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Quantum technologies are extremely sensitive to environmental disturbance. Control techniques inspired by classical systems engineering allow selective filtering of the noise spectrum, suppressing time-varying noise over defined frequency bands.Letter p825; News & Views p794 IMAGE: HARRISON BALL AND MICHAEL J. BIERCUK COVER DESIGN: ALLEN BEATTIE
Many people around the world will remember 2014 as the year Brazil hosted the football World Cup. But for Brazil's science communities, the decisions made by the new government could leave scars much deeper than the semi-final defeat.
The 2014 Nobel Prize in Physics has been awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources."
Astrophysical observations of Hawking radiation may be out of reach, but evidence for the self-amplification of Hawking radiation has now been observed in a sonic analogue of a black hole.
Rapidly changing noise impedes high-fidelity quantum control. An engineering framework for predicting and mitigating such dynamics has now been validated, revealing physical insights into the time evolution of quantum states.
A microcavity device operating in the strong light–matter interaction regime can produce coherent perfect absorption of photons — providing a viable system for the perfect feeding of polaritons.
The ability to harness spin polarization is critical for many semiconductor spin devices. It now seems that spin–orbit coupling with locally broken symmetry can enable a giant spin polarization in a semiconductor that is otherwise inversion symmetric.
Plasmons offer the tantalizing prospect of accelerated light–matter interactions. Accelerated dynamics has now been observed in a hybrid plasmonic laser or spaser, capable of producing pulses on ultrafast timescales.
Laser control of atomic ions through dipole-forbidden transitions has provided a way of probing quantum mechanics. These transitions have now been observed in molecular ions, opening the door to a new generation of spectroscopy experiments.
Exciton–polaritons, resulting from the light–matter coupling between an exciton and a photon in a cavity, form Bose–Einstein-like condensates above a critical density. Various aspects of the physics of exciton–polariton condensates are now reviewed.
The electrons associated with the conducting surface states of topological insulators are described by a two-component wavefunction. Experiments on Bi2Se3 now show that the structure of Landau levels reflects this two-component nature.
Dipole-forbidden vibrational transitions in molecular ions are very weak and difficult to characterize. The sympathetic cooling provided by a Coulomb crystal is shown to allow interrogation times long enough to observe them.
Quantum technologies are extremely sensitive to environmental disturbance. Control techniques inspired by classical systems engineering allow selective filtering of the noise spectrum, suppressing time-varying noise over defined frequency bands.
The absorption properties of a resonator can be tuned by varying the phase between incoming coherent light beams. Such control is now shown under strong coupling conditions, allowing all incoming energy to be converted into polaritons.
The coupling between spin, valley and layer degrees of freedom in transition-metal dichalcogenides is shown to give rise to spin-polarized electron states, providing opportunities to create and manipulate spin and valley polarizations in bulk solids.
Nuclear magnetic resonance measurements reveal two separate relaxation channels—one associated with a Fermi liquid state and the other with a non-Fermi liquid state—coexisting near a quantum phase transition in YbRh2Si2.
The pairing symmetry of iron pnictide superconductors has been hotly debated. First-principles simulations suggest low-energy spin excitations play a central role in raising the superconducting transition temperature of such materials.
Randomness can disorder a two-dimensional vortex lattice and lead to enhanced long-range correlations. The resulting order–disorder transition occurs in two steps, with critical exponents exceeding predictions.
Spin relaxation in graphene is much faster than theoretically expected. Now, a scenario based on a mixing of spin and pseudospin degrees of freedom and defect-induced spatial spin–orbit coupling variations predicts longer spin relaxation times.
Quantum effects allow black holes to radiate—offering a glimpse of how quantum field theory and general relativity might fit together. Hawking radiation has now been observed in a black hole analogue, with evidence that it can self-amplify.
Electron scattering limits the optical excitations produced by metal-based lasers to femtosecond timescales. But sub-picosecond pulsing can be achieved in a plasmonic nanowire laser by operating near the surface plasmon frequency.
A superconductor placed near a quantum Hall edge can show emergent excitations with a range of exotic features. For instance, such heterostructures are predicted to exhibit non-local signatures that are direct extensions of ‘Andreev reflection’.
Cuprate superconductors are created by adding electrons or holes to a ‘parent’ compound. They have dissimilar phase diagrams and the asymmetry is further highlighted by unexpected collective modes measured using resonant inelastic X-ray scattering.