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Category: quantum physics – Page 430

Researchers in Brazil have achieved a quantum breakthrough by succeeding in the creation of a source of illumination that produces two separate entangled beams of light, according to new research.

The achievement was announced by a team of physicists with Brazil’s Laboratory for Coherent Manipulation of Atoms and Light (LMCAL), located at the University of São Paulo’s Physics Institute.

Quantum entanglement is among the most perplexing phenomena observed in modern physics. It involves particles that are linked in such a way that when changes affect the quantum state of one, the other to which it is “entangled” will also be affected. Strangely, such effects even occur over significant distances, a phenomenon first described as “spooky action at a distance” after its discussion in a landmark 1935 paper by Albert Einstein, Boris Podolsky, and Nathan Rosen.

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Everything you ever wanted to know about parallel universes, time, entropy, free will and more, explained by physicist Sean Carroll.

Up next, Michio Kaku: The Universe in a nutshell (Full Presentation) ► https://youtu.be/0NbBjNiw4tk.

Do you have free will? Is our Universe the only one, or do we live in one of many? And what does Einstein’s theory of relativity really say about the nature of reality?

These are some of the big questions that theoretical physicist Sean Carroll tackles in this Big Think video.

In 2022, Carroll published The Biggest Ideas in the Universe: Space, Time, and Motion, a book that achieves that rare feat of detailing the inner workings of scientific concepts in a way that’s accessible but not overly simplistic.

THE MULTIVERSE

Continue reading “The Universe in 90 minutes: Time, free will, God, & more | Sean Carroll” | >

Taming rays of light and bending them to your will is tricky business. Light travels fast and getting a good chunk of it to stay in one place for a long time requires a lot of skillful coaxing. But the benefits of learning how to hold a moonbeam (or, more likely, a laser beam) in your hand, or on a convenient chip, are enormous. Trapping and controlling light on a chip can enable better lasers, sensors that help self-driving cars “see,” the creation of quantum-entangled pairs of photons that can be used for secure communication, and fundamental studies of the basic interactions between light and atoms—just to name a few.

Of all the moonbeam-holding chip technologies out there, two stand the tallest: the evocatively named whispering gallery mode microrings, which are easy to manufacture and can trap light of many colors very efficiently, and photonic crystals, which are much trickier to make and inject light into but are unrivaled in their ability to confine light of a particular color into a tiny space—resulting in a very large intensity of light for each confined photon.

Recently, a team of researchers at JQI struck upon a clever way to combine whispering gallery modes and photonic crystals in one easily manufacturable device. This hybrid device, which they call a microgear photonic crystal ring, can trap many colors of light while also capturing particular colors in tightly confined, high-intensity bundles. This unique combination of features opens a route to new applications, as well as exciting possibilities for manipulating light in novel ways for basic research.

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For the first time, physicists at the Brookhaven National Laboratory have come across a novel type of quantum entanglement, the extremely bizarre phenomenon that occurs when a pair of particles remain connected even when separated by galactic distances. Thanks to this effect, the researchers were also able to peer inside the atomic nuclei with unprecedented detail.

Quantum entanglement is a strange and fascinating phenomenon that has puzzled scientists for decades. It occurs when pairs of particles become so closely connected that one can no longer be described without the other, no matter how far apart they may be. Even more strange, changing one will instantly trigger a change in its partner, even if it was on the other side of the universe. In theory, this effect would enable faster-than-light communication if you encode the changes in these states with 1s and 0s.

This concept may sound impossible to us, as it goes against our classical understanding of physics, and it even unnerved Albert Einstein, who referred to it as “spooky action at a distance.” However, numerous experiments have consistently proven the existence of quantum entanglement by manipulating the properties of the entangled particles, such as their spin or polarization, and observing the effects on the other particle. Today, quantum entanglement forms the backbone of emerging technologies such as quantum computers and networks.

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Over the past few decades, several imaging protocols based on quantum technologies have been realized1,2, which have expanded the application capabilities of optical imaging. These include ghost imaging (GI)3,4, quantum imaging with undetected photons (QIUP)5, and interaction-free measurements (IFMs)6,7. The quantum GI scheme relies on the spatial correlations of entangled photon pairs and requires two-photon coincident measurements. Furthermore, ghost imaging can also be realized with classical intensity-fluctuation correlations8. Later, various single-pixel imaging (SPI) protocols were proposed9,10,11,12,13, where the spatial correlations are not between two photons but between one photon and a programmable mask held in a spatial light modulator (SLM).

In contrast to modern digital cameras employing array sensors to capture images, SPI use a sequence of masks to interrogate the scene along with the correlated intensity measurements by a single-pixel detector. The spatially resolved masks are usually generated by computer and displayed by SLM. Combined with compressive techniques10, the number of sampling measurements is fewer than the total number of pixels in the image. Thereby, SPI can reduce the data processing requirement, and shows potential capability for high dimensional sensing12. On the other hand, the modern single-photon detector is featured by improved detection efficiency, lower dark counts, and faster timing response14. Such enhancements have significance to applying SPI into weak signal detection scenarios, such as scattering medium imaging or long-range 3D imaging11.

The QIUP scheme is based on induced coherence (IC), which was first proposed by Zou, Wang, and Mandel15. They used two photon sources to generate photon pairs. By overlapping path of two sources for one photon (idler)15,16,17 and establishing the so-called path identity18,19, there is no information about the origin of the other photon (signal). Thus, the signal photon is in the superposition state of being created in either of the sources. The phase and transmissivity of the idler photon are encoded in the interference of the signal photon. Inserting one object onto the idler path between two sources, one can obtain images exclusively with the signal photons which have no interaction with the object5. In contrast to GI, QIUP does not involve the detection of the photon illuminating the object or any coincidence measurement. This is an advantage of QIUP, as the wavelength of the detected photon can be chosen independently from that of the photon interacting with the object5. This concept was further explored in infrared (IR) spectroscopy20, optical coherence tomography21,22, mid-IR imaging23,24,25, terahertz (THz) sensing26, biological microscopy27, and holography28. Recently, the related SU(1,1) interferometer has been investigated and employed in quantum-enhanced metrology29,30,31,32,33.

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Researchers demonstrated high-visibility quantum interference between two independent semiconductor quantum dots — an important step toward scalable quantum networks.

Last year’s Nobel Prize in Physics celebrated the fundamental interest of quantum entanglement, and also envisioned the potential applications in “the second quantum revolution” — a new age when we are able to manipulate the weirdness of quantum mechanics, including quantum superposition and entanglement. A large-scale and fully functional quantum network is the holy grail of quantum information sciences. It will open a new frontier of physics, with new possibilities for quantum computation, communication, and metrology.

One of the most significant challenges is to extend the distance of quantum communication to a practically useful scale. Unlike classical signals that can be noiselessly amplified, quantum states in superposition cannot be amplified because they cannot be perfectly cloned. Therefore, a high-performance quantum network requires not only ultra-low-loss quantum channels and quantum memory, but also high-performance quantum light sources. There has been exciting recent progress in satellite-based quantum communications and quantum repeaters, but a lack of suitable single-photon sources has hampered further advances.

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Positively and negatively charged versions of the same particle have been entangled for the first time, allowing us to map the hearts of atoms more precisely and opening the doors to more powerful communication tools.

The neutrons and protons that make up the nuclei of atoms are, in turn, composed of quarks. However, quarks alone would be unstable; they need gluons, the carriers of the strong force, to hold them together. Gluons are orders of magnitude too small to see, even with the most powerful microscopes – but they can still interact with photons to produce exceptionally short-lived rho particles that decay to charged two-quark particles called pions.

By measuring the angles and speed at which the positive and negative pions (π+ and π-) emerge, scientists at the Brookhaven National Laboratory have created a map of gluon distribution within the nuclei of gold and uranium atoms. They report this map to be the most precise description of the inner workings of an atomic nucleus.

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