Demonstration with erbium marks a step towards long-distance quantum communication.
Category: quantum physics – Page 249
Using laser light, researchers have developed the most robust method currently known to control individual qubits made of the chemical element barium. The ability to reliably control a qubit is an important achievement for realizing future functional quantum computers.
The paper, “A guided light system for agile individual addressing of Ba+ qubits with 10−4 level intensity crosstalk,” was published in Quantum Science and Technology.
This new method, developed at the University of Waterloo’s Institute for Quantum Computing (IQC), uses a small glass waveguide to separate laser beams and focus them four microns apart, about four-hundredths of the width of a single human hair. The precision and extent to which each focused laser beam on its target qubit can be controlled in parallel is unmatched by previous research.
Researchers at Max Planck Institute of Quantum Optics (MPQ) and Technical University of Munich (TUM) demonstrated a potential platform for large-scale quantum computing and communication networks. Secure quantum networks are of interest to financial institutions, medical facilities, government agencies, and other organizations that handle personal data and classified information due to their much higher level of security.
To create an environment that supported quantum computing, the researchers excited individual atoms of the rare-earth metal erbium. The excitation process caused the erbium atoms to emit single photons with properties suitable for the construction of quantum networks.
Quantum computing has the potential to revolutionize the world, allowing massive health and science computation problems to be solved exponentially faster than by classic computing. But quantum computers have a big drawback—they can only operate in subzero temperatures.
“In order to make quantum computers work, we cannot use them at room temperature,” said Ahmed El-Gendy, Ph.D., an associate professor of physics at The University of Texas at El Paso. “That means we will need to cool the computers and cool all the materials, which is very expensive.”
Now, physicists at The University of Texas at El Paso believe they have made a quantum leap in that regard. Led by El-Gendy, the team has developed a highly magnetic quantum computing material—100 times more magnetic than pure iron—that functions at regular temperature. The material is described in a summer issue of the journal Applied Physics Letters.
Researchers at the University of Stuttgart have demonstrated that a key ingredient for many quantum computation and communication schemes can be performed with an efficiency that exceeds the commonly assumed upper theoretical limit—thereby opening up new perspectives for a wide range of photonic quantum technologies.
Quantum science has not only revolutionized our understanding of nature—it is also inspiring groundbreaking new computing, communication and sensor devices. Exploiting quantum effects in such “quantum technologies” typically requires a combination of deep insight into the underlying quantum-physical principles, systematic methodological advances, and clever engineering.
And it is precisely this combination that researches in the group of Prof. Stefanie Barz at the University of Stuttgart and the Center for Integrated Quantum Science and Technology (IQST) have delivered in a recent study, in which they have improved the efficiency of an essential building block of many quantum devices beyond a seemingly inherent limit. The work is published in the journal Science Advances.
Flat screen TVs that incorporate quantum dots are now commercially available, but it has been more difficult to create arrays of their elongated cousins, quantum rods, for commercial devices. Quantum rods can control both the polarization and color of light, to generate 3D images for virtual reality devices.
Using scaffolds made of folded DNA, MIT engineers have come up with a new way to precisely assemble arrays of quantum rods. By depositing quantum rods onto a DNA scaffold in a highly controlled way, the researchers can regulate their orientation, which is a key factor in determining the polarization of light emitted by the array. This makes it easier to add depth and dimensionality to a virtual scene.
“One of the challenges with quantum rods is: How do you align them all at the nanoscale so they’re all pointing in the same direction?” says Mark Bathe, an MIT professor of biological engineering and the senior author of the new study. “When they’re all pointing in the same direction on a 2D surface, then they all have the same properties of how they interact with light and control its polarization.”
Quantum computers can solve certain computational problems much faster than ordinary computers by using specific quantum properties. The basic building blocks of such machines are called quantum-bits or qubits. Qubits can be realized using several physical platforms such as nuclear spins, trapped ions, cold atoms, photons, and using superconducting Josephson circuits.
Several such qubits operate in the microwave frequency domain, and require specialized room temperature microwave electronics for control and readout of the quantum states of the qubits. However, there lies a challenge when it comes to connecting classical electronics to these qubits. The qubits need high frequency (GHz) electromagnetic signals for control and readout pulses in the order of a few tens of nanoseconds.
The traditional setup for generation and capture of such signals is often costly and complex with many components. This can be addressed by developing a specific FPGA-based system that brings the functionality of all the traditional equipment on to a single board. However, with such developments, three main challenges need to be kept in mind: generation and capture of the high-fidelity microwave signals, scalability, and a user-friendly interface.
A cosmologist explains the mind-bending hypothesis that our universe could have branched off from a black hole singularity in another universe.
The building blocks of quantum computers are often thought to imitate the famous thought experiment known as Schrödinger’s cat, in which quantum physics essentially suspends a cat in a box in a nebulous state between life and death: The cat only definitely becomes alive or dead when someone looks in the box. Now, by mimicking Schrödinger’s cats as closely as possible, a French startup reveals it could help make extraordinarily powerful quantum computers a reality sooner than previously thought—a strategy Amazon is also pursuing.
The building blocks of quantum computers are often thought to imitate the famous thought experiment known as Schrödinger’s cat, in which quantum physics essentially suspends a cat in a box in a nebulous state between life and death: The cat only definitely becomes alive or dead when someone looks in the box. Now, by mimicking Schrödinger’s cats as closely as possible, a French startup reveals it could help make extraordinarily powerful quantum computers a reality sooner than previously thought—a strategy Classical computers generally switch transistors either on or off to symbolize data as ones or zeroes. In contrast, quantum computers use quantum bits— qubits —that, because of the surreal nature of quantum physics, can exist in a state of superposition where they are both 1 and 0 at the same time. This essentially lets each qubit carry out two calculations simultaneously. The more qubits are quantum-mechanically linked, or entangled, the more calculations they can perform at once, to an exponential degree.
The new strategy depends on so-called “cat states,” pairs of very different quantum states as diametrically opposed to one another as the “alive” and “dead” feline once famously postulated by Erwin Schrödinger.
Defying conventional wisdom, scientists have discovered a novel coupling mechanism involving leaky mode, previously considered unsuitable for high-density integration in photonic circuits.
This surprising discovery paves the way for dense photonic integration, transforming the potential and scalability of photonic chips in areas such as optical computing quantum communication, light detection and ranging (LiDAR), optical metrology, and biochemical sensing.
In a recent Light Science & Application publication, Sangsik Kim, associate professor of electrical engineering at Korea Advanced Institute of Science and Technology (KAIST), and his students at Texas Tech University demonstrated that an anisotropic leaky wave can achieve zero crosstalk between closely spaced identical waveguides using subwavelength grating (SWG) metamaterials.