Nature Physics最新文献

Quantum networks require quantum nodes with coherent optical interfaces and several stationary qubits. In terms of optical properties, semiconductor quantum dots are highly compelling, but their adoption as quantum nodes has been impaired by the lack of auxiliary qubits. Here we demonstrate that the dense, always-present, nuclear spin ensemble surrounding a gallium arsenide quantum dot can be used as a functional quantum register. We prepared 13,000 host nuclear spins in a single many-body dark state that acts as a logical state of the register. A second logical state is defined as a single nuclear-magnon excitation, enabling controlled quantum-state transfer between an electron spin qubit in the quantum dot and the nuclear magnonic register. Using SWAP gates, we implemented a full write–store–retrieve-read-out protocol with 68.6(4)% raw overall fidelity and a storage time of 130(16) μs, which could be extended to 20 ms or beyond using dynamical decoupling techniques. Our work establishes how many-body physics can add functionality to quantum devices, in this case transforming quantum dots into multi-qubit quantum nodes with deterministic registers.

Photo-excited quantum materials can be driven into thermally inaccessible metastable states that exhibit structural, charge, spin, topological and superconducting orders. Metastable states typically emerge on timescales set by the intrinsic electronic and phononic energy scales, ranging from femtoseconds to picoseconds, and can persist for weeks. Therefore, studies have primarily focused on ultrafast or quasi-static limits, leaving the intermediate time window less explored. Here we reveal a metastable state with broken glide-plane symmetry in photo-doped Ca₂RuO₄ using time-resolved optical second-harmonic generation and birefringence measurements. We find that the metastable state appears long after intralayer antiferromagnetic order has melted and photo-carriers have recombined. Its properties are distinct from all known states in the equilibrium phase diagram and are consistent with intralayer ferromagnetic order. Furthermore, model Hamiltonian calculations reveal that a non-thermal trajectory to this state can be accessed via photo-doping. Our results expand the search space for out-of-equilibrium electronic matter to metastable states emerging at intermediate timescales.

Floquet–Bloch manipulation, achieved by driving a material periodically with a laser pulse, is a method that enables the engineering of electronic and magnetic phases in solids by effectively modifying the structure of their electronic bands. However, the application of Floquet–Bloch manipulation in topological magnetic systems, particularly those with inherent disorder, remains largely unexplored. Here we realize Floquet–Bloch manipulation of the Dirac surface-state mass of the topological antiferromagnet MnBi₂Te₄. Using time- and angle-resolved photoemission spectroscopy, we show that opposite helicities of mid-infrared circularly polarized light result in substantially different Dirac mass gaps in the antiferromagnetic phase, despite the equilibrium Dirac cone being massless. We explain our findings in terms of a Dirac fermion with a random mass. Our results underscore Floquet–Bloch manipulation as a powerful tool for controlling topology, even in the presence of disorder, and for uncovering properties of materials that may elude conventional probes.