Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: quantum physics – Page 731

Scientists uncover a process that stands in the way of making quantum dots brighter

Bright semiconductor nanocrystals known as quantum dots give QLED TV screens their vibrant colors. But attempts to increase the intensity of that light generate heat instead, reducing the dots’ light-producing efficiency.

A new study explains why, and the results have broad implications for developing future quantum and photonics technologies where replaces electrons in computers and fluids in refrigerators, for example.

In a QLED TV screen, dots absorb blue light and turn it into green or red. At the low energies where TV screens operate, this conversion of light from one color to another is virtually 100% efficient. But at the higher excitation energies required for brighter screens and other technologies, the efficiency drops off sharply. Researchers had theories about why this happens, but no one had ever observed it at the atomic scale until now.

Crucial Milestone for Scalable Quantum Technology: 2D Array of Semiconductor Qubits That Functions as a Quantum Processor

The heart of any computer, its central processing unit, is built using semiconductor technology, which is capable of putting billions of transistors onto a single chip. Now, researchers from the group of Menno Veldhorst at QuTech, a collaboration between TU Delft and TNO, have shown that this technology can be used to build a two-dimensional array of qubits to function as a quantum processor. Their work, a crucial milestone for scalable quantum technology, was published today (March 242021) in Nature.

Quantum computers have the potential to solve problems that are impossible to address with classical computers. Whereas current quantum devices hold tens of qubits — the basic building block of quantum technology — a future universal quantum computer capable of running any quantum algorithm will likely consist of millions to billions of qubits. Quantum dot qubits hold the promise to be a scalable approach as they can be defined using standard semiconductor manufacturing techniques. Veldhorst: “By putting four such qubits in a two-by-two grid, demonstrating universal control over all qubits, and operating a quantum circuit that entangles all qubits, we have made an important step forward in realizing a scalable approach for quantum computation.”

Novel thermometer can accelerate quantum computer development

Researchers at Chalmers University of Technology, Gothenburg, Sweden, have developed a novel type of thermometer that can simply and quickly measure temperatures during quantum calculations with extremely high accuracy. The breakthrough provides a benchmarking tool for quantum computing of great value—and opens up for experiments in the exciting field of quantum thermodynamics.

Key components in quantum computers are coaxial cables and waveguides—structures that guide waveforms and act as the vital connection between the and the classical electronics that control it. Microwave pulses travel along the waveguides to the quantum processor, and are cooled down to extremely along the way. The also attenuates and filters the pulses, enabling the extremely sensitive quantum computer to work with stable quantum states.

In order to maximize control over this mechanism, the researchers need to be sure that these waveguides are not carrying noise due to thermal motion of electrons on top of the pulses that they send. In other words, they have to measure the temperature of the electromagnetic fields at the cold end of the microwave waveguides, the point where the controlling pulses are delivered to the computer’s qubits. Working at the lowest possible temperature minimizes the risk of introducing errors in the qubits.

Action potentials induce biomagnetic fields in carnivorous Venus flytrap plants

“Previously reported detection of plant biomagnetism, which established the existence of measurable magnetic activity in the plant kingdom, was carried out using superconducting-quantum-interference-device (SQUID) magnetometers1, 5, 16. Atomic magnetometers are arguably more attractive for biological applications, since, unlike SQUIDs34, 35, they are non-cryogenic and can be miniaturized to optimize spatial resolution of measured biological features14, 15, 36. In the future, the SNR of magnetic measurements in plants will benefit from optimizing the low-frequency stability and sensitivity of atomic magnetometers. Just as noninvasive magnetic techniques have become essential tools for medical diagnostics of the human brain and body, this noninvasive technique could also be useful in the future for crop-plant diagnostics—by measuring the electromagnetic response of plants facing such challenges as sudden temperature change, herbivore attack, and chemical exposure.”

Upon stimulation, plants elicit electrical signals that can travel within a cellular network analogous to the animal nervous system. It is well-known that in the human brain, voltage changes in certain regions result from concerted electrical activity which, in the form of action potentials (APs), travels within nerve-cell arrays. Electro-and magnetophysiological techniques like electroencephalography, magnetoencephalography, and magnetic resonance imaging are used to record this activity and to diagnose disorders. Here we demonstrate that APs in a multicellular plant system produce measurable magnetic fields. Using atomic optically pumped magnetometers, biomagnetism associated with electrical activity in the carnivorous Venus flytrap, Dionaea muscipula, was recorded. Action potentials were induced by heat stimulation and detected both electrically and magnetically.

Pioneering Experiment Turns IBM’s Largest Quantum Computer Into a Quantum Material

Pioneering experiment could help design energy-efficient materials.

In a groundbreaking study published in Physical Review Research, a group of University of Chicago scientists announced they were able to turn IBM’s largest quantum computer into a quantum material itself.

They programmed the computer such that it turned into a type of quantum material called an exciton condensate, which has only recently been shown to exist. Such condensates have been identified for their potential in future technology, because they can conduct energy with almost zero loss.

The Emerging Paths Of Quantum Computing

By Chuck Brooks

The world of computing has witnessed seismic advancements since the invention of the electronic calculator in the 1960s. The past few years in information processing have been especially transformational. What were once thought of as science fiction fantasies are now technological realties. Classical computing has become more exponentially faster and more capable and our enabling devices smaller and more adaptable.

Chromatic light particle effect revealed for the development of photonic quantum networks

It’s another step on the road to developing quantum information processing applications: A key experiment succeeded in going beyond the previously defined limits for photon applications. Anahita Khodadad Kashi and Prof. Dr. Michael Kues from the Institute of Photonics and the Cluster of Excellence PhoenixD at Leibniz University Hannover (Germany) have demonstrated a novel interference effect. The scientists have thus shown that new color-coded photonic networks can be tapped, and the number of photons involved can be scaled. “This discovery could enable new benchmarks in quantum communication, computational operations of quantum computers as well as quantum measurement techniques and is feasible with existing optical telecommunication infrastructure,” says Kues.

The decisive experiment was successfully performed in the newly established Quantum Photonics Laboratory (QPL) of the Institute of Photonics and the Hannover Centre for Optical Technologies at Leibniz University Hannover. Anahita Khodadad Kashi succeeded in quantum-mechanically interfering independently generated pure photons with different colors, i.e., frequencies. Khodadad Kashi detected a so-called Hong-Ou-Mandel effect.

Hong-Ou-Mandel interference is a fundamental effect of quantum optics that forms the basis for many processing applications—from quantum computing to quantum metrology. The effect describes how two photons behave when they collide on a spatial beam splitter and explains the phenomenon of quantum mechanical interference.

Solving ‘barren plateaus’ is the key to quantum machine learning

Many machine learning algorithms on quantum computers suffer from the dreaded “barren plateau” of unsolvability, where they run into dead ends on optimization problems. This challenge had been relatively unstudied—until now. Rigorous theoretical work has established theorems that guarantee whether a given machine learning algorithm will work as it scales up on larger computers.

“The work solves a key problem of useability for . We rigorously proved the conditions under which certain architectures of variational quantum algorithms will or will not have barren plateaus as they are scaled up,” said Marco Cerezo, lead author on the paper published in Nature Communications today by a Los Alamos National Laboratory team. Cerezo is a post doc researching at Los Alamos. “With our theorems, you can guarantee that the architecture will be scalable to quantum computers with a large number of qubits.”

“Usually the approach has been to run an optimization and see if it works, and that was leading to fatigue among researchers in the field,” said Patrick Coles, a coauthor of the study. Establishing mathematical theorems and deriving first principles takes the guesswork out of developing algorithms.

/* */