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Category: quantum physics

A team of researchers at Shanghai Jiao Tong University, has found that the human hand can be used as a powerless infrared radiation (IR) source in multiple kinds of applications. In their paper published in Proceedings of the National Academy of Sciences, the group notes that the human hand naturally emits IR and they demonstrate that the radiation can be captured and used.

The emits light in the invisible IR range, including the hands. This source of radiation, the researchers noted, could potentially be captured and used in applications ranging from signal generation to encryption systems. They further noted that because the hand has multiple fingers, the IR that it emits could be considered to be multiplexed.

IR is a form of —its wavelengths are longer than those of , which is why humans cannot see them. Prior research has shown that the human body emits such radiation due to body heat. Electromagnetic radiation carries with it radiant energy, and its behavior is classified as both a quantum particle and a wave. Prior research has also shown that electromagnetic radiation can be used in a variety of applications, including microwaves, radios and medical imaging devices. And , in particular, enables night vision goggles, spectroscopy devices and used to treat burn victims. In this new effort, the researchers have found that the very small amount of IR emitted by the human hand is sufficient to use in various devices.

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In recent years, electronics engineers worldwide have been trying to develop new semiconductor heterostructure devices using atomically thin materials. Among the many devices that can be fabricated using these materials are resonant tunneling diodes, which typically consist of a quantum-well structure placed between two barrier layers.

Past research has shown that stacking two-dimensional (2D) layers that are twisted in relation to each other can enhance or suppress the interlayer coupling at their interface. This suppression or enhancement can in turn modulate the electronic, optical and mechanical properties of the resulting .

For instance, some studies found that the intralayer current transport in small angle twisted bilayer graphene prompted some exotic phenomena, such as superconductivity and ferromagnetism. These observations inspired a fundamentally new approach to device engineering, known as ‘twistronics’ (i.e., twist electronics).

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Researchers have used a quantum mechanical property to overcome some of the limitations of conventional holograms. The new approach, detailed in Nature Physics, employed quantum entanglement, allowing two photons to become a single “non-local particle.” A series of entangled photon pairs is key to producing new and improved holograms.

Classical holograms work by using a single light beam split into two. One beam is sent towards the object you’re recreating and is reflected onto a special camera. The second beam is sent directly onto the camera. By measuring the differences in light, its phase, you can reconstruct a 3D image. A key property in this is the wave’s coherence.

The quantum hologram shares some of these principles but its execution is very different. It starts by splitting a laser beam in two, but these two beams will not be reunited. The key is in the splitting. As you can see in the image below, the blue laser hits a nonlinear crystal, which creates two beams made of pairs of entangled photons.

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Humanity has come a long way in understanding the universe. We’ve got a physical framework that mostly matches our observations, and new technologies have allowed us to analyze the Big Bang and take photos of black holes. But the hypothetical EmDrive rocket engine threatened to upend what we knew about physics… if it worked. After the latest round of testing, we can say with a high degree of certainty that it doesn’t.

If you have memories from the 90s, you probably remember the interest in cold fusion, a supposed chemical process that could produce energy from fusion at room temperature instead of millions of degrees (pick your favorite scale, the numbers are all huge). The EmDrive is basically cold fusion for the 21st century. First proposed in 2001, the EmDrive uses an asymmetrical resonator cavity inside which electromagnetic energy can bounce around. There’s no exhaust, but proponents claim the EmDrive generates thrust.

The idea behind the EmDrive is that the tapered shape of the cavity would reflect radiation in such a way that there was a larger net force exerted on the resonator at one end. Thus, an object could use this “engine” for hyper-efficient propulsion. That would be a direct violation of the conservation of momentum. Interest in the EmDrive was scattered until 2016 when NASA’s Eagelworks lab built a prototype and tested it. According to the team, they detected a small but measurable net force, and that got people interested.

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Using measurements of resistance versus applied gate voltage at temperatures of 390 mK, the researchers showed that superconductivity in the improved NbN layer could survive applied magnetic fields as high as 17.8 Tesla. Meanwhile, the improved GaN semiconductor was of high enough quality to exhibit the quantum Hall effect at lower applied magnetic fields of 15 T. “Both these improvements mean the quantum Hall effect and superconductivity can occur at the same time in the heterostructure over a certain ‘window’ of temperatures and magnetic fields (that is, below 1 K and between magnetic fields of 15 to 17.8 T),” study lead author Phillip Dang tells Physics World.

According to the team, the new GaN/NbN heterostructure could be used in quantum computing and low-temperature electronics. Reporting their work in Science Advances, the researchers say they now plan to further investigate the interaction between superconductivity and the quantum Hall effect in this material.

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A single “super photon” made up of many thousands of individual light particles: About ten years ago, researchers at the University of Bonn produced such an extreme aggregate state for the first time and presented a completely new light source. The state is called optical Bose-Einstein condensate and has captivated many physicists ever since, because this exotic world of light particles is home to its very own physical phenomena.

Researchers led by Prof. Dr. Martin Weitz, who discovered the super photon, and theoretical physicist Prof. Dr. Johann Kroha have returned from their latest “expedition” into the quantum world with a very special observation. They report of a new, previously unknown phase transition in the optical Bose-Einstein condensate. This is a so-called overdamped phase. The results may in the long term be relevant for encrypted quantum communication. The study has been published in the journal Science.

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Michio Kaku is a professor of theoretical physics at City College, New York, a proponent of string theory but also a well-known populariser of science, with multiple TV appearances and several bestselling books behind him. His latest book, The God Equation, is a clear and accessible examination of the quest to combine Einstein’s general relativity with quantum theory to create an all-encompassing “theory of everything” about the nature of the universe.

The physicist on Newton finding inspiration amid the great plague, how the multiverse can unite religions, and why a ‘theory of everything’ is within our grasp.

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About 10 years ago, researchers at the University of Bonn produced an extreme aggregate photon state, a single “super-photon” made up of many thousands of individual light particles, and presented a completely new light source. The state is called an optical Bose-Einstein condensate and has captivated many physicists ever since, because this exotic world of light particles is home to its very own physical phenomena. Researchers led by Prof. Dr. Martin Weitz, who discovered the super photon, and theoretical physicist Prof. Dr. Johann Kroha now report a new observation: a so-called overdamped phase, a previously unknown phase transition within the optical Bose-Einstein condensate. The study has been published in the journal Science.

The Bose-Einstein is an extreme physical state that usually only occurs at very low temperatures. The particles in this system are no longer distinguishable and are predominantly in the same quantum mechanical state; in other words, they behave like a single giant “superparticle.” The state can therefore be described by a single wave function.

In 2010, researchers led by Martin Weitz succeeded for the first time in creating a Bose-Einstein condensate from particles (photons). Their special system is still in use today: Physicists trap light particles in a resonator made of two curved mirrors spaced just over a micrometer apart that reflect a rapidly reciprocating beam of light. The space is filled with a liquid dye solution, which serves to cool down the photons. The dye molecules “swallow” the photons and then spit them out again, which brings the light particles to the temperature of the dye solution—equivalent to room temperature. The system makes it possible to cool light particles because their natural characteristic is to dissolve when cooled.

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