Reliably quantifying and characterizing the quantum states of various systems is highly advantageous for both quantum physics research and the development of quantum technologies. Quantifying these states typically entails performing several measurements and reconstructing them via a process known as quantum-state tomography.
Electrons can be elusive, but Cornell researchers using a new computational method can now account for where they go—or don’t go—in certain layered materials.
Physics and engineering researchers have confirmed that in certain quantum materials, known as “misfits” because their crystal structures don’t align perfectly—picture LEGOs where one layer has a square grid and the other a hexagonal grid—electrons mostly stay in their home layers.
This discovery, important for designing materials with quantum properties including superconductivity, overturns a long-standing assumption. For years, scientists believed that large shifts in energy bands in certain misfit materials meant electrons were physically moving from one layer to the other. But the Cornell researchers have found that chemical bonding between the mismatched layers causes electrons to rearrange in a way that increases the number of high-energy electrons, while few electrons move from one layer to the other.
Quantum technologies from ultrasensitive sensors to next-generation information processors depend on the ability of quantum bits, or qubits, to maintain their delicate quantum states for a sufficiently long time to be useful.
One of the most important measures of this stability is the spin coherence time. Unfortunately, qubits may lose coherence because their environment is “noisy,” for example, due to the presence of nuclear isotopes or other interference that disturbs the qubit.
Two-dimensional (2D) materials—or atomically thin sheets—can offer quiet environments for qubits, as their reduced thickness naturally lowers the number of isotopes that interact with the qubit.
A team from the Faculty of Physics and the Center for Quantum Optica l Technologies at the Center of New Technologies, University of Warsaw has developed a new method for measuring elusive terahertz signals using a “quantum antenna.”
The authors of the work utilized a novel setup for radio wave detection with Rydberg atoms to not only detect but also precisely calibrate a so-called frequency comb in the terahertz band. This band was until recently a white spot in the electromagnetic spectrum, and the solution described in the journal Optica paves the way for ultrasensitive spectroscopy and a new generation of quantum sensors operating at room temperature.
Terahertz (THz) radiation, being part of the electromagnetic spectrum, lies at the boundary of electronics and optics, positioned between microwaves (used, for example, in Wi-Fi) and infrared.
Trapped neutral atoms are an attractive platform for quantum computing, as large arrays of atomic qubits can be arranged and manipulated to perform gate operations. However, the loss of useable atoms—either from escape or from disturbance—can be a limitation for long computations with repeated measurements. Researchers at Atom Computing, a company in California, have devised a “reset or reload” protocol that mitigates atom losses [1]. The method was successfully employed during a computation consisting of 41 cycles of qubit measurements.
All current quantum computers require error correction, which involves measuring certain qubits at intermediate steps of a computation. Reusing these qubits would avoid needing a prohibitively high overhead in qubit numbers, says team member Matthew Norcia. But in the case of atoms, the process of resetting measured qubits risks disturbing unmeasured ones.
To overcome this challenge, the researchers have developed a way to shield unmeasured atoms from the resetting process. They use targeted laser beams to immunize the unmeasured atoms against excitation by shifting their resonances. They then turn on a second set of lasers that cool the measured atoms and reinitialize them, enabling them to join the unmeasured atoms in the next computational step.
Researchers from the School of Physics at Wits University, working with collaborators from the Universitat Autònoma de Barcelona, have demonstrated how quantum light can be engineered in space and time to create high-dimensional and multidimensional quantum states. Their work highlights how structured photons—light whose spatial, temporal or spectral properties are deliberately shaped—offer new pathways for high-capacity quantum communication and advanced quantum technologies.
Published as a review article in Nature Photonics, the study surveys rapid progress in techniques capable of creating, manipulating and detecting quantum structured light. These include on-chip integrated photonics, nonlinear optics, and multiplane light conversion, which now form a modern and increasingly powerful toolkit. Together, these advances are bringing structured quantum states closer to real-world applications in imaging, sensing, and quantum networks.
