noncontact detection of rotating objects and further reveal the phase synchronization mechanism for tonal noise reduction. Our findings have the potential to stimulate further research and may pave the way for new applications based on the RDE.

Superconducting qubits are often adversely affected by two-level systems (TLSs) within the Josephson junction, which contribute to decoherence and subsequently limit the performance of the qubit. By treating the TLS as a soft (i.e., low-frequency) bosonic mode localized in real space, we find that a single TLS in either the amorphous-oxide surface or the superconducting bulk may result in a localized “hot spot” of amplified Josephson energy. Such amplification is shown to have a non-negligible effect on the $T_1$ time of a simple phase qubit, regardless of whether or not the TLS is on resonance with the qubit frequency. With this study, we identify unique fingerprints of TLS defects in the Josephson current and qubit decoherence time.

Tailoring quantum-error-correction codes (QECCs) to biased noise has demonstrated significant benefits. However, most of the prior research on this topic has focused on code-capacity noise models. Furthermore, a no-go theorem prevents the construction of controlled-not (cnot) gates for two-level qubits in a bias-preserving manner which may, in principle, imply that noise bias cannot be leveraged in such systems. In this work, we show that a residual bias up to $\eta \sim 5$ can be maintained in cnot gates under certain conditions. Moreover, we employ controlled-Z (cz) gates in syndrome-extraction circuits and show how to natively implement these in a bias-preserving manner for a broad class of qubit platforms. This motivates the introduction of what we call a hybrid biased-depolarizing (HBD) circuit-level noise model that captures these features. We numerically study the performance of the $XZZX$ surface code and observe that bias-preserving cz gates are critical for leveraging biased noise. Accounting for the residual bias present in the cnot gates, we observe an increase in the code threshold up to a $1.27\mathrm{\%}$ physical error rate, representing a $90\mathrm{\%}$ improvement. Additionally, we find that the required qubit footprint can be reduced by up to $75\mathrm{\%}$ at relevant physical error rates.

Terahertz (THz) sources emitting single-period pulses have been extensively studied and applied. However, multi-period THz sources remain scarce. In this work, we utilize a THz emission spectroscopy (TES) system to investigate the THz emission characteristics of quartz single crystals. It is demonstrated that the THz waves emitted from the quartz are generated via the optical rectification (OR) effect, and their radiation intensity is influenced by the thickness and azimuth angle of the quartz. Notably, multi-cycle THz waves can be successfully achieved by stacking several slices of quartz with a specific azimuth angle. The THz peak signal from two stacked layers is nearly twice that of a single-layer sample. Moreover, the number of cycles can be modulated by adjusting the number of stacked quartz layers. In addition, it is shown that linearly polarized THz waves can still be generated under the excitation of both left- and right-handed circularly polarized light. However, these waves exhibit opposite polarities and different signal amplitudes. Our work proposes a new method to generate single or multi-cycle THz waves using cost-effective quartz materials, which may open up new possibilities in the field of THz technology.

Physical matching has long been a cornerstone of secure authentication systems, as exemplified by the Tiger Amulet in ancient military contexts. However, traditional methods are constrained by reliance on tangible objects and the necessity of “localized” matching within physical space. Ghost imaging (GI), which utilizes correlated light beams for indirect object reconstruction, presents a promising alternative for nonlocalized verification. Despite significant progress, second-order correlation-based GI techniques are limited to assessing object similarity and cannot capture the complementary relationship between objects that together form a complete entity. In this study, we introduce a third-order thermal GI approach for complementary object matching. By employing three correlated beams, this technique enables the secure authentication of objects that form a unified whole. When complementary objects match the reference object, a distinct correlation peak is observed, whereas a mismatch results in noise. This optical authentication mechanism holds considerable potential for enhancing security in communication and encryption systems.

Efficient manipulation of the antiferromagnetic (AFM) state is desirable for advanced spintronic devices with fast operation and robustness regarding magnetic field perturbation. In this article, we demonstrate deterministic bipolar AFM spin reversal induced by a low voltage below 0.8 V (51 mV/nm) based on the magnetoelectric (ME) effect in a $\mathrm{Pt}$/${\mathrm{Cr}}_2{\mathrm{O}}_3$/$\mathrm{Ir}$ epitaxial trilayer. A stable spin direction is determined depending on the sign of the electric field and magnetic field product, enabling deterministic access to four quadrants in E-H space. With the help of first-principles calculations, we show that the voltage effect on the magnetic anisotropy energy density is a minor effect, whereas the ME effect determines both the stable spin state and the switching behavior. Our findings not only advance voltage-based insulating AFM spintronics but also provide a basis for the device function, such as a deterministic logic operation by means of the field combination.

The transmon, a fabrication-friendly superconducting qubit, remains a leading candidate for scalable quantum computing. Recent advances in tunable couplers have accelerated progress toward high-performance quantum processors. However, extending coherent interactions beyond millimeter scales to enhance quantum connectivity presents a critical challenge. Here we introduce a hybrid-mode coupler exploiting resonator-transmon hybridization to simultaneously engineer the two lowest-frequency modes, enabling high-contrast coupling between transmons spaced at a centimeter-scale distance. For a 1-cm coupler, we experimentally demonstrate flux-tunable hybrid modes and measure strong $XX$ and $ZZ$ couplings between qubits exceeding 23 and 10 MHz, respectively, under current conditions, in agreement with an effective two-channel model. Our theoretical model further suggests $ZZ$ coupling strengths reaching 100 MHz, with modulation contrasts exceeding ${10}^4$. This work provides an efficient pathway to mitigate the inherent connectivity constraints imposed by short-range interactions, enabling transmon-based architectures compatible with hardware-efficient quantum tasks.

Differential operation is an integral component of wave-based computation and has been extensively employed in signal processing applications. Nevertheless, current acoustic differentiators are essentially restricted to functioning independently in the temporal or spatial domains. Here, we propose an acoustic spatiotemporal differentiator (ASTD) utilizing an acoustic metagrating (AMG) that simultaneously performs first-order differentiation and generates a spatiotemporal vortex (STV). By breaking spatial mirror symmetry, the ASTD possesses a transfer function exhibiting linear dependence on both spatial wave-vector and temporal frequency, thereby enabling the first-order differentiation. A theoretical analysis reveals that, when introducing a π/2 phase delay between spatial and temporal differentiations, the ASTD can produce an STV with a topological charge (TC) opposite to that of the vortex in the momentum-frequency domain. Both simulations and experiments confirm the differentiation capability and STV generation of the ASTD. It is further demonstrated that the differentiator can detect sharp changes in spatiotemporal pulses even with intricate profiles. These findings offer a promising platform for advancing acoustic computing and signal processing in the spatiotemporal domain.

Quantum random-number generators (QRNGs), based on the principles of quantum mechanics, are capable of producing truly unpredictable random numbers and have wide applications in many fields. As a key index, QRNGs with high generation speed across various scenarios are becoming increasingly needed. However, in conventional time-domain processing, the generation rate of high-speed QRNGs is limited by the bandwidth and sampling rate of electrical devices. In this work, we propose a quantum random-number generation scheme based on frequency-domain processing. By partitioning the power spectrum of phase noise into four nonoverlapping frequency bands for independent extraction and processing, we realize parallel multichannel output of random numbers. Finally, we experimentally validate our scheme and generate random numbers with rates of 44 and 52 Gbit/s in digital and analog processing, respectively. More importantly, for the generation rate of 52 Gbit/s, only devices with a bandwidth of 1 GHz and a sampling rate of $2\times {10}^9$ samples per second are used, which increases the random-bit generation rate 26 times. Thus, our method could significantly increase the generation rate with low bandwidth and low sampling rate.

Controlling the directional emission of quantum dots (QDs) is essential for applications in lighting, optical communications, biomedicine, and quantum information technologies. However, most existing strategies fail to simultaneously achieve high directionality and strong emission efficiency. Here, we present a dual-layer concentric-ring metalens optimized through inverse design powered by a deep reinforcement learning algorithm. This approach not only boosts fluorescence and directional emission but also significantly reduces the computational overhead. The proposed structure enables nonreciprocal emission control of embedded QDs, driven by unique near-field coupling and constructive interference of Bloch surface waves. A fluorescence enhancement factor of up to 5371 is achieved, with an emission divergence angle below 5°. Moreover, both the emission wavelength and directionality are tunable by varying the thickness ratio of dual-layer concentric-ring or the QD position. These findings offer promising opportunities for integrated quantum light sources and advanced biomedical photonic systems.

The rapid progress in antiferromagnetic and altermagnetic spintronics has led to increased interest in magnetic materials with vanishing net magnetization but strong spin-dependent transport properties. As thin films of such materials become central to device concepts, precise magnetic characterization is essential, to quantify intrinsic moments and interpret transport signatures such as the anomalous Hall effect. In this work, we show that commercial $\mathrm{Mg}\mathrm{O}$ substrates, commonly used in epitaxial growth, often produce substantial parasitic magnetic signals that can match or exceed the response of weakly magnetic films. We identify two major components: a low-field ferromagnetic-like contribution originating from the epi-ready surface, and a temperature-dependent paramagnetic background associated with dilute bulk impurities. These artifacts vary between samples and cannot be corrected using standard linear background subtraction or a measured reference substrate. To address this, we develop and put forward a compensation scheme that combines two complementary, nondestructive measurement protocols. We demonstrate up to 97% efficacy without requiring prior measurements of the bare substrate. The proposed framework enables reliable extraction of intrinsic magnetic signals and provides a general strategy for high-fidelity magnetometry in weakly magnetic thin-film systems, including emerging classes of materials such as topological phases and two-dimensional magnets. We also report the diamagnetic susceptibility of crystalline $\mathrm{Mg}\mathrm{O}$, ${\chi }_{\mathrm{Mg}\mathrm{O}}=-4.0\times {10}^{-7}$ emu/g/Oe.

Quantum transduction is essential for connecting quantum technologies across varied frequencies. Achieving a positive quantum capacity of a traditional quantum transduction channel is a long-pursued goal in the field. However, to overcome the high threshold remains a major challenge, owing to practical limitations. Recently, an entanglement-assisted transducer was proposed based on a cavity-optic system [Opt. Quantum 2, 475 (2024)], where a modified bosonic loss channel was obtained, and the transduction efficiency could be enhanced by properly tuning the squeezing parameters. In this paper, we further identify three types of quantum channel enabled by this design, offering additional options for implementing the proposed transduction schemes. Compared with transducers without entanglement assistance, the scheme also shows a great enhancement in the conversion bandwidth for achieving high quantum capacity, further increasing its value in practical applications.

Hong-Ou-Mandel (HOM) interference is an intrinsic quantum phenomenon that goes beyond the possibilities of classical physics, and enables various applications in quantum metrology. While the timing resolution of HOM-based sensors is generally investigated, the ultimate quantum sensitivity in the estimation of transverse deflection or displacement between paired photons interfering at a balanced beam splitter has been explored relatively little. Here we present an experimental demonstration of a spatial HOM interferometry for measuring the transverse deflection of an optical beam by using transverse momentum sampling measurements. This feasible scheme suffices to achieve great precision with comparatively little technological effort, which circumvents the stringent requirement in direct imaging resolution at the diffraction limit. We can adaptively determine optimum working points using a Fisher information analysis, and demonstrate an optimized spatial HOM interferometry according to practical applications. These results may significantly facilitate the use of quantum interference for high-precision spatial sensing, and may pave the way to more complex quantum imaging techniques such as nanoscopic microscopy.