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Category: quantum physics – Page 734

Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.

Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring rather antithetical properties, has been long sought in . However, after decades of theoretical and experimental efforts, an unambiguous proof of supersolidity in these systems is still missing. Two research teams led by Francesca Ferlaino, one at the Institute for Experimental Physics at the University of Innsbruck and one at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, now report on the observation of hallmarks of this exotic state in ultracold atomic gases.

While so far most work has focused on helium, researchers have recently turned to atomic gases—in particular, those with strong dipolar interactions. The team of Francesca Ferlaino has been investigating quantum gases made of atoms with a strong dipolar character for a long time. “Recent experiments have revealed that such gases exhibit fundamental similarities with superfluid helium,” says Lauriane Chomaz, referring to experimental achievements in Innsbruck and in Stuttgart over the last few years. “These features lay the groundwork for reaching a state where the several tens of thousands of particles of the gas spontaneously organize in a self-determined crystalline structure while sharing the same macroscopic wavefunction—hallmarks of supersolidity.”

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To a non-physicist, an “atomic beam collimator” may sound like a phaser firing mystical particles. That might not be the worst metaphor to introduce a technology that researchers have now miniaturized, making it more likely to someday land in handheld devices.

Today, atomic collimators are mostly found in physics labs, where they shoot out atoms in a beam that produces exotic quantum phenomena and which has properties that may be useful in precision technologies. By shrinking collimators from the size of a small appliance to fit on a fingertip, researchers at the Georgia Institute of Technology want to make the technology available to engineers advancing devices like or accelerometers, a component found in smartphones.

“A typical device you might make out of this is a next-generation gyroscope for a precision navigation system that is independent of GPS and can be used when you’re out of satellite range in a remote region or traveling in space,” said Chandra Raman, an associate professor in Georgia Tech’s School of Physics and a co-principal investigator on the study.

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A team of researchers at NTT Corporation has developed a way to use light-based computer hardware that allows it to to compete with silicon. In their paper published in the journal Nature Photonics, the group describes their research, the devices they created and how well they worked.

Computer scientists have known for some time that the era of increasing speed by modifying silicon-based computer parts is coming to an end. To that end, many have turned to quantum computing as the way to speed up computers—but to date, such efforts have not led to useful machines and there is no guarantee they ever will. Because of that, others in the are looking for other options, such as using to move data around inside of computers instead of electrons. Currently, light is generally only used to carry data long distances. In this new effort, the researchers report that they have developed computing devices based partially on light that performed as well as electron-based hardware.

The idea of using only light as a data medium in is still a long way off—instead, engineers are focusing on using light in areas where it seems feasible and electrons everywhere else. Because of that computer devices must be able to convert between the two mediums, a problem that until now has prevented such devices from being built. Prior efforts have required too much power to be feasible and the conversion process has been too slow. To get around both problems, the researchers developed a new kind of photonic crystal that was able to diffuse light in a way that allowed it to follow a designated path on demand and to also be absorbed when needed to be used for generating current. The crystal was also able to work in reverse.

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Simulations of stochastic processes play an important role in the quantitative sciences, enabling the characterisation of complex systems. Recent work has established a quantum advantage in stochastic simulation, leading to quantum devices that execute a simulation using less memory than possible by classical means. To realise this advantage it is essential that the memory register remains coherent, and coherently interacts with the processor, allowing the simulator to operate over many time steps. Here we report a multi-time-step experimental simulation of a stochastic process using less memory than the classical limit. A key feature of the photonic quantum information processor is that it creates a quantum superposition of all possible future trajectories that the system can evolve into. This superposition allows us to introduce, and demonstrate, the idea of comparing statistical futures of two classical processes via quantum interference. We demonstrate interference of two 16-dimensional quantum states, representing statistical futures of our process, with a visibility of 0.96 ± 0.02.

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For the first time, Yale physicists have directly observed quantum behavior in the vibrations of a liquid body.

A great deal of ongoing research is currently devoted to discovering and exploiting quantum effects in the motion of macroscopic objects made of solids and gases. This new experiment opens a potentially rich area of further study into the way quantum principles work on liquid bodies.

The findings come from the Yale lab of physics and applied physics professor Jack Harris, along with colleagues at the Kastler Brossel Laboratory in France. A study about the research appears in the journal Physical Review Letters.

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Maxwell’s demon is a machine proposed by James Clerk Maxwell in 1897. The hypothetical machine would use thermal fluctuations to obtain energy, apparently violating the second principle of thermodynamics. Now, researchers at the University of Barcelona have presented the first theoretical and experimental solution of a continuous version of Maxwell’s demon in a single molecule system. The results, published in the journal Nature Physics, have applications in other fields, such as biological and quantum systems.

“Despite its simplicity and the large amount of work in the field, this new variant of the classical Maxwell demon has remained unexplored until now,” notes F\xE8lix Ritort, professor from the Department of Fundamental Physics of the UB. “In this study, we introduced a system able to extract large amounts of work arbitrarily per cycle through repeated measurements of the state of a system.”

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We usually think of microwaves as waves that heat things up, usually leftover food, but did you know that they can also cool things down? For example, physicists recently decided to use them to freeze atoms, and attempts have been very successful: They managed to cool them down to within a millionth of a degree of absolute zero (–273.15°C or −459.67°F).

The University of Sussex team, led by Winifried Hensinger, had their results published in Physical Review Letters.

“The use of long-wavelength radiation instead of laser technology to cool ions can tremendously simplify the construction of practical quantum technology devices enabling us to build real devices much faster,” said Professor Hensinger.

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The goal of a worldwide “quantum internet” could be one step closer thanks to new experiments by researchers in Japan and Canada who have made the first ever quantum repeaters that work using an all-photonic protocol. The scheme importantly allows for the time-reversed adaptive Bell measurement, which is a key component for all-photonic quantum repeaters. It is based on optical devices alone and does not require any quantum memories or quantum error correction.

The Internet as we know it was not designed to be secure, and hacking, break-ins and espionage are unfortunately par for the course today. A quantum internet would be much more secure – as well as being much faster – since it exploits key features of quantum physics such as quantum entanglement.

Entanglement and quantum memories.

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