Achieving high-fidelity qubit readout and reset while maintaining qubit coherence is crucial for quantum error correction and advanced quantum algorithms. Here, we design and experimentally demonstrate a scalable architecture based on frequency-tunable nonlinear Purcell filters, which enables flexible readout and rapid unconditional reset of multiple superconducting qubits. Our readout protocol dynamically adjusts the effective linewidth of the readout resonator through a tunable Purcell filter, optimizing the signal-to-noise ratio during measurement while suppressing photon noise during idle periods. Combined with a multilevel readout protocol, we achieve the highest readout fidelity of 99.3% without any quantum-limited amplifier, even with a small dispersive shift. Moreover, by leveraging a reset channel formed via the adjacent coupling between the filter and the coupler, we realize unconditional qubit reset of both leakage-induced |2⟩ and |1⟩ states within 200 ns and reset of the |1⟩ state alone within 75 ns, with error rates ≤1%. The filter also mitigates both photon-induced dephasing and the Purcell effect, thereby preserving qubit coherence. This scalable Purcell filter architecture shows exceptional performance in qubit readout, reset, and protection, marking it as a promising hardware component for advancing fault-tolerant quantum computing systems.

Two-dimensional (2D) van der Waals heterostructures based on d-electron materials offer a platform for realizing heavy-Fermion systems with Kondo lattices. However, the nondestructive and reversible manipulation of spins at the nanoscale in 2D heavy-Fermion materials─essential for their application in spintronic devices─remains elusive. In this paper, we successfully manipulate and characterize both spin (Kondo effects) and electronic (charge density wave) degrees of freedom in the 2D heavy-Fermion system of 1T/1H-TaSe2 heterostructure using scanning tunneling microscopy/spectroscopy (STM/STS). By applying voltage pulses, we precisely control the chirality and arrangement of the charge density wave coupled with local spins in 1T-TaSe2. This process also leads to the generation and annihilation of two distinct types of domain walls (DWs). Combining STS and first-principles calculations, we reveal that the local spins are quenched in the type-II DW, which forms between two domains exhibiting a phase shift yet possessing identical chirality. This results in the disappearance of the Kondo resonance. The Mott phase also quenches within type-II DWs. Our results demonstrate a nondestructive and reversible approach to manipulate and understand the local spins of the Kondo lattice in artificial 2D heavy-Fermion systems with nanoscale precision.

Nonlinear optical (NLO) behaviour in media can be widely used in laser components, data storage devices and etc. NLO molecular switch can alternate between two or more chemical forms displaying contrasts in its NLO response(s). For the alkali metal-adsorbed graphyne (GY) and graphdiyne (GDY), a DFT study shows that the formed M@GY and M@GDY (M=Li and Na) are, respectively, high-performance candidates for single-pole triple-throw (SP3T) and triple-pole triple-throw (3P3T) NLO molecular switches with high stability. From off form(s) to on forms in each case, the increases in second-order NLO responses, including hyper-Rayleigh scattering (beta(HRS)), electric field induced second harmonic generation (beta(//(E))), and static first hyperpolarizability (beta(0)) values, constitute 1 similar to 3 orders of magnitude improvements. Especially, the beta(HRS) and beta(//(E)) values of Na@GDY(eta(6)-1) with laser pulse wavelength of 1460 nm are up to 3.61 x 10(7) and 7.35 x 10(7) au, respectively. The near- and mid-far-infrared (NMF-IR) long transparent regions for both M@GY and M@GDY suggested they can be regarded as NMF-IR switches. The adsorption of alkali metal atoms on GY/GDY monolayers with different number and positions may generate excellent multi-responsive NLO molecular switching effects.

Matter at the atomic-scale is inherently governed by the laws of quantum mechanics. This makes charges and spins confined to individual atoms—and interactions among them—an invaluable resource for fundamental research and quantum technologies alike. However, harnessing the inherent ‘quantumness’ of atomic-scale objects requires that they can be precisely engineered and addressed at the individual atomic level. Since its invention in the 1980s, scanning tunnelling microscopy (STM) has repeatedly demonstrated the unrivalled ability to not only resolve but manipulate matter at atomic length scales. Over the past decades, this has enabled the design and investigation of bottom-up tailored nanostructures as reliable and reproducible platforms to study designer quantum physics and chemistry, band topology, and collective phenomena. The vast range of STM-based techniques and modes of operation, as well as their combination with electromagnetic fields from the infrared to microwave spectral range, has even allowed for the precise control of individual charge and spin degrees of freedom. This roadmap reviews the most recent developments in the field of atomically-engineered quantum platforms and explores their potential in future fundamental research and quantum technologies.

Two-dimensional heterojunctions provide a versatile platform for exploring various quantum properties. Here, we create bilayer 1T/2H-NbSe2 heterophase junctions and realize two types of stacking configurations with picometer-level lattice shifts. By high-resolution scanning tunneling microscopy/spectroscopy, we found that the electronic states are highly dependent on the stacking configurations of the 1T layer on the 2H one. Unexpectedly, a tiny shift between the two configurations (about 110 pm in the lateral direction and 30 pm in the vertical one) leads to a change from a correlated gap lattice into a Kondo peak lattice. Moreover, both of them show a spin-related pseudogap width of 2-3 meV close to the Fermi level, which splits under the external magnetic field. Our study demonstrates the important role of delicate stacking configurations on the many-body physics and spin-related phenomena in the heterophase junctions.

Controlling quantum interference near avoided energy-level crossings is crucial for fast and reliable coherent manipulation in quantum information processing. However, achieving tunable quantum interference in atomically-precise engineered structures remains challenging. Here, we demonstrate electrical control of quantum interference using atomic spins on an insulating film in a scanning tunneling microscope. Using bias voltages applied across the tunnel junction, we modulate the atomically-confined magnetic interaction between the probe tip and surface atoms with a strong electric field, and drive the spin state rapidly through the energy-level anticrossing. This all-electrical manipulation allows us to achieve Landau-Zener-Stückelberg-Majorana (LZSM) interferometry on both single spins and pairs of interacting spins. The LZSM pattern exhibits multiphoton resonances, and its asymmetry suggests that the spin dynamics is influenced by spin-transfer torque of tunneling electrons. Multi-level LZSM spectra measured on coupled spins with tunable interactions show distinct interference patterns depending on their many-body energy landscapes. These results open new avenues for all-electrical quantum manipulation in spin-based quantum processors in the strongly driven regime.

This letter presents a pioneering magnetoelectric dipole (MED) resonator designed to enhance the directional sensitivity. Unlike traditional omnidirectional Rydberg atomic sensors (RASs) that struggle to selectively amplify signals from specific directions, this innovative resonator is directional and foregoes the need for a feed port, which is common in antenna designs. Instead, it boosts RAS sensitivity by intensifying local electric fields, thereby imparting the sensor with the directional properties of the MED and significantly reducing backlobe levels. Guided by the theory of characteristic mode, the resonator features an open cavity with a rectangular ring and two horizontal metal plates, creating magnetic and electric dipole resonator structures. It integrates a local oscillator port to support atomic heterodyne techniques, further improving sensitivity. The design impressively attains a peak electric field gain of 22 dB within a compact size while maintaining stable and directional patterns. These attributes render the resonator ideal for directional detection in RAS applications.

Artificial quantum systems have emerged as platforms to realize topological matter in a well-controlled manner. So far, experiments have mostly explored non-interacting topological states, and the realization of many-body topological phases in solid-state platforms with atomic resolution has remained challenging. Here we construct topological quantum Heisenberg spin lattices by assembling spin chains and two-dimensional spin arrays from spin-1/2 Ti atoms on an insulating MgO film in a scanning tunnelling microscope. We engineer both topological and trivial phases of the quantum spin model and thereby realize first- and second-order topological quantum magnets. We probe the many-body excitations of the quantum magnets by single-atom electron spin resonance with an energy resolution better than 100 neV. Making use of the atomically localized magnetic field of the scanning tunnelling microscope tip, we visualize various many-body topological bound modes including topological edge states, topological defects and higher-order corner modes. Our results provide a bottom-up approach for the simulation of exotic quantum many-body phases of interacting spins. Atom manipulation in a scanning tunnelling microscope allows the fabrication of artificial topological quantum magnets. Single-atom electron spin resonance experiments probe the many-body topological modes of the quantum magnets and provide a visualization.

Controlling spin-polarized currents at the nanoscale is of immense importance for high-density magnetic data storage and spin-based logic devices. As electronic devices are miniaturized to the ultimate limit of individual atoms and molecules, electronic transport is strongly influenced by the properties of the individual spin centers and their magnetic interactions. In this work, we demonstrate the precise control and detection of spin-polarized currents through two coupled spin centers at a tunnel junction by controlling their spin-spin interactions. We attach a nickelocene (Nc) molecule to a scanning probe tip and place it over a spin center (either an Fe atom or another Nc molecule) located on a surface. By changing the adsorption orientation of Nc at the tip apex and adjusting the tip-sample distances, we control the wave function overlap between two spin systems, resulting in strong changes in their magnetic exchange coupling, quantum spin states, and spin excitation energies. Coupling the Nc molecule to the surface spin induces exchange-split spin states, enabling the quantitative determination of the spin polarization of tunnel currents. Strongly asymmetric tunneling spectra reveal almost 100% spin-polarized currents through the coupled Nc-Fe spin system. Our findings highlight the potential of these spin systems at the tunnel junction for high-performance spin-based devices engineered at the atomic scale.

Quantum coherent physics and chemistry concern the creation and manipulation of an excited-state manifold that contains the superposition and entanglement of multiple quantum levels. Electromagnetic waves such as light and microwave can be used to generate and probe different quantum coherent phenomena. The recent advances in scanning tunneling microscopy (STM) techniques including ultrafast laser coupled STM and electron spin resonance STM combine electromagnetic excitation with tunneling electron detection, bringing the investigation of quantum coherence down to the atomic and molecular level. Here, we survey the latest STM studies of different quantum coherent phenomena covering molecular vibration, electron transfer, surface plasmon resonance, phonon, spin oscillation, and electronic transition, and discuss the state and promise of characterizing and manipulating quantum coherence at the atomic or molecular scale.

Coherent control of individual atomic and molecular spins on surfaces has recently been demonstrated by using electron spin resonance (ESR) in a scanning tunneling microscope (STM). Here, a combined experimental and modeling study of the ESR of a single hydrogenated Ti atom that is exchange-coupled to a Fe adatom positioned 0.6-0.8 nm away by means of atom manipulation is presented. Continuous wave and pulsed ESR of the Ti spin show a Rabi rate with two contributions, one from the tip and the other from the Fe, whose spin interactions with Ti are modulated by the radio-frequency electric field. The Fe contribution is comparable to the tip, as revealed by its dominance when the tip is retracted, and tunable using a vector magnetic field. The new ESR scheme allows on-surface individual spins to be addressed and coherently controlled without the need for magnetic interaction with a tip. This study establishes a feasible implementation of spin-based multi-qubit systems on surfaces.

Here we report a low-temperature and vector-magnetic-field scanning tunneling microscopy/spectroscopy (STM/S) study on 3R-TaSe2. The sample surface was obtained by exfoliating a bulk 3R-TaSe2 single crystal in an ultrahigh-vacuum (UHV) chamber and then transferred in situ to STM. It was observed that the topmost layer shows a 3 × 3 charge density wave pattern at T = 4.2 K with metallic character in STS. The electronic characterization study by variable-temperature and magnetic field STS revealed that 3R-TaSe2 behaves as a type-II superconductor. More intriguingly, such superconductivity (SC) can survive under strong in-plane magnetic fields even up to 2.5 T and out-of-plane magnetic fields up to 0.7 T, exhibiting an anisotropic superconducting property. Temperature-dependent STS showed that 3R-TaSe2 undergoes a transition above 0.58 K. Our results may be important for understanding the intriguing SC properties of the 3R-phase van der Waals materials.

: Scanning tunneling microscopes (STM) equipped with pulsed electron spin resonance (ESR) have paved a way to coherently control individual atomic and molecular spins on surfaces. A recent breakthrough was to drive ESR of a spin outside the tunnel junction by locating a single atom magnet in proximity to a qubit, composing a 'spin-magnet pair'. Here we present a combined experimental and model study on the ESR driving mechanism in such a spin-magnet pair. Pulsed ESR of a single hydrogenated Ti atom on MgO with an Fe atom located between 6 and 8 Å away showed a non-vanishing Rabi rate even when the tip is substantially retracted, comparable in strength with that driven by the interaction with the tip ’s magnetic

Designing and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states. These results open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations.

Recently,the ability to drive electron spin resonance (ESR) of individual atoms using a scanning tunneling microscope (STM) provided a major step forward in sensing and manipulating magnetism at the atomic scale.The atomic-scale spatial resolution and the ultrahigh energy resolution of ESR-STM has allowed the measure-ment of the magnetic dipolar interaction between two atoms placed a few nanometers apart on a surface,the detec-tion of hyperfine interaction between electronic and nuclear spins of individual atoms,as well as the exploration of quantum fluctuations in designed spin arrays having tailored geometries.By implementing pulsed ESR,coherent spin manipulation of magnetic atoms and engineered atomic dimers on surfaces have been achieved by demonstrat-ing Rabi oscillations,Ramsey fringes and spin echoes,opening the door to a powerful suite of pulsed techniques that can extend single-atom sensing capabilities.Coherent control of spins arranged with atomic precision provides a solid-state platform for quantum simulation of many-body systems.

By doping two potassium atoms among three C20F20 cages, peanut-shaped single molecular solvated dielectron C20F20@K@C20F20@K@C20F20 as new type of spin molecular switches was theoretically presented. The triplet structure with two single-excess-electrons individually inside left and middle cages is thermodynamically more stable than the singlet one with lone pair of excess electrons inside middle cage. It is found that applying an oriented external electric field (OEEF) of 111 × 10-4 au (0.5705 V/Å) or -120 × 10-4 au (-0.6168 V/Å) in the x-axis direction firstly and then releasing it, the field-free triplet C20F20@K@C20F20@K@C20F20 with two single-excess-electrons can change into singlet one with lone pair of excess electrons through a singlet one with lone pair of excess electrons inside the end cage. Different spin states can bring significantly different dipole moment component values and considerable different intensities of maxumum wavelengths in intense absorption band. Therefore, C20F20@K@C20F20@K@C20F20 is a good candidate for spin molecular switching materials.

Magnetic resonance imaging (MRI) revolutionized diagnostic medicine and biomedical research by allowing non-invasive access to spin ensembles1. To enhance MRI resolution to the nanometre scale, new approaches2–4 including scanning probe methods5–8 have been used in recent years, which culminated in the detection of individual spins5,6. This allowed for the visualization of organic samples9 and magnetic structures10,11, as well as identifying the location of electron7,8 and nuclear spins12. Here, we demonstrate the MRI of individual atoms on a surface. The set-up, implemented in a cryogenic scanning tunnelling microscope, uses single-atom electron spin resonance13,14 to achieve subångström resolution, exceeding the spatial resolution of previous MRI experiments5–8 by one to two orders of magnitude. We find that MRI scans of different atomic species and with different probe tips lead to unique signatures in the resonance images. These signatures reveal the magnetic interactions between the tip and the atom, in particular magnetic dipolar and exchange interaction. The authors demonstrate that individual atoms on a surface can be detected and distinguished from each other with subångström resolution using the electron spin resonance.

Achieving time-domain control of quantum states with atomic-scale spatial resolution in nanostructures is a long-term goal in quantum nanoscience and spintronics. Here, we demonstrate coherent spin rotations of individual atoms on a surface at the nanosecond time scale, using an all-electric scheme in a scanning tunneling microscope (STM). By modulating the atomically confined magnetic interaction between the STM tip and surface atoms, we drive quantum Rabi oscillations between spin-up and spin-down states in as little as ~20 nanoseconds. Ramsey fringes and spin echo signals allow us to understand and improve quantum coherence. We further demonstrate coherent operations on engineered atomic dimers. The coherent control of spins arranged with atomic precision provides a solid-state platform for quantum-state engineering and simulation of many-body systems.