Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

We have investigated ion dynamics associated with a dual linear ion trap where ions can be stored in and moved between two distinct locations. Such a trap is a building block for a system to engineer arbitrary quantum states of ion ensembles. Specifically, this trap is the unit cell in a strategy for scalable quantum computing using a series of interconnected ion traps. We have transferred an ion between trap locations 1.2 mm apart in 50 $\mu$s with near unit efficiency ($> 10^{6}$ consecutive transfers) and negligible motional heating, while maintaining internal-state coherence. In addition, we have separated two ions held in a common trap into two distinct traps.

Single crystals of a one-component plasma were observed by optical Bragg diffraction. The plasmas contained 10(5) to 10(6) single-positive beryllium-9 ions (9Be+) at particle densities of 10(8) to 10(9) per cubic centimeter. In approximately spherical plasmas, single body-centered cubic (bcc) crystals or, in some cases, two or more bcc crystals having fixed orientations with respect to each other were observed. In some oblate plasmas, a mixture of bcc and face-centered cubic ordering was seen. Knowledge of the properties of one-component plasma crystals is required for models of white dwarfs and neutron stars, which are believed to contain matter in that form.

Solar steam generation is regarded as a perspective technology, due to its potentials in solar light absorption and photothermal conversion for seawater desalination and water purification. Although lots of steam generation systems have been reported to possess high conversion efficiencies recently, researches of simple, cost-effective, and sustainable materials still need to be done. Here, inspired by natural young sunflower heads’ property increasing the temperature of dish-shaped flowers by tracking the sun, we used 3D-structured carbonized sunflower heads as an effective solar steam generator. The evaporation rate and efficiency of these materials under 1 sun (1 kW m–2) are 1.51 kg m–2 h–1 and 100.4%, respectively, beyond the theoretical limit of 2D materials. This high solar efficiency surpasses all other biomass-based materials ever reported. It is demonstrated that such a high capability is mainly attributed to the 3D-structured top surface, which could reabsorb the lost energy of diffuse reflection and thermal radiation, as well as provide enlarged water/air interface for steam escape. 3D-structured carbonized sunflower heads provide a new method for the future design and fabrication of high-performance photothermal devices.