Controlling quantum matter with light offers a promising route to dynamically tune its many-body properties, ranging from band topology1,2 to superconductivity3. However, achieving such optical control for strongly correlated electron systems in the steady state has remained elusive. Here we demonstrate optical switching of the spin-valley degree of freedom of itinerant ferromagnets in twisted MoTe2 (t-MoTe2) homobilayers. This system uniquely features flat valley-contrasting Chern bands and exhibits a range of strongly correlated phases at various moiré lattice fillings, including Chern insulators and ferromagnetic metals4-7. We show that the spin-valley orientation of all of these phases can be dynamically reversed by resonantly exciting the exciton-polaron8 transitions with circularly polarized light. These findings not only provide direct evidence for non-thermal optical switching of a ferromagnetic spin state at zero magnetic field but also demonstrate the possibility of dynamical control over a topological order parameter, paving the way for optical generation of chiral edge modes and topological quantum circuits.
Controlling precursor reactivity through ligand design remains a central challenge in the colloidal synthesis of III-V quantum dots (QDs). In particular, InSb QDs have been difficult to access due to hazardous metal-hydride reductants and limited precursor availability. Here, we report a metal-reductant-free route employing tris(dimethylamino)phosphine [P(NMe2)(3)], whose function as a reductant or a P(-III) source is determined by the coordination environment of SbCl3. When Sb-oleylamine (OlNH(2)) complexes are used, P(NMe2)(3) reduces both Sb and In precursors, producing phase-pure InSb QDs. In contrast, Sb-trioctylphosphine (TOP) complexes undergo partial Sb(+III) reduction via electrons released from TOP oxidation, while P(NMe2)(3) simultaneously reduces In and generates P(-III) species, enabling controlled formation of alloyed InP1-xSbx QDs (0.6 <= x < 1). P-31 NMR and EXAFS analyses reveal that the Sb-TOP complex exists in a dynamic chloride-phosphine equilibrium, which governs P(-III) availability and reaction selectivity. This mechanistic insight demonstrates that ligand coordination can be leveraged to modulate precursor reactivity, selectively direct reduction pathways, and achieve controlled alloying in colloidal III-V QDs. The resulting QDs exhibit sharp excitonic absorption and band-edge emission in the short-wavelength infrared (SWIR) region, bridging the previously inaccessible spectral gap between InP and InSb. Beyond InSb and InP1-xSbx, these findings establish a general design principle: dynamic ligand environments can be exploited to tune reactivity, composition, and alloy formation in colloidal semiconductors. This work thus provides a safe, high-yielding, mechanistically rational strategy for Sb-based III-V QDs and lays the foundation for extending optoelectronic functionality through precise precursor engineering.
Optically active defects in hexagonal boron nitride (hBN) have become amongst the most attractive single-photon emitters in the solid state, owing to their high-quality photophysical properties, combined with the unlimited possibilities of integration offered by the host two-dimensional material. In particular, the B centres, with their narrow linewidth, low wavelength spread and controllable positioning, have raised a particular interest for integrated quantum photonics. However, to date, either their excitation or their detection has been performed non-resonantly due to the difficulty of rejecting the backreflected laser light at the same wavelength, thereby preventing to take full benefit from their high coherence in quantum protocols. Here, we make use of a narrow-linewidth emitter integrated in a hybrid metal-dielectric structure to implement crossed-polarisation laser rejection. This allows us to observe resonantly scattered photons, with associated experimental signatures of optical coherence in both continuous-wave (cw) and pulsed regimes, respectively the Mollow triplet and Hong-Ou-Mandel interference from zero-phonon-line emission. The measured two-photon interference visibility of 0.92 demonstrates the potential of B centres in hBN for applications to integrated quantum information.
Black-box optimization (BBO) is used in materials design, drug discovery, and hyperparameter tuning in machine learning. The world is experiencing several of these problems. In this review, a factorization machine with quantum annealing or with quadratic-optimization annealing (FMQA) algorithm to realize fast computations of BBO using Ising machines (IMs) is discussed. The FMQA algorithm uses a factorization machine (FM) as a surrogate model for BBO. The FM model can be directly transformed into a quadratic unconstrained binary optimization model that can be solved using IMs. This makes it possible to optimize the acquisition function in BBO, which is a difficult task using conventional methods without IMs. Consequently, it has the advantage of handling large BBO problems. To be able to perform BBO with the FMQA algorithm immediately, we introduce the FMQA algorithm along with Python packages to run it. In addition, we review examples of applications of the FMQA algorithm in various fields, including physics, chemistry, materials science, and social sciences. These successful examples include binary and integer optimization problems, as well as more general optimization problems involving graphs, networks, and strings, using a binary variational autoencoder. We believe that BBO using the FMQA algorithm will become a key technology in IMs including quantum annealers.
Position exchange of non-Abelian anyons affects the quantum state of their system in a topologically protected way1. Their expected manifestations in even-denominator fractional quantum Hall (FQH) systems offer the opportunity to directly study their unique statistical properties in interference experiments2. Here we present the observation of coherent Aharonov-Bohm interference at two even-denominator states in high-mobility bilayer-graphene-based van der Waals (vdW) heterostructures by using the Fabry-Pérot interferometry technique. Operating the interferometer at a constant filling factor, we observe an oscillation period corresponding to two flux quanta inside the interference loop, ΔΦ = 2Φ0, at which the interference does not carry signatures of non-Abelian statistics. The absence of the expected periodicity of ΔΦ = 4Φ0 may indicate that the interfering quasiparticles carry the charge e * = 1 2 e or that interference of e * = 1 4 e quasiparticles is thermally smeared. Notably, at two hole-conjugate states, we also observe oscillation periods of half the expected value, indicating interference of e * = 2 3 e quasiparticles instead of e * = 1 3 e . To investigate statistical phase contributions, we operated the Fabry-Pérot interferometer (FPI) with controlled deviations of the filling factor, thereby introducing fractional quasiparticles inside the interference loop. The resulting changes to the interference patterns at both half-filled states indicate that the extra bulk quasiparticles carry the fundamental charge e * = 1 4 e , as expected for non-Abelian anyons.
