Phys.org November 8, 2023 The use of single electron spins in quantum dots as qubits requires detailed knowledge about the processes involved in their initialization and operation as well as their relaxation and decoherence. In optical schemes for such spin qubits, spin-flip Raman as well as Auger processes play an important role, in addition to environment-induced spin relaxation. An international team of researchers (Germany, USA – UCLA) demonstrated how to quantitatively access all the spin-related processes in one go by monitoring the charge fluctuations of the quantum dot. They used resonance fluorescence and analyzed the charge fluctuations in terms of […]
Tag Archives: Quantum dots
Arrays of quantum rods could enhance TVs or virtual reality devices
MIT News August 11, 2023 Scalable fabrication of two-dimensional (2D) arrays of quantum dots (QDs) and quantum rods (QRs) with nanoscale precision is required for numerous device applications. However, self-assembly–based fabrication of such arrays using DNA origami typically suffers from low yield due to inefficient QD and QR DNA functionalization and it is challenging to organize solution-assembled DNA origami arrays on 2D device substrates while maintaining their structural fidelity. Researchers at MIT reduced manufacturing time from a few days to a few minutes by preparing high-density DNA-conjugated QDs/QRs from organic solution using a dehydration and rehydration process. They used a […]
Using nanofaceting to manipulate quantum dots into nanocrystals
Phys.org May 17, 2023 Colloidal nanocrystals (NCs) have shown remarkable promise for optoelectronics, energy harvesting, photonics, and biomedical imaging. In addition to optimizing quantum confinement, the current challenge is to obtain a better understanding of the critical processing steps and their influence on the evolution of structural motifs. Through computational simulations and electron microscopy an international team of researchers (UK, France, South Korea, China) has shown that nanofaceting can occur during nanocrystal synthesis from a Pb-poor environment in a polar solvent. This could explain the curved interfaces and the olivelike-shaped NCs observed experimentally when these conditions were employed. Furthermore, the […]
High-visibility quantum interference between two independent semiconductor quantum dots achieved
Phys.org December 28, 2022 There has been exciting recent progress in satellite-based quantum communications and quantum repeaters, but a lack of suitable single-photon sources has hampered further advances. The visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%, and the distances were limited from a few meters to kilometers. An international team of researchers (China, Germany) has shown quantum interference between two single photons from independent QDs separated by a 302 km optical fiber. The single photons were generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions were used to […]
Chemists create quantum dots at room temperature using lab-designed protein
Phys.org December 12, 2022 Researchers at Princeton University used a lab-designed protein (ConK) which facilitated the formation of cadmium sulfide quantum dots by catalyzing the production of a reactive sulfur species from the amino acid cysteine. ConK catalyzed the desulfurization of cysteine to H2S, which was used to synthesize CdS nanocrystals in solution. The quantum dots had optical properties like those seen in chemically synthesized quantum dots. CdS nanocrystals synthesized using ConK have slower growth rates and a different growth mechanism than those synthesized using natural biomineralization pathways and have two desirable properties not observed during biomineralization using natural proteins […]
Engineers develop a low-cost, quantum-dot-enhanced terahertz camera
Nanowerk November 5, 2022 The currently available THz detectors are limited in many aspects of their performance, including sensitivity, speed, bandwidth, and operating temperature. Most do not allow the characterization of THz polarization states. The recent observation of THz-driven luminescence in quantum dots offers a possible detection mechanism via field-driven interdot charge transfer. An international team of researchers (USA – MIT, University of Minnesota, , Stanford University, SLAC National Accelerator Laboratory, South Korea) has demonstrated a room-temperature CMOS THz camera and polarimeter based on quantum-dot-enhanced THz-to-visible upconversion mechanism with optimized luminophore geometries and fabrication designs. Besides broadband and fast responses, […]
Ultrafast imaging of terahertz electric waveforms using quantum dots
Phys.org January 4, 2022 Only few imaging schemes can resolve sub-wavelength fields in the THz range, such as scanning-probe techniques, electro-optic sampling, and ultrafast electron microscopy. The intrinsic constraints on sample geometry, acquisition speed and field strength limit their applicability. An international team of researchers (Germany, Australia) harnessed the quantum-confined Stark-effect to encode ultrafast electric near-fields into colloidal quantum dot luminescence. Their approach, termed Quantum-probe Field Microscopy (QFIM), combines far-field imaging of visible photons with phase-resolved sampling of electric waveforms. By capturing ultrafast movies, they spatio-temporally resolved a Terahertz resonance inside a bowtie antenna and unveiled the propagation of a […]
Ultrathin quantum dot LED that can be folded freely as paper
Science Daily September 27, 2021 Researchers in South Korea have demonstrated that 3D foldable quantum dot light-emitting diodes (QLEDs) can be created using laser patterning and metal etch-stop layers with customized ablation thresholds. The approach allows etching to be limited to selected layers of the multilayered QLEDs, and it can be precisely tuned by using alloy-type etch-stop layers. The approach can be used to create QLED architectures with extremely small bending radii (0.047 mm). They have illustrated its capabilities by fabricating a 3D foldable passive matrix array of QLEDs that can display letters and numbers. The entire QLED including the crease […]
‘Connecting the dots’ for quantum networks
Science Daily July 9, 2019 For quantum dots to “communicate”, they must emit light at the same wavelength. The size of a quantum dot determines this emission wavelength. Instead of making quantum dots perfectly identical to begin with, researchers at the US Naval Research Laboratory change their wavelength afterwards by shrink-wrapping them with laser-crystallized hafnium oxide, squeezing the quantum dots, which shifts their wavelength in a very controllable way. Doing this for many quantum dots in an integrated circuit, could be used for optical, rather than electrical computing. The technique could accelerate the development of quantum information technologies and brain-inspired […]
Engineers develop novel strategy for designing tiny semiconductor particles for wide-ranging applications
Science Daily January 25, 2019 An international team of researchers (Singapore, China) has developed a cheaper and more scalable bottom-up synthesis strategy that can consistently construct TMD QDs (transition metal dichalcogenide quantum dots) of a specific size and properties. To demonstrate the proof-of-concept they synthesised MoS2 QDs with specific properties for biomedical applications. They have successfully synthesised a small library of seven TMD QDs and were able to alter their electronic and optical properties accordingly. They process can be used to optimize TMD QDs for applications such as the next generation TV and electronic device screens, advanced electronics components and […]