John Martinis has already revolutionised quantum computing twice. Now, he is working on another radical rethink of the technology that could deliver machines with unrivalled capabilities
Category: quantum physics
A remarkable book on quantum mechanics reveals a really big idea
Where is physics headed? No one knows for sure, but Beyond the Quantum by Antony Valentini is a striking new book that reminds us what a big idea really looks like, finds Jon Cartwright
A Manufacturing Approach That Brings Diamond Quantum Photonics Closer To Industrial Production (MIT, KAUST et al.)
“Foundry-Enabled Patterning of Diamond Quantum Microchiplets for Scalable Quantum Photonics” was published by researchers at MIT, KAUST, PhotonFoundries and MITRE.
Abstract
Quantum technologies promise secure communication networks and powerful new forms of information processing, but building these systems at scale remains a major challenge. Diamond is an especially attractive material for quantum devices because it can host atomic-scale defects that emit single photons and store quantum information with exceptional stability. However, fabricating the optical structures needed to control light in diamond typically relies on slow, bespoke processes that are difficult to scale. In this work, we introduce a manufacturing approach that brings diamond quantum photonics closer to industrial production. Instead of sequentially defining each device by lithography written directly on diamond, we fabricate high-precision silicon masks using commercial semiconductor foundries and transfer them onto diamond via microtransfer printing.
91-qubit Processor Accurately Simulates Many-Body Quantum Chaos
Quantum chaos describes chaotic classical dynamical systems in terms of quantum theory, but simulations of these systems are limited by computational resources. However, one team seems to have found a way by leveraging error mitigation and specialized circuits on a 91-qubit superconducting quantum processor. Their results are published in Nature Physics.
While useful quantum simulations require an ability to eliminate errors, full quantum error correction requires large overheads in qubits and control. Previous work has gotten around this problem by simulating limited quantum many-body systems mostly at smaller scales or with integrable—or less chaotic—models.
The research team involved in the new study opted for a different method. Instead, they used error mitigation, which accepts noise and then corrects errors later, saving computational resources in the process.
A clearer look at critical materials, thanks to refrigerator magnets
With an advanced technology known as angle-resolved photoemission spectroscopy (ARPES), scientists are able to map out a material’s electron energy-momentum relationship, which encodes the material’s electrical, optical, magnetic and thermal properties like an electronic DNA. But the technology has its limitations; it doesn’t work well under a magnetic field. This is a major drawback for scientists who want to study materials that are deployed under or even actuated by magnetic fields.
Inspired by refrigerator magnets, a team of Yale researchers may have found a solution. Their study was featured recently on the cover of The Journal of Physical Chemistry Letters.
Quantum materials —such as unconventional superconductors or topological materials—are considered critical to advancing quantum computing, high-efficiency electronics, nuclear fusion, and other fields. But many of them need to be used in the presence of a magnetic field, or even only become activated by magnetic fields. Being able to directly study the electronic structure of these materials in magnetic fields would be a huge help in better understanding how they work.
Focusing and defocusing light without a lens: First demonstration of the structured Montgomery effect in free space
Applied physicists in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have demonstrated a new way to structure light in custom, repeatable, three-dimensional patterns, all without the use of traditional optical elements like lenses and mirrors. Their breakthrough provides experimental evidence of a peculiar natural phenomenon that had been confined mostly to theory.
Researchers from the lab of Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, report in Optica the first experimental demonstration of the little-known Montgomery effect, in which a coherent beam of light seemingly vanishes, then sharply refocuses itself over and over, in free space, at perfectly placed distances. This lensless, repeatable patterning of light could lay the groundwork for powerful new tools in many areas including microscopy, sensing, and quantum computing.
This effect had been predicted mathematically in the 1960s but never observed under controlled lab conditions. The new work underscores not only that the effect is real, but that it can be precisely engineered and tuned.
Intercity quantum sensor network tightens axion dark matter constraints
Recently, scientists from institutions including the University of Science and Technology of China made a fundamental breakthrough in nuclear-spin quantum precision measurement. They developed the first intercity nuclear-spin-based quantum sensor network, which experimentally constrains the axion topological-defect dark matter and surpasses the astrophysical limits. The study is published in the journal Nature.
Current studies indicate that ordinary visible matter accounts for only about 4.9% of the universe, while dark matter makes up about 26.8%. Axions are among the best-motivated dark matter candidates, and axion fields can form topological defects during phase transitions in the early universe. As Earth crosses topological defects, the defects are expected to interact with nuclear spins and induce signals. However, detection remains a formidable challenge because signals are extremely weak and short-duration.
To overcome the detection challenge, the research team innovatively developed a nuclear-spin quantum precision measurement that “stores” microsecond-scale axion-induced signals in a long-lived nuclear-spin coherent state, enabling a minute-scale readout signal. At the same time, the team used nuclear spin as a quantum spin amplification to further enhance the weak dark-matter signal by at least 100-fold, increasing the sensitivity of spin rotation to about 1 μrad, representing an improvement of more than four orders of magnitude over previous techniques.
Imaging the Wigner crystal state in a new type of quantum material
In some solid materials under specific conditions, mutual Coulomb interactions shape electrons into many-body correlated states, such as Wigner crystals, which are essentially solids made of electrons. So far, the Wigner crystal state remains sensitive to various experimental perturbations. Uncovering their internal structure and arrangement at the atomic scale has proven more challenging.
Researchers at Fudan University have introduced a new approach to study the Wigner crystal state in strongly correlated two-dimensional (2D) systems. They successfully made sub-unit-cell resolution images of the Wigner crystalline state in a carefully engineered material comprised of a single atomic layer of ytterbium chloride (YbCl₃) stacked on graphite.
The research is published in the journal Physical Review Letters.
