We report on the first experimental realization of the controlled-not (cnot) quantum gate and entanglement for two individual atoms of different isotopes and demonstrate a negligible cross talk between two atom qubits. The experiment is based on a strong Rydberg blockade for ^{87}Rb and ^{85}Rb atoms confined in two single-atom optical traps separated by 3.8  μm. The raw fidelities of the cnot gate and entanglement are 0.73±0.01 and 0.59±0.03, respectively, without any corrections for atom loss or trace loss. Our work has applications for simulations of many-body systems with multispecies interactions, for quantum computing, and for quantum metrology.

Establishment of symbiosis between certain host plants and nitrogen-fixing bacteria ("rhizobia") depends on type 3 effector proteins secreted via the bacterial type 3 secretion system (T3SS). Here, we report that the open reading frame y4zC of strain NGR234 encodes a novel rhizobial type 3 effector, termed NopT (for nodulation outer protein T). Analysis of secreted proteins from NGR234 and T3SS mutants revealed that NopT is secreted via the T3SS. NopT possessed autoproteolytic activity when expressed in Escherichia coli or human HEK 293T cells. The processed NopT exposed a glycine (G50) to the N terminus, which is predicted to be myristoylated in eukaryotic cells. NopT with a point mutation at position C93, H205, or D220 (catalytic triad) showed strongly reduced autoproteolytic activity, indicating that NopT is a functional protease of the YopT-AvrPphB effector family. When transiently expressed in tobacco plants, proteolytically active NopT elicited a rapid hypersensitive reaction. Arabidopsis plants transformed with nopT showed chlorotic and necrotic symptoms, indicating a cytotoxic effect. Inoculation experiments with mutant derivatives of NGR234 indicated that NopT affected nodulation either positively (Phaseolus vulgaris cv. Yudou No. 1; Tephrosia vogelii) or negatively (Crotalaria juncea). We suggest that NopT-related polymorphism may be involved in evolutionary adaptation of NGR234 to particular host legumes.In root nodules of legumes, symbiotic bacteria ("rhizobia" belonging to the Rhizobiaceae family) reduce N 2 gas into ammonia by the process termed nitrogen fixation. Nodule formation requires specific bacterial signals and determinants (12). Rhizobial nodulation factors (Nod factors) trigger various host responses, including root hair deformation, expression of symbiosis-related host genes, and cortical cell divisions resulting in nodule formation (31, 32). Host-specific nodulation depends also on surface carbohydrates, such as oligosaccharides released from exopolysaccharides, lipopolysaccharides, cyclic ␤-glucans, and K antigens (also named capsular polysaccharides). In Rhizobium sp. strain NGR234, for example, mutants that do not produce exo-oligosaccharides or flavonoid-inducible lipopolysaccharide are unable to establish symbiosis with various host plants (36,48). In addition to these symbiotic determinants, host-specific nodulation depends on proteins secreted via a pilus-like secretory apparatus, the type 3 secretion system (T3SS) of NGR234. Recent data from various laboratories provide evidence that T3SSs of certain rhizobial strains modulate establishment of symbiosis and the efficiency of nitrogen fixation (14,23,25,56).T3SSs from pathogenic bacteria deliver effector proteins (type 3 effectors) into eukaryotic cells to manipulate the host metabolism, e.g., to suppress defense responses. Many reports indicate that type 3 effectors are virulence factors that play a key role in the pathogenesis of humans, animals, and plants (9,20). On the other hand, eukaryotic host cells developed strategies ...