Lifeboat Foundation

Despite the young age of the research field, substantial progress has been made in the study of metal halide perovskite nanocrystals (HPNCs). Just as their thin-film counterparts are used for light absorption in solar cells, they are on the way to revolutionizing research on novel chromophores for light emission applications. Exciting physics arising from their peculiar structural, electronic, and excitonic properties are being discovered with breathtaking speed. Many things we have learned from the study of conventional semiconductor quantum dots (CSQDs) of II–VI (e.g., CdSe), IV–VI (e.g., PbS), and III–V (e.g., InP) compounds have to be thought over, as HPNCs behave differently. This Feature Article compares both families of nanocrystals and then focuses on approaches for substituting toxic heavy metals without sacrificing the unique optical properties as well as on surface coating strategies for enhancing the long-term stability.

• • Top of Page
  • Abstract
  • Introduction
  • Optical Properties of CSQDs and HPNCs
  • Specificities of Cd- and Pb-Containing NCs Favoring Outstanding Optoelectronic Properties
  • General Strategies for Replacing Toxic Heavy Metals in Nanocrystals
  • Conclusions and Perspectives
  • References

In the early 1980s the quest for novel photocatalysts, fueled by the oil crisis in the preceding decade, led to the discovery of semiconductor quantum dots. Pioneering works by Efros, Brus, and Henglein showed both experimentally and theoretically that the reduction of size of semiconductor particles (e.g., CdS) down to the nanometer range induces a significant change in their band gap energy.(1−3) The underlying quantum confinement effect, occurring when the nanocrystal size is (significantly) smaller than twice the exciton Bohr radius of the semiconductor material (Table 1), leads to an increase, scaling with 1/r, of the band gap energy. It also gives rise to the appearance of discrete energy levels at the place of continuous valence and conduction energy bands. In the same period Ekimov as well as Itoh and co-workers observed quantum confinement in small CuCl crystallites embedded in a glass or a NaCl matrix.

Love: The Glue That Holds the Universe Together. “Love contrasts with fear, light with dark, black implies white, self implies other, suffering implies ecstasy, death implies life. We can devise and apprehend something only in terms of what it is not. This is the cosmic binary code: Ying/Yang, True/False, Infinite/Finite, Masculine/Feminine, On/Off, Yes/No… There are really only two opposing forces at play: love as universal integrating force and fear as universal disintegrating force… Like in Conway’s Game of Life information flows along the path of the least resistance influenced by the bigger motivator – either love factor of fear factor (or, rather, their sophisticated gradients like pleasure and pain) – Go or No go. Love and its contrasting opposite fear is what makes us feel alive… Love is recognized self-similarity in the other, a fractal algorithm of the least resistance. And love, as the finest intelligence, is obviously an extreme form of collaboration… collectively ascending to higher love, “becoming one planet of love.” Love is the glue that holds the Universe together…” –Excerpt from ‘The Syntellect Hypothesis: Five Paradigms of the Mind’s Evolution’ by Alex Vikoulov, available now on Amazon.

#SyntellectHypothesis #AlexVikoulov #Love

P.S. Extra For Digitalists: “In this quantum [computational] multiverse the essence of digital IS quantum entanglement. The totality of your digital reality is what your conscious mind implicitly or explicitly chooses to experience out of the infinite -\-\ a cocktail of love response and fear response.”

Absence of light exerts a weird cooling effect.

Canada is investing $2.7 million to develop quantum radar technology.

Electronics rely on the movement of negatively-charged electrons. Physicists strive to understand the forces that push these particles into motion, with the goal of harnessing their power in new technologies. Quantum computers, for instance, employ a fleet of precisely controlled electrons to take on goliath computational tasks. Recently, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) demonstrated how microwaves cut in on the movements of electrons. The findings may contribute to future quantum computing technology.

The logic operations of normal computers are based on zeros and ones, and this binary code limits the volume and type of information the machines can process. Subatomic particles can exist in more than two discrete states, so quantum computers harness electrons to crunch complex data and perform functions at whiplash speed. To keep electrons in limbo for experiments, scientists capture the particles and expose them to forces that alter their behavior.

In the new study, published December 18, 2018 in Physical Review B, OIST researchers trapped electrons in a frigid, vacuum-sealed chamber and subjected them to microwaves. The particles and light altered each other’s movement and exchanged energy, which suggests the sealed system could potentially be used to store quantum information – a microchip of the future.

Possible quantum computing at room temperature. Scientists working with hexagonal boron nitride, which allows them to work in two-dimensional arrays. Simpler than using 3D objects such as diamonds.

Researchers have now demonstrated a new hardware platform based on isolated electron spins in a two-dimensional material. The electrons are trapped by defects in sheets of hexagonal boron nitride, a one-atom-thick semiconductor material, and the researchers were able to optically detect the system’s quantum states.

Quantum physics sets the laws that dominate the universe at a small scale. The ability to harness quantum phenomena could lead to machines like quantum computers, which are predicted to perform certain calculations much faster than conventional computers. One major problem with building quantum processors is that the tracking and controlling quantum systems in real time is a difficult task because quantum systems are overwhelmingly fragile: Manipulating these systems carelessly introduces significant errors in the final result. New work by a team at Aalto could lead to precise quantum computers.

The researchers report controlling quantum phenomena in a custom-designed electrical circuit called a transmon. Chilling a transmon chip to within a few thousandths of a degree above absolute zero induces a quantum state, and the chip starts to behave like an artificial atom. One of the quantum features that interests researchers is that the energy of the transmon can only take specific values, called energy levels. The energy levels are like steps on a ladder: A person climbing the ladder must occupy a step, and can’t hover somewhere between two steps. Likewise, the transmon energy can only occupy the set values of the energy levels. Shining microwaves on the circuit induces the transmon to absorb the energy and climb up the rungs of the ladder.

In work published 8 February in the journal Science Advances, the group from Aalto University led by Docent Sorin Paraoanu, senior university lecturer in the Department of Applied Physics, has made the transmon jump more than one energy level in a single go. Previously, this has been possible only by very gentle and slow adjustments of the microwave signals that control the device. In the new work, an additional microwave control signal shaped in a very specific way allows a fast, precise change of the energy level. Dr. Antti Vepsäläinen, the lead author, says, “We have a saying in Finland: ‘hiljaa hyvää tulee’ (slowly does it). But we managed to show that by continuously correcting the state of the system, we can drive this process more rapidly and at high fidelity.”

Princeton researchers have demonstrated a new way of making controllable “quantum wires” in the presence of a magnetic field, according to a new study published in Nature.

The researchers detected channels of conducting electrons that form between two quantum states on the surface of a bismuth crystal subjected to a high magnetic field. These two states consist of electrons moving in elliptical orbits with different orientations.

To the team’s surprise, they found that the current flow in these channels can be turned on and off, making these channels a new type of controllable quantum wire.

The quantum internet will require fast-moving data and the Australian National University believes it has found a way to measure information stored in light particles which will pave the way for a safe “data superhighway”.