Optical Modification of 2D Materials: Methods and Applications.

2D materials are under extensive research due to their remarkable properties suitable for various optoelectronic, photonic, and biological applications, yet their conventional fabrication methods are typically harsh and cost-ineffective. Optical modification is demonstrated as an effective and scalable method for accurate and local in situ engineering and patterning of 2D materials in ambient conditions. This review focuses on the state of the art of optical modification of 2D materials and their applications.

Single-domain Bose condensate magnetometer achieves energy resolution per bandwidth below ℏ.

We present a magnetic sensor with energy resolution per bandwidth [Formula: see text] We show how a Rb single-domain spinor Bose-Einstein condensate, detected by nondestructive Faraday rotation probing, achieves single-shot low-frequency magnetic sensitivity of 72(8) fT measuring a volume [Formula: see text] for 3.5 s, and thus, [Formula: see text] We measure experimentally the condensate volume, spin coherence time, and readout noise and use phase space methods, backed by three-dimensional mean-field simulations, to compute the spin noise. Contributions to the spin noise include one-body and three-body losses and shearing of the projection noise distribution, due to competition of ferromagnetic contact interactions and quadratic Zeeman shifts.

Phase-matching-induced near-chirp-free solitons in normal-dispersion fiber lasers.

Direct generation of chirp-free solitons without external compression in normal-dispersion fiber lasers is a long-term challenge in ultrafast optics. We demonstrate near-chirp-free solitons with distinct spectral sidebands in normal-dispersion hybrid-structure fiber lasers containing a few meters of polarization-maintaining fiber. The bandwidth and duration of the typical mode-locked pulse are 0.

An electron turnstile for frequency-to-power conversion.

Single-electron transport relates an operation frequency f to the emitted current I through the electron charge e as I = ef (refs. ). Similarly, direct frequency-to-power conversion (FPC) links both quantities through a known energy.

Switchable Photoresponse Mechanisms Implemented in Single van der Waals Semiconductor/Metal Heterostructure.

van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been extensively studied for functional applications, and most of the reported devices work with sole mechanism. The emerging metallic 2D materials provide us new options for building functional vdW heterostructures via rational band engineering design. Here, we investigate the vdW semiconductor/metal heterostructure built with 2D semiconducting InSe and metallic 1T-phase NbTe, whose electron affinity and work function almost exactly align.

Tunable Quantum Tunneling through a Graphene/BiSe Heterointerface for the Hybrid Photodetection Mechanism.

Graphene-based van der Waals heterostructures are promising building blocks for broadband photodetection because of the gapless nature of graphene. However, their performance is mostly limited by the inevitable trade-off between low dark current and photocurrent generation. Here, we demonstrate a hybrid photodetection mode based on the photogating effect coupled with the photovoltaic effect via tunable quantum tunneling through the unique graphene/BiSe heterointerface.

Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation.

Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper.

Probing Electronic States in Monolayer Semiconductors through Static and Transient Third-Harmonic Spectroscopies.

Electronic states and their dynamics are of critical importance for electronic and optoelectronic applications. Here, various relevant electronic states in monolayer MoS , such as multiple excitonic Rydberg states and free-particle energy bands are probed with a high relative contrast of up to ≥200 via broadband (from ≈1.79 to 3.

Self-Calibrating Superconducting Pair-Breaking Detector.

We propose and experimentally demonstrate a self-calibrating detector of Cooper pair depairing in a superconductor based on a mesoscopic superconducting island coupled to normal metal leads. On average, exactly one electron passes through the device per broken Cooper pair, independent of the absorber volume, device, or material parameters. The device operation is explained by a simple analytical model and verified with numerical simulations in quantitative agreement with experiment.

Critical current fluctuations in graphene Josephson junctions.

We have studied 1/f noise in critical current [Formula: see text] in h-BN encapsulated monolayer graphene contacted by NbTiN electrodes. The sample is close to diffusive limit and the switching supercurrent with hysteresis at Dirac point amounts to [Formula: see text] nA. The low frequency noise in the superconducting state is measured by tracking the variation in magnitude and phase of a reflection carrier signal [Formula: see text] at 600-650 MHz.

Enhancing SiN Waveguide Nonlinearity with Heterogeneous Integration of Few-Layer WS.

The heterogeneous integration of low-dimensional materials with photonic waveguides has spurred wide research interest. Here, we report on the experimental investigation and the numerical modeling of enhanced nonlinear pulse broadening in silicon nitride waveguides with the heterogeneous integration of few-layer WS. After transferring a few-layer WS flake of ∼14.

Electrical Low-Frequency 1/ Noise Due to Surface Diffusion of Scatterers on an Ultra-low-Noise Graphene Platform.

Low-frequency 1/  noise is ubiquitous, even in high-end electronic devices. Recently, it was found that adsorbed O molecules provide the dominant contribution to flux noise in superconducting quantum interference devices. To clarify the basic principles of such adsorbate noise, we have investigated low-frequency noise, while the mobility of surface adsorbates is varied by temperature.

Giant All-Optical Modulation of Second-Harmonic Generation Mediated by Dark Excitons.

All-optical control of nonlinear photonic processes in nanomaterials is of significant interest from a fundamental viewpoint and with regard to applications ranging from ultrafast data processing to spectroscopy and quantum technology. However, these applications rely on a high degree of control over the nonlinear response, which still remains elusive. Here, we demonstrate giant and broadband all-optical ultrafast modulation of second-harmonic generation (SHG) in monolayer transition-metal dichalcogenides mediated by the modified excitonic oscillation strength produced upon optical pumping.

Giant anisotropic photonics in the 1D van der Waals semiconductor fibrous red phosphorus.

A confined electronic system can host a wide variety of fascinating electronic, magnetic, valleytronic and photonic phenomena due to its reduced symmetry and quantum confinement effect. For the recently emerging one-dimensional van der Waals (1D vdW) materials with electrons confined in 1D sub-units, an enormous variety of intriguing physical properties and functionalities can be expected. Here, we demonstrate the coexistence of giant linear/nonlinear optical anisotropy and high emission yield in fibrous red phosphorus (FRP), an exotic 1D vdW semiconductor with quasi-flat bands and a sizeable bandgap in the visible spectral range.

Ultrahigh Convergent Thermal Conductivity of Carbon Nanotubes from Comprehensive Atomistic Modeling.

Anomalous heat transport in one-dimensional nanostructures, such as nanotubes and nanowires, is a widely debated problem in condensed matter and statistical physics, with contradicting pieces of evidence from experiments and simulations. Using a comprehensive modeling approach, comprised of lattice dynamics and molecular dynamics simulations, we proved that the infinite length limit of the thermal conductivity of a (10,0) single-wall carbon nanotube is finite but this limit is reached only for macroscopic lengths due to a thermal phonon mean free path of several millimeters. Our calculations showed that the extremely high thermal conductivity of this system at room temperature is dictated by quantum effects.

Broadband Plasmon-Enhanced Four-Wave Mixing in Monolayer MoS.

Two-dimensional transition-metal dichalcogenide monolayers have remarkably large optical nonlinearity. However, the nonlinear optical conversion efficiency in monolayer transition-metal dichalcogenides is typically low due to small light-matter interaction length at the atomic thickness, which significantly obstructs their applications. Here, for the first time, we report broadband (up to ∼150 nm) enhancement of optical nonlinearity in monolayer MoS with plasmonic structures.

Multicore Assemblies from Three-Component Linear Homo-Copolymer Systems: A Coarse-Grained Modeling Study.

Multicore polymer micelles and aggregates are assemblies that contain several cores. The dual-length-scale compartmentalized solvophobic-solvophilic molecular environment makes them useful for, e.g.

Quantum mechanics-free subsystem with mechanical oscillators.

Quantum mechanics sets a limit for the precision of continuous measurement of the position of an oscillator. We show how it is possible to measure an oscillator without quantum back-action of the measurement by constructing one effective oscillator from two physical oscillators. We realize such a quantum mechanics-free subsystem using two micromechanical oscillators, and show the measurements of two collective quadratures while evading the quantum back-action by 8 decibels on both of them, obtaining a total noise within a factor of 2 of the full quantum limit.

Inverse Faraday Effect for Superconducting Condensates.

The Cooper pairs in superconducting condensates are shown to acquire a temperature-dependent dc magnetic moment under the effect of the circularly polarized electromagnetic radiation. The mechanisms of this inverse Faraday effect are investigated within the simplest version of the phenomenological dynamic theory for superfluids, namely, the time-dependent Ginzburg-Landau (GL) model. The light-induced magnetic moment is shown to be strongly affected by the nondissipative oscillatory contribution to the superconducting order parameter dynamics, which appears due to the nonzero imaginary part of the GL relaxation time.

Collision Models Can Efficiently Simulate Any Multipartite Markovian Quantum Dynamics.

We introduce the multipartite collision model, defined in terms of elementary interactions between subsystems and ancillas, and show that it can simulate the Markovian dynamics of any multipartite open quantum system. We develop a method to estimate an analytical error bound for any repeated interactions model, and we use it to prove that the error of our scheme displays an optimal scaling. Finally, we provide a simple decomposition of the multipartite collision model into elementary quantum gates, and show that it is efficiently simulable on a quantum computer according to the dissipative quantum Church-Turing theorem, i.

Quantum Speed Limit and Divisibility of the Dynamical Map.

The quantum speed limit (QSL) is the theoretical lower limit of the time for a quantum system to evolve from a given state to another one. Interestingly, it has been shown that non-Markovianity can be used to speed-up the dynamics and to lower the QSL time, although this behaviour is not universal. In this paper, we further carry on the investigation on the connection between QSL and non-Markovianity by looking at the effects of P- and CP-divisibility of the dynamical map to the quantum speed limit.

Time and classical equations of motion from quantum entanglement via the Page and Wootters mechanism with generalized coherent states.

We draw a picture of physical systems that allows us to recognize what "time" is by requiring consistency with the way that time enters the fundamental laws of Physics. Elements of the picture are two non-interacting and yet entangled quantum systems, one of which acting as a clock. The setting is based on the Page and Wootters mechanism, with tools from large-N quantum approaches.

Thermodynamics of Gambling Demons.

We introduce and realize demons that follow a customary gambling strategy to stop a nonequilibrium process at stochastic times. We derive second-law-like inequalities for the average work done in the presence of gambling, and universal stopping-time fluctuation relations for classical and quantum nonstationary stochastic processes. We test experimentally our results in a single-electron box, where an electrostatic potential drives the dynamics of individual electrons tunneling into a metallic island.

Electronic transport in molecular junctions: The generalized Kadanoff-Baym ansatz with initial contact and correlations.

The generalized Kadanoff-Baym ansatz (GKBA) offers a computationally inexpensive approach to simulate out-of-equilibrium quantum systems within the framework of nonequilibrium Green's functions. For finite systems, the limitation of neglecting initial correlations in the conventional GKBA approach has recently been overcome [Karlsson et al., Phys.

Path to European quantum unicorns.

Quantum computing holds the potential to deliver great economic prosperity to the European Union (EU). However, the creation of successful business in the field is challenging owing to the required extensive investments into postdoctoral-level workforce and sophisticated infrastructure without an existing market that can financially support these operations. This commentary paper reviews the recent efforts taken in the EU to foster the quantum-computing ecosystem together with its current status.