Nature Physics最新文献

In recent years, a self-consistent optical thermodynamic framework has emerged that offers a systematic methodology to understand, harness and exploit the complex collective dynamics of multimode nonlinear systems. These developments now allow consideration of a series of long-standing problems in optics, including the prospect of funnelling the entire power flowing in a multimode system into its ground state, for which no methodology currently exists. Here we demonstrate an all-optical Joule–Thomson expansion process mediated by photon–photon interactions whereby the temperature of the optical gas drops abruptly to zero. Our experiments in various configurations of coupled multicore nonlinear waveguide arrangements illustrate how light undergoing expansion-induced cooling can be channelled from arbitrary input states into the fundamental mode with near-unity efficiency. We show that the stability of the post-expansion state is ensured through an irreversible process of energy conversion. The all-optical thermodynamic phenomena explored in this study may enable innovative techniques where various uncorrelated but identical sources are merged into a unified spatially coherent state, offering a route for direct beam combining.

Gauge theories describe the fundamental forces in the standard model of particle physics and play an important role in condensed-matter physics. The constituents of gauge theories, for example, charged matter and electric gauge field, are governed by local gauge constraints, which lead to key phenomena such as the confinement of particles that are not fully understood. In this context, quantum simulators may address questions that are challenging for classical methods. Although engineering gauge constraints is highly demanding, recent advances in quantum computing are beginning to enable digital quantum simulations of gauge theories. Here we simulate confinement dynamics in a ({{mathbb{Z}}}_{2}) lattice gauge theory on a superconducting quantum processor. Tuning a term that couples only to the electric field produces confinement of charges, a manifestation of the tight bond that the gauge constraint generates between both. Moreover, we show how a modification of the gauge constraint from ({{mathbb{Z}}}_{2}) towards U(1) symmetry freezes the system dynamics. Our work illustrates the restriction that the underlying gauge constraint imposes on the dynamics of a lattice gauge theory, showcases how gauge constraints can be modified and protected, and promotes the study of other models governed by multibody interactions.

Helices and spirals, prevalent across various physical systems, play a crucial role in characterizing symmetry, describing dynamics and enabling unique functionalities, all stemming from their inherent simplicity and chiral nature. Helical excitations on quantized vortices, referred to as Kelvin waves, are one example of such a physical system. Kelvin waves play a vital role in energy dissipation within inviscid quantum fluids. However, deliberately exciting Kelvin waves has proven to be challenging. Here we introduce a controlled method for exciting Kelvin waves on a quantized vortex in superfluid helium-4. We used a charged nanoparticle that oscillates when driven by a time-varying electric field to stimulate Kelvin waves on the vortex. Confirmation of the helical nature of Kelvin waves was achieved through three-dimensional image reconstruction, which provided visual evidence of their complex dynamics. Additionally, we determined the dispersion relation and the phase velocity of the Kelvin wave and identified the vorticity direction, thus enhancing our understanding of quantum fluid behaviour. This work elucidates the dynamics of Kelvin waves and initiates an approach for manipulating and observing quantized vortices in three dimensions, thereby opening avenues for exploring quantum fluidic systems.

Flat bands in condensed matter systems can host emergent states of matter, from insulating states in twisted bilayer graphene to fractionalized excitations in frustrated magnets and quantum Hall materials. A key phenomenon in certain flat-band systems is Aharonov–Bohm caging, where particles become localized due to destructive interference caused by gauge fields. Here we report on the experimental realization of highly tunable flat-band models populated by strongly interacting Rydberg atoms. By employing synthetic dimensions, we engineer a flat-band rhombic lattice with twisted boundaries and explore the control of Aharonov–Bohm caging during non-equilibrium dynamics through a tunable gauge field. Microscopic measurements of Rydberg pairs reveal the interaction-driven breakdown of Aharonov–Bohm caging in the limit of strong dipolar interactions, where lattice bands mix. In the limit of weak interactions, where caging persists, we observe effective magnetism arising from the interaction-driven mixing of degenerate flat-band states. These observations offer insights into emergent phenomena in synthetic quantum materials and expand our understanding of quantum many-body physics in engineered lattice systems.

Understanding the mechanical properties of soft jammed solids that consist of densely packed particles, such as foams and emulsions, requires insights into the microscopic origins of linear viscoelasticity—how a solid responds to an infinitesimal deformation. Here we perform microrheology experiments on concentrated emulsions and measure the storage and loss moduli for a wide range of frequencies. We applied a linear response formalism for microrheology to a soft sphere model that undergoes the jamming transition. We find that the theory quantitatively explains the experiments. Our analysis reveals that the anomalous viscous loss seen in emulsions results from the boson peak, which is a universal vibrational property of amorphous solids and reflects the marginal stability in soft jammed solids. We show that the anomalous viscous loss is universal in systems with various interparticle interactions as it stems from the universal boson peak; it even survives below the jamming density at which thermal fluctuation is pronounced and the dynamics becomes inherently nonlinear.

Gaining control over chemical reactions at the quantum level is a central goal of cold and ultracold chemistry. Here we demonstrate a method for coherently steering the reaction flux across different product spin channels for a three-body recombination process in a cloud of trapped cold atoms. We use a magnetically tunable Feshbach resonance to admix, in a controlled way, a specific spin state to the reacting collision complex. This allows us to control the reaction flux into the admixed spin channel, which can be used to alter the reaction products. We also investigate the influence of an Efimov resonance on the reaction dynamics, observing a global enhancement of three-body recombination without favouring particular reaction channels. Our control scheme can be extended to other reaction processes and could be combined with other methods, such as quantum interference of reaction paths, to achieve further tuning capabilities of few-body reactions.

Although classical thermal machines power industries and modern living, quantum thermal engines have yet to prove their utility. Here, we demonstrate a useful quantum absorption refrigerator formed from superconducting circuits. We use it to cool a transmon qubit to a temperature lower than that achievable with any one available bath, thereby resetting the qubit to an initial state suitable for quantum computing. The process is driven by a thermal gradient and is autonomous, requiring no external feedback. The refrigerator exploits an engineered three-body interaction between the target qubit and two auxiliary qudits. Each auxiliary qudit is coupled to a physical heat bath, realized with a microwave waveguide populated with synthesized quasithermal radiation. If the target qubit is initially fully excited, its effective temperature reaches a steady-state level of approximately 22 mK, lower than what can be achieved by existing state-of-the-art reset protocols. Our results demonstrate that superconducting circuits with propagating thermal fields can be used to experimentally explore quantum thermodynamics and apply it to quantum information-processing tasks.

Counterflow superfluidity is an anomalous quantum phase that was predicted two decades ago in the context of a two-component Bose–Hubbard model. In this phase, although both components exhibit fluidity, their correlated counterflow currents cancel each other out, resulting in the system behaving as an incompressible Mott insulator. However, realizing and identifying this phase experimentally has proven challenging due to the stringent requirements for a single set-up, including defect-free state preparation, minimal heating during coherent manipulations, and spin- and site-resolved detection of the phases. Here, we report on the observation of counterflow superfluidity in a binary Bose mixture in optical lattices. After preparing a low-entropy spin-Mott state by conveying two spin-1/2 bosonic atoms at every single lattice site to form a doublon, we adiabatically drove the system to the counterflow superfluid phase at approximately 1 nK. We observed features of antipair correlations through site- and spin-resolved quantum-gas microscopy in both real and momentum spaces. Finally, we measured long-range off-diagonal spin correlations in the rotated basis, revealing a correlation length approaching the system size. These techniques and observations demonstrated here provide accessibility to Borromean counterfluids.

Spin–orbit torque can drive auto-oscillations of propagating spin-wave modes in nano-constriction spin Hall nano-oscillators. These modes facilitate both long-range coupling and the possibility of controlling their phase, which is a crucial aspect for device application. Here, we demonstrate variable-phase coupling between two nano-constriction spin Hall nano-oscillators and their mutual synchronization driven by propagating spin waves. Using electrical measurements and phase-resolved micro-focused Brillouin light scattering microscopy, we show that the phase of the mutual synchronization can be tuned by modulating the drive current or the applied field. Our micromagnetic simulations explore the phase tunability using voltage gating. Our results advance the capabilities of mutually synchronized spin Hall nano-oscillators and open the possibilities for applications in spin-wave logic-based devices.