An experiment with an acoustic resonator demonstrates the quantum superposition of atoms—nearly matching the ability of matter interferometers to test quantumness on macroscopic scales.
Category: particle physics – Page 375
A robust quantum memory that stores information in a trapped-ion quantum network
Researchers at University of Oxford have recently created a quantum memory within a trapped-ion quantum network node. Their unique memory design, introduced in a paper in Physical Review Letters, has been found to be extremely robust, meaning that it could store information for long periods of time despite ongoing network activity.
“We are building a network of quantum computers, which use trapped ions to store and process quantum information,” Peter Drmota, one of the researchers who carried out the study, told Phys.org. “To connect quantum processing devices, we use single photons emitted from a single atomic ion and utilize quantum entanglement between this ion and the photons.”
Trapped ions, charged atomic particles that are confined in space using electromagnetic fields, are a commonly used platform for realizing quantum computations. Photons (i.e., the particles of light), on the other hand, are generally used to transmit quantum information between distant nodes. Drmota and his colleagues have been exploring the possibility of combining trapped ions with photons, to create more powerful quantum technologies.
Why black holes unlock the quantum majesty of the Universe
The story of modern physics has been one of reductionism. We do not need a vast encyclopedia to understand the inner workings of Nature. Rather, we can describe a near-limitless range of natural phenomena, from the interior of a proton to the creation of galaxies, with apparently unreasonable efficiency using the language of mathematics. In the words of theoretical physicist Eugene Wigner, ‘The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve. We should be grateful for it.’
The mathematics of the twentieth century described a Universe populated by a limited number of different types of fundamental particles interacting with each other in an arena known as spacetime according to a collection of rules that can be written down on the back of an envelope. If the Universe was designed, it seemed, the designer was a mathematician.
Today, the study of black holes appears to be edging us in a new direction, towards a language more often used by quantum computer scientists. The language of information. Space and time may be emergent entities that do not exist in the deepest description of Nature. Instead, they are synthesized out of entangled quantum bits of information in a way that resembles a cleverly constructed computer code. If the Universe is designed, it seems, the designer is a programmer.
Scientists figured out how to manipulate ‘quantum light’ for the first time in history
Manipulating anything in the world of quantum physics is tricky, but now, scientists have managed to manipulate quantum light particles that have a strong relationship with each other. The breakthrough sounds a bit obscure, especially if you aren’t studying quantum mechanics yourself, but it’s a huge success that will be fundamental in how scientists study the quantum realm from here forward.
Nonlinear evolution of the Weibel instability with relativistic laser pulses
The Weibel instability is investigated using relativistic intense short laser pulses. A relativistic short laser pulse can generate a sub-relativistic high-density collisionless plasma. By irradiating double parallel planar targets with two relativistic laser pulses, sub-relativistic collisionless counterstreaming plasmas are created. Since the growth rate of the Weibel instability is proportional to the plasma density and velocity, the spatial and temporal scales of the Weibel instability can be much smaller than that from nanosecond large laser facilities. Recent theoretical and numerical studies have revealed that astrophysical collisionless shocks in sub-relativistic regimes in the absence and presence of an ambient magnetic field play essential roles in cosmic ray acceleration. With experimental verification in mind, we discuss the possible experimental models on the Weibel instability with intense short laser pulses. In order to show the experimental feasibility, we perform 2D particle-in-cell simulations in the absence of an external magnetic field as the first step and discuss the optimum conditions to realize the nonlinear evolutions of the Weibel instability in laboratories.
New LHC experiments enter uncharted territory
Although neutrinos are produced abundantly in collisions at the Large Hadron Collider (LHC), until now no neutrinos produced in such a way had been detected. Within just nine months of the start of LHC Run 3 and the beginning of its measurement campaign, the FASER collaboration changed this picture by announcing its first observation of collider neutrinos at this year’s electroweak session of the Rencontres de Moriond. In particular, FASER observed muon neutrinos and candidate events of electron neutrinos. “Our statistical significance is roughly 16 sigma, far exceeding 5 sigma, the threshold for a discovery in particle physics,” explains FASER’s co-spokesperson Jamie Boyd.
In addition to its observation of neutrinos at a particle collider, FASER presented results on searches for dark photons. With a null result, the collaboration was able to set limits on previously unexplored parameter space and began to exclude regions motivated by dark matter. FASER aims to collect up to ten times more data over the coming years, allowing more searches and neutrino measurements.
FASER is one of two new experiments situated at either side of the ATLAS cavern to detect neutrinos produced in proton collisions in ATLAS. The complementary experiment, SND@LHC, also reported its first results at Moriond, showing eight muon neutrino candidate events. “We are still working on the assessment of the systematic uncertainties to the background. As a very preliminary result, our observation can be claimed at the level of 5 sigma,” adds SND@LHC spokesperson Giovanni De Lellis. The SND@LHC detector was installed in the LHC tunnel just in time for the start of LHC Run 3.
A cavity leads to a strong interaction between light and matter
Researchers have succeeded in creating an efficient quantum-mechanical light-matter interface using a microscopic cavity. Within this cavity, a single photon is emitted and absorbed up to 10 times by an artificial atom. This opens up new prospects for quantum technology, report physicists at the University of Basel and Ruhr-University Bochum in the journal Nature.
Quantum physics describes photons as light particles. Achieving an interaction between a single photon and a single atom is a huge challenge due to the tiny size of the atom. However, sending the photon past the atom several times by means of mirrors significantly increases the probability of an interaction.
In order to generate photons, the researchers use artificial atoms, known as quantum dots. These semiconductor structures consist of an accumulation of tens of thousands of atoms, but behave much like a single atom: when they are optically excited, their energy state changes and they emit a photon. “However, they have the technological advantage that they can be embedded in a semiconductor chip,” says Dr. Daniel Najer, who conducted the experiment at the Department of Physics at the University of Basel.
Beaming in a Spin Texture
Researchers use an optical vortex beam to create a stable pattern of electron spins in a thin layer of semiconductor material.
Spin-based electronic, or “spintronic,” devices can benefit from techniques that coax electron spins into static spatial patterns called spin textures. A new experiment demonstrates that an optical vortex—a light beam that carries orbital angular momentum—can generate a stable spin texture in a semiconductor [1]. The research team showed that the vortex generates a pattern of stripes that has potential uses in processing spin information. Previous experiments have optically stimulated these striped textures, but the optical vortex has a structure that approximately overlaps with the stripe pattern, allowing faster spin-texture formation.
The spins of unbound electrons in a material can be aligned by a magnetic field or by polarized light. But as these electrons move—either through diffusion or through conduction—their spins will begin to rotate in response to so-called spin-orbit interactions within the material. The direction and rate of these rotations for any given electron depend on the path that it takes. Thus, two nearby electrons that start out aligned will become misaligned as they move along different paths, even if they arrive at the same destination. So maintaining an electronic spin texture seems like a doomed enterprise.
Graphene grows—physicists find a way to visualize it
Graphene is one of the strongest materials. On top of that, it is exceptionally good at conducting heat and electrical currents, making it one of the most special and versatile materials we know. For all these reasons, the discovery of graphene was awarded the Nobel Prize in Physics in 2010.
Yet, many properties of the material and its cousins are still poorly understood—for the simple reason that the atoms they are made up of are very difficult to observe. A team of researchers from the University of Amsterdam and New York University have now found a surprising way to solve this issue.
Two-dimensional materials, consisting of a hyper-thin single layer of atomic crystal, have attracted a lot of attention recently. This well-deserved attention is mainly due to their unusual properties, very different from their three-dimensional ‘bulk’ counterparts. Graphene, the most famous representative, and many other two-dimensional materials, are nowadays researched intensely in the laboratory.
New experiment translates quantum information between technologies in an important step for the quantum internet
Researchers have discovered a way to “translate” quantum information between different kinds of quantum technologies, with significant implications for quantum computing, communication, and networking.
The research was published in the journal Nature on Wednesday. It represents a new way to convert quantum information from the format used by quantum computers to the format needed for quantum communication.
Photons—particles of light—are essential for quantum information technologies, but different technologies use them at different frequencies. For example, some of the most common quantum computing technology is based on superconducting qubits, such as those used by tech giants Google and IBM; these qubits store quantum information in photons that move at microwave frequencies.