Nature Physics最新文献

Gauge theories constitute the basis of the Standard Model and provide useful descriptions of various phenomena in condensed matter. Realizing gauge theories on tunable tabletop quantum devices such as cold-atom quantum simulators offers the possibility to study their dynamics from first principles and to probe effects that are out of reach of dedicated particle colliders, such as deviations from gauge invariance. These quantum simulators can potentially provide insights into high-energy and nuclear physics questions, while also serving as a versatile tool for the exploration of topological phases and ergodicity-breaking mechanisms relevant to low-energy many-body physics. Recent years have seen substantial progress in the implementation of (1 + 1)D Abelian gauge theories using ultracold atoms. In this Review, we chronicle these advances, highlighting key developments in stabilizing gauge invariance and scaling up from basic building blocks to large-scale realizations where gauge-theory phenomena can be probed. We offer an outlook on future directions and the requirements for advancing this technology to the next level.

Understanding thermodynamical measurement noise is of central importance for electrical and optical precision measurements. These range from semiconductor sensors, in which the Brownian motion of charge carriers poses limits, to optical reference cavities for atomic clocks or gravitational wave detection, which are limited by thermo-refractive and thermo-elastic noise. Here we find that charge-carrier density fluctuations give rise to a noise process in electro-optic photonic integrated circuits. We show that the noise exhibited by lithium niobate and lithium tantalate photonic integrated microresonators feature a frequency scaling to the power of −1.2, deviating from thermo-refractive noise theory. This noise is consistent with thermodynamical charge noise, which leads to electrical field fluctuations that are transduced via the strong Pockels effects of electro-optic materials. Our results establish electrical Johnson–Nyquist noise as the fundamental limitation for electro-optic integrated photonics, crucial for determining performance limits for both classical and quantum devices.

High-dimensional quantum systems are a valuable resource for quantum information processing. They can be used to encode error-correctable logical qubits, which has been demonstrated using continuous-variable states in microwave cavities or the motional modes of trapped ions. For example, high-dimensional systems can be used to realize ‘Schrödinger cat’ states, which are superpositions of widely displaced coherent states that can be used to illustrate quantum effects at large scales. Recent proposals have suggested encoding qubits in high-spin atomic nuclei, which are finite-dimensional systems that can host hardware-efficient versions of continuous-variable codes. Here we demonstrate the creation and manipulation of Schrödinger cat states using the spin-7/2 nucleus of an antimony atom embedded in a silicon nanoelectronic device. We use a multi-frequency control scheme to produce spin rotations that preserve the symmetry of the qudit, and we constitute logical Pauli operations for qubits encoded in the Schrödinger cat states. Our work demonstrates the ability to prepare and control non-classical resource states, which is a prerequisite for applications in quantum information processing and quantum error correction, using our scalable, manufacturable semiconductor platform.

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.