Quantum ground states are the states at which quantum systems have the minimum possible energy. Quantum computers are increasingly being used to analyze the ground states of interesting systems, which could in turn inform the design of new materials, chemical compounds, pharmaceutical drugs and other valuable goods.
The reliable preparation of quantum ground states has been a long-standing goal within the physics research community. One quantum computing method to prepare ground states and other desired states is known as adiabatic state preparation.
This is a process that starts from an initial Hamiltonian, a mathematical operator that encodes a system’s total energy and for which the ground state is known, gradually changing it to reach a final Hamiltonian, which encodes the final ground state.
In January, a team led by Jim Schuck, professor of mechanical engineering at Columbia Engineering, developed a method for creating entangled photon pairs, a critical component of emerging quantum technologies, using a crystalline device just 3.4 micrometers thick.
Now, in a paper published in Nature Photonics in October, Columbia Engineers have shrunk nonlinear platforms with high efficiency down to just 160 nanometers by introducing metasurfaces: artificial geometries etched into ultrathin crystals that imbue them with new optical properties.
“We’ve established a successful recipe to pattern ultrathin crystals at the nanoscale to enhance nonlinearity while maintaining their sub-wavelength-thickness,” said corresponding author Chiara Trovatello is currently an assistant professor at Politecnico di Milano and was a Marie Skłodowska-Curie Global Fellow at Columbia working with Schuck.
There are few technologies more fundamental to modern life than the ability to control light with precision. From fiber-optic communications to quantum sensors, the manipulation of photons underpins much of our digital infrastructure. Yet one capability has remained frustratingly out of reach: controlling light with light itself at the most fundamental level using single photons to switch or modulate powerful optical beams.
Now, researchers at Purdue University have achieved this long-sought milestone, demonstrating what they call a “photonic transistor” that operates at single-photon intensities.
Their findings, published in the journal Nature Nanotechnology, report a nonlinear refractive index several orders of magnitude higher than the best-known materials, a leap that could finally make photonic computing practical.
At low temperatures, hydrogen atoms move less like particles and more like waves. This characteristic enables quantum tunneling, the passage of an atom through a barrier with a higher potential energy than the energy of the atom. Understanding how hydrogen atoms move through potential barriers has important industrial applications. However, the small size of hydrogen atoms makes direct observation of their motion extremely challenging.
In a study published in Science Advances, researchers at the Institute of Industrial Science, The University of Tokyo report precise detection of quantum tunneling of hydrogen atoms in palladium metal.
Palladium is a metal that absorbs hydrogen. Palladium atoms are arranged in a repeating three-dimensional cubic pattern, otherwise known as a lattice. Hydrogen atoms can enter this lattice by occupying interstitial sites between the large palladium atoms. These sites are octahedral and tetrahedral in shape. Hydrogen sits stably in an octahedral site and can hop to another octahedral site via a tetrahedral site, which is metastable, i.e., less stable than an octahedral site.
Researchers from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and Johns Hopkins University in Baltimore have achieved a breakthrough in quantum noise characterization in quantum systems—a key step toward reliably managing errors in quantum computing.
Their findings, published in Physical Review Letters, make important strides in addressing a long-standing obstacle to developing useful quantum computers.
Noise in quantum systems can come from traditional sources, like temperature swings, vibration, and electrical interference, as well as from atomic-level activity, like spin and magnetic fields, associated with quantum processing.
A new Swinburne study is addressing a core paradox: if quantum computing is solving problems that cannot be checked by conventional methods, how can we be certain the results are correct? Quantum computing has the potential to tackle problems once thought unsolvable in areas including physics, me
Graphene is a remarkable “miracle” material, consisting of a single, atom-thin layer of tightly connected carbon atoms that remains both stable and highly conductive. These qualities make it valuable for many technologies, including flexible screens, sensitive detectors, high-performance batteries, and advanced solar cells.
A new study, carried out by the University of Göttingen in collaboration with teams in Braunschweig and Bremen in Germany, as well as Fribourg in Switzerland, shows that graphene may be even more versatile than previously believed.
For the first time, researchers have directly identified “Floquet effects” in graphene. This finding settles a long-running question: Floquet engineering – an approach that uses precise light pulses to adjust a material’s properties – can also be applied to metallic and semi-metallic quantum materials like graphene. The work appears in Nature Physics.
Integrating UV lasers is of interest for portable optical clocks and ion-based quantum computers, but material absorption has impeded progress. Here, authors demonstrate a violet integrated laser using UV-transparent materials with mW-level output, narrow linewidth and precise frequency control.
Quantum physicist Vlatko Vedral proposes a radical vision of reality, one in which observers don’t exist, there are no particles and there is no space or time. Instead, for Vedral, quantum numbers, also known as Q numbers, are the true essence of reality, and it’s a much more beautiful and useful way to understand the world.
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