We investigate the conditions under which a set of multipartite nonlocal correlations can describe the distributions achievable by distant parties conducting experiments in a consistent universe. Several questions are posed, such as: are all such sets "nested", i.e., contained into one another? Are they discrete or do they form a continuum? How many of them are supraquantum? Are there non-trivial polytopes among them?We answer some of these questions or relate them with established conjectures in complexity theory by introducing a "zoo" of physically consistent sets which can be characterized efficiently via either linear or semidefinite programming. As a bonus, we use the zoo to derive, for the first time, concrete impossibility results in nonlocality distillation.

Emitter ensembles interact collectively with the radiation field. In the case of a one-dimensional array of atoms near a nanofiber, this collective light-matter interaction does not only lead to an increased photon coupling to the guided modes within the fiber, but also to a drastic enhancement of the chirality in the photon emission. We show that near-perfect chirality is already achieved for moderately-sized ensembles, containing 10 to 15 atoms. This is of importance for developing an efficient interface between atoms and waveguide structures with unidirectional coupling, with applications in quantum computing and communication such as the development of non-reciprocal photon devices or quantum information transfer channels.

for the Pediatric Readiness Study Group IMPORTANCE There is substantial variability among emergency departments (EDs) in their readiness to care for acutely ill and injured children, including US trauma centers. While high ED pediatric readiness is associated with improved in-hospital survival among children treated at trauma centers, the association between high ED readiness and long-term outcomes is unknown.OBJECTIVE To evaluate the association between ED pediatric readiness and 1-year survival among injured children presenting to 146 trauma centers. DESIGN, SETTING, AND PARTICIPANTSIn this retrospective cohort study, injured children younger than 18 years who were residents of 8 states with admission, transfer to, or injury-related death at one of 146 participating trauma centers were included. Children cared for in and outside their state of residence were included. Subgroups included those with an Injury Severity Score (ISS) of 16 or more; any Abbreviated Injury Scale (AIS) score of 3 or more; head AIS score of 3 or more; and need for early critical resources. Data were collected from January 2012 to December 2017, with follow-up to December 2018. Data were analyzed from January to July 2021.EXPOSURES ED pediatric readiness for the initial ED, measured using the weighted Pediatric Readiness Score (wPRS; range, 0-100) from the 2013 National Pediatric Readiness Project assessment.MAIN OUTCOMES AND MEASURES Time to death within 365 days. RESULTSOf 88 071 included children, 30 654 (34.8%) were female; 2114 (2.4%) were Asian, 16 730 (10.0%) were Black, and 49 496 (56.2%) were White; and the median (IQR) age was 11 (5-15) years. A total of 1974 (2.2%) died within 1 year of the initial ED visit, including 1768 (2.0%) during hospitalization and 206 (0.2%) following discharge. Subgroups included 12 752 (14.5%) with an ISS of 16 or more, 28 402 (32.2%) with any AIS score of 3 or more, 13 348 (15.2%) with a head AIS of 3 or more, and 9048 (10.3%) requiring early critical resources. Compared with EDs in the lowest wPRS quartile (32-69), children cared for in the highest wPRS quartile (95-100) had lower hazard of death to 1 year (adjusted hazard ratio [aHR], 0.70; 95% CI, 0.56-0.88). Supplemental analyses removing early deaths had similar results (aHR, 0.75; 95% CI, 0.56-0.996). Findings were consistent across subgroups and multiple sensitivity analyses. CONCLUSIONS AND RELEVANCEChildren treated in high-readiness trauma center EDs after injury had a lower risk of death that persisted to 1 year. High ED readiness is independently associated with long-term survival among injured children.

Spontaneous emission from excitonic transitions in InAs/GaAs quantum dots embedded in photonic crystal waveguides at 5 K into non-guided and guided modes is determined by direct hyperspectral imaging. This enables measurement of the absolute coupling efficiency into the guided modes, the beta factor, directly, without assumptions on decay rates used previously. Notably, we found beta factors above 90% over a wide spectral range of 40 meV in the fast light regime, reaching a maximum of (99 ± 1)%. We measure the directional emission of the circularly polarized transitions in a magnetic field into counter-propagating guided modes, to deduce the mode circularity at the quantum dot sites. We find that points of high directionality, up to 97%, correlate with a reduced beta factor consistent with their positions away from the mode field antinode. By comparison with calibrated finite-difference time-domain simulations, we use the emission energy, mode circularity and beta factor to estimate the quantum dot position inside the photonic crystal waveguide unit cell.

Unidirectional (chiral) emission of light from a circular dipole emitter into a waveguide is only possible at points of perfect circular polarisation (C points), with elliptical polarisations yielding a lower directional contrast. However, there is no need to restrict engineered systems to circular dipoles, and with an appropriate choice of dipole unidirectional emission is possible for any elliptical polarization. Using elliptical dipoles, rather than circular, typically increases the size of the area suitable for chiral interactions (in an exemplary mode by a factor ∼ 30), while simultaneously increasing coupling efficiencies. We propose illustrative schemes to engineer the necessary elliptical transitions in both atomic systems and quantum dots.

We present slow-light photonic crystal waveguide designs that provide a ×8.6 improvement of the local density of optical states at a fully chiral point over previous designs.

We explore the dissipative dynamics of nonlinearly driven oscillator systems tuned to resonances where multiple excitations are generated. Such systems are readily realised in circuit QED systems combining Josephson junctions with a microwave cavity and a drive achieved either through flux or voltage bias. For resonances involving three or more photons the system undergoes a sequence of two closely spaced dynamical transitions (the first one discontinuous and the second continuous) as the driving is increased leading to steady states that form complex periodic structures in phase space. In the vicinity of the transitions the system displays interesting bistable behaviour: we find that coherent effects can lead to surprising oscillations in the weight of the different dynamical states in the steady state of the system with increasing drive. We show that the dynamics is well-described by a simple effective rate model with transitions between states localised at different points in the phase space crystal. The oscillations in the weights of the dynamical states is reflected in corresponding oscillations in a time-scale that describes transitions between the states.

Photonic crystal waveguides are known to support C-points -point-like polarisation singularities with local chirality. Such points can couple with dipole-like emitters to produce highly directional emission, from which spin-photon entanglers can be built. Much is made of the promise of using slowlight modes to enhance this light-matter coupling. Here we explore the transition from travelling to standing waves for two different photonic crystal waveguide designs. We find that time-reversal symmetry and the reciprocal nature of light places constraints on using C-points in the slow-light regime. We observe two distinctly different mechanisms through which this condition is satisfied in the two waveguides. In the waveguide designs we consider, a modest group-velocity of vg ≈ c/10 is found to be the optimum for slow-light coupling to the C-points.