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Researchers from the Moscow Institute of Physics and Technology, joined by a colleague from Argonne National Laboratory, U.S., have implemented an advanced quantum algorithm for measuring physical quantities using simple optical tools. Published in Scientific Reports, their study takes us a step closer to affordable linear optics-based sensors with high performance characteristics. Such tools are sought after in diverse research fields, from astronomy to biology.

Maximizing the sensitivity of measurement tools is crucial for any field of science and technology. Astronomers seek to detect remote cosmic phenomena, biologists need to discern exceedingly tiny organic structures, and engineers have to measure the positions and velocities of objects, to name a few examples.

Until recently, no measurement tool could ensure precision above the so-called shot noise limit, which has to do with the statistical features inherent in classical observations. Quantum technology has provided a way around this, boosting precision to the fundamental Heisenberg limit, stemming from the basic principles of quantum mechanics. The LIGO experiment, which detected gravitational waves for the first time in 2016, shows it is possible to achieve Heisenberg-limited sensitivity by combining complex optical interference schemes and quantum techniques.

In the consumer electronics industry, quantum dots are used to dramatically improve color reproduction in TV displays. That’s because LCD TV displays, the kind in most of our living rooms, require a backlight. This light is typically made up of white, or white-ish LEDs. The LCD filters the white light into red, green, and blue pixels; their combinations create the colors that appear on the screen.

Before quantum dots, filtering meant that much of the light didn’t make it to the screen. Putting a layer of quantum dots between the LEDs and the LCD, however, changes that equation. QD TVs use blue LEDs as the light source, then take advantage of the quantum effect to shift some of that light to tightly constrained red and green wavelengths. Because only this purified light reaches the filters—instead of the full spectrum that makes up white light—far less is blocked and wasted.

It turns out that this same approach to making your TV picture better can make plants grow faster, because plants, like LCD filters, are tuned to certain colors of light.

It’s always exciting when you can bridge two different physical concepts that seem to have nothing in common—and it’s even more thrilling when the results have as broad a range of possible fields of application as from fault-tolerant quantum computation to quantum gravity.

Physicists love to draw connections between distinct ideas, interconnecting concepts and theories to uncover new structure in the landscape of scientific knowledge. Put together information theory with quantum mechanics and you’ve opened a whole new field of quantum information theory. More recently, machine learning tools have been combined with many-body physics to find new ways to identify phases of matter, and ideas from quantum computing were applied to Pozner molecules to obtain new plausible models of how the brain might work.

Continue reading “Symmetries and quantum error correction” »

According to new research by SISSA, ICTP and INFN, black holes could be like holograms, in which all the information to produce a three-dimensional image is encoded in a two-dimensional surface. As affirmed by quantum theories, black holes could be incredibly complex, and concentrate an enormous amount of information in two dimensions, like the largest hard disks that exist in nature. This idea aligns with Einstein’s theory of relativity, which describes black holes as three dimensional, simple, spherical and smooth, as depicted in the first-ever image of a black hole that circulated in 2019. In short, black holes appear to be three dimensional, just like holograms. The study, which unites two discordant theories, has recently been published in Physical Review X.

The mystery of black holes

For scientists, black holes pose formidable theoretical challenges for many reasons. They are, for example, excellent representatives of the great difficulties of theoretical physics in uniting the principles of Einstein’s general theory of relativity with those of the quantum physics of gravity. According to the relativity, black holes are simple bodies without information. According to quantum physics, as claimed by Jacob Bekenstein and Stephen Hawking, they are the most complex existing systems because they are characterized by enormous entropy, which measures the complexity of a system, and consequently contain a lot of information.

Technion Professor Ido Kaminer and his team have made a dramatic breakthrough in the field of quantum science: a quantum microscope that records the flow of light, enabling the direct observation of light trapped inside a photonic crystal.

Their research, “Coherent Interaction Between Free Electrons and a Photonic Cavity,” was published in Nature. All the experiments were performed using a unique ultrafast transmission electron microscope at the Technion-Israel Institute of Technology. The microscope is the latest and most versatile of a handful that exist in the scientific world.

Continue reading “One-of-a-kind microscope enables breakthrough in quantum science” »

A visualization of the electronic structure of semiconductors made with 2D materials may pave the way for quantum computers and better mobile devices.

Learning quantum error correction: the image visualizes the activity of artificial neurons in the Erlangen researchers’ neural network while it is solving its task. © Max Planck Institute for the Science of Light.

Neural networks enable learning of error correction strategies for computers based on quantum physics

Quantum computers could solve complex tasks that are beyond the capabilities of conventional computers. However, the quantum states are extremely sensitive to constant interference from their environment. The plan is to combat this using active protection based on quantum error correction. Florian Marquardt, Director at the Max Planck Institute for the Science of Light, and his team have now presented a quantum error correction system that is capable of learning thanks to artificial intelligence.

A team of researchers at California Institute of Technology has found that arrays of strontium Rydberg atoms show promise for use in a quantum computer. In their paper published in the journal Nature Physics, the researchers describe their study of quantum entangled alkaline-earth Rydberg atoms arranged in arrays and what they learned about them. In the same issue, Wenhui Li, with the National University of Singapore, has published a News & Views piece exploring the state of quantum computing research, and outlines the work done by the team at CIT.

Quantum computers capable of conducting real computing work have still not been realized, but work continues as scientists are confident that the goal will be reached. And as Li notes, most of the early-stage demo quantum computers are based on superconducting qubits or trapped ion platforms, though other systems are being studied, as well. One such system is based on neutral atoms in which the charges of the protons and electrons balance. In this new effort, the researchers looked at a type of neutral atom system based on Rydberg atoms (excited atoms with one or more electrons that also have a high quantum number). To use such atoms in a quantum computer, they must, of course, be entangled—and there needs to be a lot of them, generally arranged in an array.

In their work, the team at CIT developed a way to demonstrate entanglement of Rydberg atoms in arrays—and as part of the system, they were able to detect and control Rydberg qubits with unprecedented fidelities. To achieve this feat, they began with realizing photon coupling between different levels of Rydberg ground-state qubits, thus avoiding scattering. Doing so also allowed for efficient detection of Rydberg states, greatly improving detection fidelity. The researchers also demonstrated two-qubit entanglement using tweezer potentials, also with high fidelity.

Unprecedented View

The researchers believe this new nanoscale imaging technique could lead to the development of new materials and drugs, as well as the creation of better quantum computing systems.

“We can now see something that we couldn’t see before,” researcher Christopher Lutz told The New York Times. “So our imagination can go to a whole bunch of new ideas that we can test out with this technology.”