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Category: quantum physics – Page 345

Quantum mechanics: How the future might influence the past

In 2022, the Physics Nobel prize was awarded for experimental work showing that the quantum world must break some of our fundamental intuitions about how the universe works.

Many look at those experiments and conclude that they challenge “locality”—the intuition that distant objects need a physical mediator to interact. And indeed, a mysterious connection between distant particles would be one way to explain these experimental results.

Others instead think the experiments challenge “realism”—the intuition that there’s an objective state of affairs underlying our experience. After all, the experiments are only difficult to explain if our measurements are thought to correspond to something real. Either way, many physicists agree about what’s been called “the death by experiment” of local realism.

MIT discovery rewrites the rules for neutrons and materials

But now, in a wild physics twist, MIT researchers have figured out that neutrons can actually stick to way bigger structures called quantum dots. Quantum dots are like teeny-tiny crystals made up of tens of thousands of atoms. The fact that a single neutron can cling to one is blowing scientists’ minds.

Their findings, published this week in ACS Nano by a team led by professors Ju Li and Paola Cappellaro, could lead to the development of new tools for studying the fundamental properties of materials, including those influenced by the strong nuclear force. This research also holds promise for the creation of entirely new types of quantum information processing devices.

Shielding Quantum Light in Space and Time

A way to create single photons whose spatiotemporal shapes do not expand during propagation could limit information loss in future photonic quantum technologies.

When enjoying the sight of a rainbow, information loss might not be the first thing that comes to mind. Yet dispersion, the underlying process that makes different colors travel at different speeds, also hampers scientists’ control of light propagation—a crucial capability for future photonic quantum technologies. As they move, short laser pulses tend to lengthen through dispersion and widen and dim through diffraction. Together, these effects limit our ability to make light reach a target, although mitigation strategies have been developed for classical pulses and, recently, for quantum light. Now Jianmin Wang at the Southern University of Science and Technology in China and colleagues have realized a quantum source of single photons that are impervious to spreading out during propagation, potentially safeguarding against the loss of information encoded in the photons spatiotemporal shapes [1].

In 2007, physicists demonstrated light beams, known as Airy beams, whose spatial profiles make them resilient to spreading out [2, 3]. These profiles consist of a pattern of bright and dark lobes surrounding a central bright component, with each feature propagating along a parabolic trajectory. Recently, scientists created quantum Airy beams, which are technically challenging to realize [4, 5]. The goal of Wang and colleagues’ work was to extend this principle to the temporal domain, producing quantum Airy single photons that do not spread out in both space and time. Such quantum “light bullets” could offer exciting possibilities for quantum technologies, much like their classical counterparts did for applications in areas from plasma physics to optical trapping [3, 6].

New focused approach can help untangle messy quantum scrambling problems

The world is a cluttered, noisy place, and the ability to effectively focus is a valuable skill. For example, at a bustling party, the clatter of cutlery, the conversations, the music, the scratching of your shirt tag and almost everything else must fade into the background for you to focus on finding familiar faces or giving the person next to you your undivided attention.

Redefining Quantum Communication: Researchers Have Solved a Foundational Problem in Transmitting Quantum Information

Quantum electronics represents a significant departure from conventional electronics. In traditional systems, memory is stored in binary digits. In contrast, quantum electronics utilizes qubits for storage, which can assume various forms, including electrons trapped in nanostructures known as quantum dots. Nonetheless, the ability to transmit information beyond the adjacent quantum dot poses a substantial challenge, thereby limiting the design possibilities for qubits.

Now, in a study recently published in Physical Review Letters, researchers from the Institute of Industrial Science at the University of Tokyo are solving this problem: they developed a new technology for transmitting quantum information over perhaps tens to a hundred micrometers. This advance could improve the functionality of upcoming quantum electronics.

Researchers visualize quantum effects in electron waves

One of the most fundamental interactions in physics is that of electrons and light. In an experiment at Goethe University Frankfurt, scientists have now managed to observe what is known as the Kapitza-Dirac effect for the first time in full temporal resolution. This effect was first postulated more than 90 years ago, but only now are its finest details coming to light.

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