The aim of this review is to provide quantum engineers with an introductory guide to the central concepts and challenges in the rapidly accelerating field of superconducting quantum circuits. Over the past twenty years, the field has matured from a predominantly basic research endeavor to one that increasingly explores the engineering of larger-scale superconducting quantum systems. Here, we review several foundational elements -qubit design, noise properties, qubit control, and readout techniques -developed during this period, bridging fundamental concepts in circuit quantum electrodynamics (cQED) and contemporary, stateof-the-art applications in gate-model quantum computation.
Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.
The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). Here, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad-frequency tunability, strong anharmonicity, high reproducibility and relaxation times in excess of 40 μs at its flux-insensitive point. Qubit relaxation times T1 across 22 qubits are consistently matched with a single model involving resonator loss, ohmic charge noise and 1/f-flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal-photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2≈85 μs, approximately the 2T1 limit. In addition to realizing an improved flux qubit, our results uniquely identify photon shot noise as limiting T2 in contemporary qubits based on transverse qubit–resonator interaction.
Lead-halide perovskites have transcended photovoltaics. Perovskite light-emitting diodes (PeLEDs) emerge as a new field to leverage on these fascinating semiconductors. Here, we report the first use of completely inorganic CsPbBr3 thin films for enhanced light emission through controlled modulation of the trap density by varying the CsBr-PbBr2 precursor concentration. Although pure CsPbBr3 films can be deposited from equimolar CsBr-PbBr2 and CsBr-rich solutions, strikingly narrow emission line (17 nm), accompanied by elongated radiative lifetimes (3.9 ns) and increased photoluminescence quantum yield (16%), was achieved with the latter. This is translated into the enhanced performance of the resulting PeLED devices, with lower turn-on voltage (3 V), narrow electroluminescence spectra (18 nm) and higher electroluminescence intensity (407 Cd/m(2)) achieved from the CsBr-rich solutions.
Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, affecting their physical and chemical evolution. Studies of atmospheric escape from
Giant exoplanets orbiting close to their host stars have high temperatures because of the immense stellar irradiation which they receive. The extreme energy input leads to the expansion of the atmosphere and the escape of neutral hydrogen 1 2 3 . A particularly intriguing case among the hot giant planets is KELT-9b -an exoplanet orbiting very close to an early A-type star with the highest temperature (∼ 4600 K at day-side) among all the exoplanets known so far 4 . The atmospheric composition and dynamic of such a unique planet have been unknown. Here we report the first detection of an extended hot hydrogen atmosphere around KELT-9b. The detection was achieved by measuring the atomic hydrogen absorption during transit with the Balmer H α line, which is unusually strong mainly due to the high level of extreme-ultraviolet radiation from the star. We detected a significant wavelength shift of the H α absorption which is mostly attributed to the planetary orbital motion 5 . The obtained transmission spectrum has a significant line contrast (1.15% extra absorption at the H α line centre). The observation implies that the effective radius at the H α line centre is ∼ 1.64 times the size of the planetary radius, indicating the planet has a largely extended hydrogen envelope close to the size of the Roche lobe ( 1.91 +0.22 −0.26 R planet ) and is probably undergoing dramatic atmosphere escape.We observed two transits of KELT-9b on August 6 and September 21, 2017 with the CARMENES instrument 6 . CARMENES is a high-resolution (R ∼ 94 600 in the visual channel) spectrograph installed at the 3.5 m telescope of the Calar Alto Observatory. Each of the observations lasted for ∼ 6 hours covering the 4 hours transit and 1 hour before and after transit.For each transit dataset, we firstly removed the telluric H 2 O lines at the H α wavelength range and then aligned all the spectra to the stellar rest frame. A reference spectrum was obtained by combining all the spectra observed during out-of-transit. This reference spectrum is regarded as the spectrum of the star and each observed spectrum was then divided by the reference spectrum to remove the stellar H α spectrum. In this way, we obtained planetary absorption spectra with telluric and stellar lines removed. We then binned the planetary absorption spectra from both nights with a 0.01 orbital phase step, i. e. the spectra within each 0.01 phase bin were averaged with the spectral 1 arXiv:1807.00869v1 [astro-ph.EP] 2 Jul 2018 signal-to-noise ratio (SNR) as weight.The obtained planetary absorption spectra are displayed in Fig.1a. The figure shows a black shadow during transit which is the result of the H α absorption. The absorption feature has a significant wavelength shift and this radial velocity (RV) change is mostly attributed to the planetary orbital motion. We modeled the planetary absorption feature assuming it has a Gaussian profile. The semi-amplitude of the planetary orbital motion(K planet ) was set as a free parameter in the model. We included an atmosphere wind speed (...
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