Probing entanglement in a 2D hard-core Bose-Hubbard lattice.

Entanglement and its propagation are central to understanding many physical properties of quantum systems1-3. Notably, within closed quantum many-body systems, entanglement is believed to yield emergent thermodynamic behaviour4-7. However, a universal understanding remains challenging owing to the non-integrability and computational intractability of most large-scale quantum systems. Quantum hardware platforms provide a means to study the formation and scaling of entanglement in interacting many-body systems8-14. Here we use a controllable 4 × 4 array of superconducting qubits to emulate a 2D hard-core Bose-Hubbard (HCBH) lattice. We generate superposition states by simultaneously driving all lattice sites and extract correlation lengths and entanglement entropy across its many-body energy spectrum. We observe volume-law entanglement scaling for states at the centre of the spectrum and a crossover to the onset of area-law scaling near its edges.

Impact of ionizing radiation on superconducting qubit coherence.

Technologies that rely on quantum bits (qubits) require long coherence times and high-fidelity operations1. Superconducting qubits are one of the leading platforms for achieving these objectives2,3. However, the coherence of superconducting qubits is affected by the breaking of Cooper pairs of electrons4-6. The experimentally observed density of the broken Cooper pairs, referred to as quasiparticles, is orders of magnitude higher than the value predicted at equilibrium by the Bardeen-Cooper-Schrieffer theory of superconductivity7-9. Previous work10-12 has shown that infrared photons considerably increase the quasiparticle density, yet even in the best-isolated systems, it remains much higher10 than expected, suggesting that another generation mechanism exists13. Here we provide evidence that ionizing radiation from environmental radioactive materials and cosmic rays contributes to this observed difference. The effect of ionizing radiation leads to an elevated quasiparticle density, which we predict would ultimately limit the coherence times of superconducting qubits of the type measured here to milliseconds. We further demonstrate that radiation shielding reduces the flux of ionizing radiation and thereby increases the energy-relaxation time. Albeit a small effect for today's qubits, reducing or mitigating the impact of ionizing radiation will be critical for realizing fault-tolerant superconducting quantum computers.

Author Correction: Impact of ionizing radiation on superconducting qubit coherence.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Waveguide quantum electrodynamics with superconducting artificial giant atoms.

Models of light-matter interactions in quantum electrodynamics typically invoke the dipole approximation1,2, in which atoms are treated as point-like objects when compared to the wavelength of the electromagnetic modes with which they interact. However, when the ratio between the size of the atom and the mode wavelength is increased, the dipole approximation no longer holds and the atom is referred to as a 'giant atom'2,3. So far, experimental studies with solid-state devices in the giant-atom regime have been limited to superconducting qubits that couple to short-wavelength surface acoustic waves4-10, probing the properties of the atom at only a single frequency. Here we use an alternative architecture that realizes a giant atom by coupling small atoms to a waveguide at multiple, but well separated, discrete locations. This system enables tunable atom-waveguide couplings with large on-off ratios3 and a coupling spectrum that can be engineered by the design of the device. We also demonstrate decoherence-free interactions between multiple giant atoms that are mediated by the quasi-continuous spectrum of modes in the waveguide-an effect that is not achievable using small atoms11. These features allow qubits in this architecture to switch between protected and emissive configurations in situ while retaining qubit-qubit interactions, opening up possibilities for high-fidelity quantum simulations and non-classical itinerant photon generation12,13.

Evolution of 1/f Flux Noise in Superconducting Qubits with Weak Magnetic Fields.

The microscopic description of 1/f magnetic flux noise in superconducting circuits has remained an open question for several decades despite extensive experimental and theoretical investigation. Recent progress in superconducting devices for quantum information has highlighted the need to mitigate sources of qubit decoherence, driving a renewed interest in understanding the underlying noise mechanism(s). Though a consensus has emerged attributing flux noise to surface spins, their identity and interaction mechanisms remain unclear, prompting further study. Here, we apply weak in-plane magnetic fields to a capacitively shunted flux qubit (where the Zeeman splitting of surface spins lies below the device temperature) and study the flux-noise-limited qubit dephasing, revealing previously unexplored trends that may shed light on the dynamics behind the emergent 1/f noise. Notably, we observe an enhancement (suppression) of the spin-echo (Ramsey) pure-dephasing time in fields up to B=100 G. With direct noise spectroscopy, we further observe a transition from a 1/f to approximately Lorentzian frequency dependence below 10 Hz and a reduction of the noise above 1 MHz with increasing magnetic field. We suggest that these trends are qualitatively consistent with an increase of spin cluster sizes with magnetic field. These results should help to inform a complete microscopic theory of 1/f flux noise in superconducting circuits.

Room-Temperature Strong Coupling of CdSe Nanoplatelets and Plasmonic Hole Arrays.

Exciton polaritons are hybrid light-matter quasiparticles that can serve as coherent light sources. Motivated by applications, room-temperature realization of polaritons requires narrow, excitonic transitions with large transition dipoles. Such transitions must then be strongly coupled to an electromagnetic mode confined in a small volume. While much work has explored polaritons in organic materials, semiconductor nanocrystals present an alternative excitonic system with enhanced photostability and spectral tunability. In particular, quasi-two-dimensional nanocrystals known as nanoplatelets (NPLs) exhibit intense, spectrally narrow excitonic transitions useful for polariton formation. Here, we place CdSe NPLs on silver hole arrays to demonstrate exciton-plasmon polaritons at room temperature. Angle-resolved reflection spectra reveal Rabi splittings up to 149 meV for the polariton states. We observe bright, polarized emission arising from the lowest polariton state. Furthermore, we assess the dependence of the Rabi splitting on the hole-array pitch and the number N of NPLs. While the pitch determines the in-plane momentum for which strong coupling is observed, it does not affect the size of the splitting. The Rabi splitting first increases with NPL film thickness before eventually saturating. Instead of the commonly used [Formula: see text] dependence, we develop an analytical expression that includes the transverse confinement of the plasmon modes to describe the measured Rabi splitting as a function of NPL film thickness.

Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older - United States, 2019.

In October 2018, the Advisory Committee on Immunization Practices (ACIP)* voted to recommend approval of the Recommended Immunization Schedule for Adults, Aged 19 Years or Older, United States, 2019. The 2019 adult immunization schedule, available at https://www.cdc.gov/vaccines/schedules,† summarizes ACIP recommendations in two tables and accompanying notes. The 2019 adult immunization schedule has been approved by the CDC Director, the American College of Physicians, the American Academy of Family Physicians, the American College of Obstetricians and Gynecologists, and the American College of Nurse-Midwives.

Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older - United States, 2018.

In October 2017, the Advisory Committee on Immunization Practices (ACIP) voted to approve the Recommended Immunization Schedule for Adults Aged 19 Years or Older, United States, 2018. The 2018 adult immunization schedule summarizes ACIP recommendations in two figures and a table of contraindications and precautions for vaccines recommended for adults, and is intended is to assist health care providers in implementing the current ACIP recommendations for vaccinating adults. The schedule can be found at https://www.cdc.gov/vaccines/schedules.* The full ACIP recommendations for each vaccine are available at https://www.cdc.gov/vaccines/hcp/acip-recs/index.html. The 2018 adult immunization schedule has also been approved by the American College of Physicians (https://www.acponline.org), the American Academy of Family Physicians (https://www.aafp.org), the American College of Obstetricians and Gynecologists (https://www.acog.org), and the American College of Nurse-Midwives (http://www.midwife.org). The ACIP-recommended use of each vaccine is developed after an in-depth review of vaccine-related data, including data on disease epidemiology, vaccine efficacy and effectiveness, vaccine safety, feasibility of program implementation, and economic aspects of immunization policy (1).

Direct Patterning of Colloidal Quantum-Dot Thin Films for Enhanced and Spectrally Selective Out-Coupling of Emission.

We report on a template-stripping method for the direct surface patterning of colloidal quantum-dot thin films to produce highly luminescent structures with feature sizes less than 100 nm. Through the careful design of high quality bull's-eye gratings we can produce strong directional beaming (10° divergence) with up to 6-fold out-coupling enhancement of spontaneous emission in the surface-normal direction. A transition to narrow single-mode lasing is observed in these same structures at thresholds as low as 120 µJ/cm2. In addition, we demonstrate that these structures can be fabricated on flexible substrates. Finally, making use of the size-tunable character of colloidal quantum dots, we demonstrate spectrally selective out-coupling of light from mixed quantum-dot films. Our results provide a straightforward route toward significantly improved optical properties of colloidal quantum-dot assemblies.

Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older - United States, 2017.

In October 2016, the Advisory Committee on Immunization Practices (ACIP) voted to approve the Recommended Adult Immunization Schedule for Adults Aged 19 Years or Older-United States, 2017. The 2017 adult immunization schedule summarizes ACIP recommendations in two figures, footnotes for the figures, and a table of contraindications and precautions for vaccines recommended for adults. These documents are available at https://www.cdc.gov/vaccines/schedules. The full ACIP recommendations for each vaccine can be found at https://www.cdc.gov/vaccines/hcp/acip-recs/index.html. The 2017 adult immunization schedule was also reviewed and approved by the American College of Physicians (https://www.acponline.org), the American Academy of Family Physicians (https://www.aafp.org), the American College of Obstetricians and Gynecologists (http://www.acog.org), and the American College of Nurse-Midwives (http://www.midwife.org).

Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older--United States, 2016.

In October 2015, the Advisory Committee on Immunization Practices (ACIP)* approved the Recommended Immunization Schedule for Adults Aged 19 Years or Older, United States, 2016. This schedule provides a summary of ACIP recommendations for the use of vaccines routinely recommended for adults aged 19 years or older in two figures, footnotes for each vaccine, and a table that describes primary contraindications and precautions for commonly used vaccines for adults. Although the figures in the adult immunization schedule illustrate recommended vaccinations that begin at age 19 years, the footnotes contain information on vaccines that are recommended for adults that may begin at age younger than age 19 years. The footnotes also contain vaccine dosing, intervals between doses, and other important information and should be read with the figures.

Flexible, High-Speed CdSe Nanocrystal Integrated Circuits.

We report large-area, flexible, high-speed analog and digital colloidal CdSe nanocrystal integrated circuits operating at low voltages. Using photolithography and a newly developed process to fabricate vertical interconnect access holes, we scale down device dimensions, reducing parasitic capacitances and increasing the frequency of circuit operation, and scale up device fabrication over 4 in. flexible substrates. We demonstrate amplifiers with ∼7 kHz bandwidth, ring oscillators with <10 µs stage delays, and NAND and NOR logic gates.

Wedge Waveguides and Resonators for Quantum Plasmonics.

Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light-matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited. We combine state-of-the-art metallic wedges with integrated reflectors and precisely placed colloidal quantum dots (down to the single-emitter level) and demonstrate quantum-plasmonic waveguides and resonators with performance approaching theoretical limits. By exploiting a nearly 10-fold improvement in wedge-plasmon propagation (19 µm at a vacuum wavelength, λvac, of 630 nm), efficient reflectors (93%), and effective coupling (estimated to be >70%) to highly emissive (~90%) quantum dots, we obtain Ag plasmonic resonators at visible wavelengths with quality factors approaching 200 (3.3 nm line widths). As our structures offer modal volumes down to ~0.004λvac(3) in an exposed single-mode waveguide-resonator geometry, they provide advantages over both traditional photonic microcavities and localized-plasmonic resonators for enhancing light-matter interactions. Our results confirm the promise of wedges for creating plasmonic devices and for studying coherent quantum-plasmonic effects such as long-distance plasmon-mediated entanglement and strong plasmon-matter coupling.

Advisory committee on immunization practices recommended immunization schedule for adults aged 19 years or older--United States, 2015.

In October 2014, the Advisory Committee on Immunization Practices (ACIP) approved the Recommended Immunization Schedule for Adults Aged 19 Years or Older, United States, 2015. This schedule provides a summary of ACIP recommendations for the use of vaccines routinely recommended for adults aged 19 years or older in two figures, footnotes for each vaccine, and a table that describes primary contraindications and precautions for commonly used vaccines for adults. Changes in the 2015 adult immunization schedule from the 2014 schedule included the August 2014 recommendation for routine administration of the 13-valent pneumococcal conjugate vaccine (PCV13) in series with the 23-valent pneumococcal polysaccharide vaccine (PPSV23) for all adults aged 65 years or older, the August 2014 revision on contraindications and precautions for the live attenuated influenza vaccine (LAIV), and the October 2014 approval by the Food and Drug Administration to expand the approved age for use of recombinant influenza vaccine (RIV). These revisions were also reviewed and approved by the American College of Physicians, American Academy of Family Physicians, American College of Obstetricians and Gynecologists, and American College of Nurse-Midwives.

Vaccination coverage among adults, excluding influenza vaccination - United States, 2013.

Vaccinations are recommended throughout life to prevent vaccine-preventable diseases and their sequelae. Adult vaccination coverage, however, remains low for most routinely recommended vaccines and below Healthy People 2020 targets. In October 2014, the Advisory Committee on Immunization Practices (ACIP) approved the adult immunization schedule for 2015. With the exception of influenza vaccination, which is recommended for all adults each year, other adult vaccinations are recommended for specific populations based on a person's age, health conditions, behavioral risk factors (e.g., injection drug use), occupation, travel, and other indications. To assess vaccination coverage among adults aged ≥19 years for selected vaccines, CDC analyzed data from the 2013 National Health Interview Survey (NHIS). This report highlights results of that analysis for pneumococcal, tetanus toxoid-containing (tetanus and diphtheria vaccine [Td] or tetanus and diphtheria with acellular pertussis vaccine [Tdap]), hepatitis A, hepatitis B, herpes zoster (shingles), and human papillomavirus (HPV) vaccines by selected characteristics (age, race/ethnicity,† and vaccination indication). Influenza vaccination coverage estimates for the 2013-14 influenza season have been published separately. Compared with 2012, only modest increases occurred in Tdap vaccination among adults aged ≥19 years (a 2.9 percentage point increase to 17.2%), herpes zoster vaccination among adults aged ≥60 years (a 4.1 percentage point increase to 24.2%), and HPV vaccination among males aged 19-26 years (a 3.6 percentage point increase to 5.9%); coverage among adults in the United States for the other vaccines did not improve. Racial/ethnic disparities in coverage persisted for all six vaccines and widened for Tdap and herpes zoster vaccination. Increases in vaccination coverage are needed to reduce the occurrence of vaccine-preventable diseases among adults. Awareness of the need for vaccines for adults is low among the general population, and adult patients largely rely on health care provider recommendations for vaccination. The Community Preventive Services Task Force and the National Vaccine Advisory Committee have recommended that health care providers incorporate vaccination needs assessment, recommendation, and offer of vaccination into every clinical encounter with adult patients to improve vaccination rates and to narrow the widening racial/ethnic disparities in vaccination coverage.

Near-field light design with colloidal quantum dots for photonics and plasmonics.

Colloidal quantum-dots are bright, tunable emitters that are ideal for studying near-field quantum-optical interactions. However, their colloidal nature has hindered their facile and precise placement at desired near-field positions, particularly on the structured substrates prevalent in plasmonics. Here, we use high-resolution electro-hydrodynamic printing (<100 nm feature size) to deposit countable numbers of quantum dots on both flat and structured substrates with a few nanometer precision. We also demonstrate that the autofocusing capability of the printing method enables placement of quantum dots preferentially at plasmonic hot spots. We exploit this control and design diffraction-limited photonic and plasmonic sources with arbitrary wavelength, shape, and intensity. We show that simple far-field illumination can excite these near-field sources and generate fundamental plasmonic wave-patterns (plane and spherical waves). The ability to tailor subdiffraction sources of plasmons with quantum dots provides a complementary technique to traditional scattering approaches, offering new capabilities for nanophotonics.

Postdeployment driving stress and related occupational limitations among veterans of Operation Iraqi Freedom and Operation Enduring Freedom.

Difficulty in driving after deployment has emerged as an impediment for servicemembers returning from Operation Iraqi Freedom and Operation Enduring Freedom (OIF-OEF). This study explored postdeployment driving stress and related occupational limitations using two self-report instruments: the Driver's Stress Profile and the Driving and Occupational Limitations questionnaire. Data gathered from 103 OIF-OEF returnees confirmed that driving and related occupational issues occur postdeployment. Significant low to moderate correlations were found between postdeployment driving stress and limitations in community mobility, leisure, and social participation. The returnees who drove off base more frequently during deployment showed significantly higher levels of postdeployment driving stress than the returnees who drove off base less frequently. Moreover, the returnees who demonstrated higher levels of driving stress and occupational limitations required more time to resume normal driving postdeployment. Findings raise awareness about the need to design effective driver rehabilitation and community reintegration programs for this population.