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June 10, 2025—Researchers create pockets of sound in the air without speakers; the underacknowledged work of an instrumental quantum physics researcher; and why Waymo robotaxis in L.A. burned to dust. —Andrea Gawrylewski, Chief Newsletter Editor | | A Waymo vehicle burns in the middle of an intersection during protests in Los Angeles, Calif., on June 8, 2025. David Pashaee/Middle East Images via AFP | | Physicist Chien-Shiung Wu in her lab at Columbia University in 1978. Lynn Gilbert | | | Overlooked Foundational Physics | In 1949, physicist Chien-Shiung Wu and her graduate student collided positrons and electrons inside a cyclotron particle accelerator and tracked the resulting radiation at the end of the experiment. Their data showed that pairs of photons from the particle collisions remained polarized at right angles to each other, as if somehow connected. It was direct evidence of entanglement, one of the central principles of quantum physics.
Why this is interesting: The 2022 Nobel Prize in physics was awarded to three researchers in entanglement. Although Wu's work couldn't be awarded posthumously (she died in 1997), historians agree that her 1949 experiment was the first to document entangled photons. Her contribution was not mentioned in the 2022 award announcement.
What the experts say: Wu was also excluded during her lifetime from a 1957 Nobel Prize for the discovery that particles inside an atom do not behave symmetrically, as once thought. The researchers who were awarded the prize pleaded for Wu to be acknowledged, since the work was as much hers as their own. Physicist J. Robert Oppenheimer stated publicly that Wu should have shared the prize. The committee did not oblige. | | Soundless Sound How it works: The scientists set up two separate ultrasound emitters, each just over six inches wide. Each was covered with 3D-printed metamaterials, whose tiny grooves shaped the emitters' beams to interfere with each other just as they crossed. The researchers parked a dummy human head in front of these soundless speakers. When one ultrasonic beam that bent to the right and another that bent to the left crossed on the far side of the dummy head, their inaudible sound waves interfered, producing a residual sound at a frequency that humans could hear at the fixed point in space.
What the experts say: "We are not relying on new concepts. But the beauty of this work is that we can combine technologies in very interesting ways," says Yun Jing, an acoustics expert at Pennsylvania State University. "And there are some really interesting applications," he says, ranging from home theaters to device-free communications. | | - Quantum computing undergirds chemistry, biology, engineering and beyond. If we have any hope of creating a technology-literate population and developing a workforce for this emerging field, we need to teach quantum physics in more classrooms, writes Olivia Lanes, North American lead of IBM Quantum Community. Without these efforts, the "more we all stand to lose the immense benefits quantum could bring to our economy, technology and future industries," says Lanes. | 5 min read
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Photographer Lynn Gilbert took the above photo of Chien-Shiung Wu as part of a portrait collection of influential women in 1978. When she first called up Wu to ask to include her in the collection, Wu told her, "I'm not that important." Gilbert, who visited the Columbia University lab where Wu conducted research, described the basement space as a series of messy little rooms off a main corridor, with wires and other equipment all focused around an apparatus in a hole in the floor, framed in wood. "It looked like a giant milk jug," Gilbert told me during a recent interview. In her notes from their 45-minute photo session, Gilbert described Wu as warm, gentle and direct. Wu told her a story from 1957 when she defended her work in physics to a male colleague who had said that women should only be nurses by saying: "Atoms don't know the difference between male and female." | | —Andrea Gawrylewski, Chief Newsletter Editor | | | | |
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