Many-body entanglement is often created through system evolution, aided by non-linear interactions between the constituting particles. The very dynamics, however, can also lead to fluctuations and degradation of the entanglement if the interactions cannot be controlled. Here, we demonstrate neardeterministic generation of an entangled twin-Fock condensate of ∼ 11000 atoms by driving a 87 Rb Bose-Einstein condensate undergoing spin mixing through two consecutive quantum phase transitions (QPTs). We directly observe number squeezing of 10.7 ± 0.6 dB and normalized collective spin length of 0.99 ± 0.01. Together, these observations allow us to infer an entanglementenhanced phase sensitivity of ∼ 6 dB beyond the standard quantum limit and an entanglement breadth of ∼ 910 atoms. Our work highlights the power of generating large-scale useful entanglement by taking advantage of the differ-1

We adopt a global optimization method to predict two-dimensional (2D) nanostructures through the particle-swarm optimization (PSO) algorithm. By performing PSO simulations, we predict new stable structures of 2D boron-carbon (B-C) compounds for a wide range of boron concentrations. Our calculations show that: (1) All 2D B-C compounds are metallic except for BC(3) which is a magic case where the isolation of carbon six-membered ring by boron atoms results in a semi-conducting behavior. (2) For C-rich B-C compounds, the most stable 2D structures can be viewed as boron doped graphene structures, where boron atoms typically form 1D zigzag chains except for BC(3) in which boron atoms are uniformly distributed. (3) The most stable 2D structure of BC has alternative carbon and boron ribbons with strong in-between B-C bonds, which possesses a high thermal stability above 2000 K. (4) For B-rich 2D B-C compounds, there is a novel planar-tetracoordinate carbon motif with an approximate C(2)(v) symmetry.

Interferometry is a paradigm for most precision measurements. Using N uncorrelated particles, the achievable precision for a two-mode (two-path) interferometer is bounded by the standard quantum limit (SQL), [Formula: see text], due to the discrete (quanta) nature of individual measurements. Despite being a challenging benchmark, the two-mode SQL has been approached in a number of systems, including the Laser Interferometer Gravitational-Wave Observatory and today's best atomic clocks. For multimode interferometry, the SQL becomes [Formula: see text] using modes. Higher precision can also be achieved using entangled particles such that quantum noises from individual particles cancel out. In this work, we demonstrate an interferometric precision of [Formula: see text] dB beyond the three-mode SQL, using balanced spin-1 (three-mode) Dicke states containing thousands of entangled atoms. The input quantum states are deterministically generated by controlled quantum phase transition and exhibit close to ideal quality. Our work shines light on the pursuit of quantum metrology beyond SQL.

In this work we model and realize stimulated Raman adiabatic passage (STIRAP) in the diatomic 23 Na 40 K molecule from weakly bound Feshbach molecules to the rovibronic ground state via the |v d = 5, J = Ω = 1 excited state in the d 3 Π electronic potential. We demonstrate how to set up a quantitative model for polar molecule production by taking into account the rich internal structure of the molecules and the coupling laser phase noise. We find excellent agreement between the model predictions and the experiment, demonstrating the applicability of the model in the search of an ideal STIRAP transfer path. In total we produce 5000 fermionic groundstate molecules. The typical phase-space density of the sample is 0.03 and induced dipole moments of up to 0.54 Debye could be observed.Dipolar quantum gases allow for the realization of intriguing new quantum many-body systems and associated phenomena due to their anisotropic and long-range interactions. Among these are the roton driven fluid to crystalline quantum phase transition [1], dipolar droplet formation [2,3], insulators with fractional filling and supersolid phases of dipoles in optical lattices [4] to name only a few. Ultracold polar molecules promise particularly large dipolar interactions due to their large dipole moments.The standard procedure for creating molecules at high phase-space density starts with a mixture of two atomic species close to quantum degeneracy. The two species are then initially adiabatically associated into a weakly bound Feshbach molecular state |F B [5]. From there they can be transferred into the final, electronic, vibrational and rotational (rovibronic) ground state using stimulated Raman adiabatic passage (STIRAP) [6,7]. This last step involves coupling the initial and final state to a common intermediate, electronically excited molecular state. Both |F B and the intermediate state need to be chosen with care in order to allow for a high efficiency in the transfer and thus to preserve the phase space density of the ultracold mixture. This approach has been applied successfully to dipolar KRb [8] to the ground state compared to the STIRAP scheme employed in [11]. We develop a Hamiltonian model to describe the adiabatic transfer in all required details to achieve a quantitative description. In addition to the molecular structure analysis done for different bialkali systems [14,15] we include the complex light coupling into the analysis. This results in a multi-level, crosscoupled model that is intimately related to the work of the Bergmann group on STIRAP in multilevel systems [16] but is specific to the alkali-alkali molecule formation. We investigate how to maximize the STIRAP transfer efficiency for a given intermediate state manifold by optimizing pulse durations and one-photon detuning. We find excellent agreement between simulation and experiment. Finally, we demonstrate ground state molecule creation with a large electric dipole moment of up to 0.54 Debye. I. MOLECULAR LEVEL STRUCTURE AND HAMILTONIAN MODELIn our model we us...

We report the observation of synthesized spin-orbit coupling (SOC) for ultracold spin-1 87Rb atoms. Different from earlier experiments where a one dimensional (1D) atomic SOC of pseudo-spin-1/2 is synthesized with Raman laser fields, the scheme we demonstrate employs a gradient magnetic field (GMF) and ground-state atoms, thus is immune to atomic spontaneous emission. The strength of SOC we realize can be tuned by changing the modulation amplitude of the GMF, and the effect of the SOC is confirmed through the studies of: 1) the collective dipole oscillation of an atomic condensate in a harmonic trap after the synthesized SOC is abruptly turned on; and 2) the minimum energy state at a finite adiabatically adjusted momentum when SOC strength is slowly ramped up. The condensate coherence is found to remain very good after driven by modulating GMFs. Our scheme presents an alternative means for studying interacting many-body systems with synthesized SOC.