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Google says it expects to reach an important milestone for quantum computing this year. Not so fast, says Alibaba.

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How the nature of cause and effect will determine the future of quantum technology.

An unprecedented, global-scale test of one of quantum theory’s most counterintuitive predictions sheds new light on the nature of reality and how we can exploit it with quantum technologies.

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Time feels real to people. But it doesn’t even exist, according to quantum physics. “There is no time variable in the fundamental equations that describe the world,” theoretical physicist Carlo Rovelli tells Quartz.

If you met him socially, Rovelli wouldn’t assault you with abstractions and math to prove this point. He’d “rather not ruin a party with physics,” he says. We don’t have to understand the mechanics of the universe to go about our daily lives. But it’s good to take a step back every once in a while.

“Time is a fascinating topic because it touches our deepest emotions. Time opens up life and takes everything away. Wondering about time is wondering about the very sense of our life. This is [why] I have spent my life studying time,” Rovelli explains.

Continue reading “This physicist’s ideas of time will blow your mind” »

While a variety of quantum systems exist today, many are unable to scale to solve some of the world’s most challenging problems. Explaining the real-world obstacles of building a quantum system that scales, this post explores how Microsoft addresses these challenges through a topological qubit.

New research gives insight into a recent experiment that was able to manipulate an unprecedented number of atoms through a quantum simulator. This new theory could provide another step on the path to creating the elusive quantum computers.

Quantum theory is based heavily on probabilities, since measuring a quantum system doesn’t produce the same outcome every time, but instead yields one of many outcomes that each occur with a certain probability. Now in a new paper, physicists have presented a new quantum probability rule for assigning probabilities to measurement outcomes, or events, that essentially combines two of the most important quantum probability rules (the Born rule and the wave function collapse rule) into one.

The physicists, Sally Shrapnel, Fabio Costa, and Gerard Milburn, at The University of Queensland in Australia, have published a paper on the new quantum probability rule in the New Journal of Physics.

One of the most important probability rules in quantum theory is the Born rule, which gives the probability that a measurement yields a certain event. However, things get a little bit more complicated when predicting consecutive events. Although in classical scenarios it’s possible to assign joint probabilities to consecutive events using conditioning, in quantum scenarios this is not possible since each measurement necessarily disturbs the system. So in quantum mechanics, the state must be updated with this new information after every measurement.

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Superconductors are among the most bizarre and exciting materials yet discovered. Counterintuitive quantum-mechanical effects mean that, below a critical temperature, they have zero electrical resistance. This property alone is more than enough to spark the imagination.

A current that could flow forever without losing any energy means transmission of power with virtually no losses in the cables. When renewable energy sources start to dominate the grid and high-voltage transmission across continents becomes important to overcome intermittency, lossless cables will result in substantial savings.

What’s more, a superconducting wire carrying a current that never, ever diminishes would act as a perfect store of electrical energy. Unlike batteries, which degrade over time, if the resistance is truly zero, you could return to the superconductor in a billion years and find that same old current flowing through it. Energy could be captured and stored indefinitely!

Continue reading “Why the Discovery of Room-Temperature Superconductors Would Unleash Amazing Technologies” »

Realizing Majorana bound states (MBS) in condensed matter systems is a key challenge on the way toward topological quantum computing. As a promising platform, one-dimensional magnetic chains on conventional superconductors were theoretically predicted to host MBS at the chain ends. We demonstrate a novel approach to design of model-type atomic-scale systems for studying MBS using single-atom manipulation techniques. Our artificially constructed atomic Fe chains on a Re surface exhibit spin spiral states and a remarkable enhancement of the local density of states at zero energy being strongly localized at the chain ends. Moreover, the zero-energy modes at the chain ends are shown to emerge and become stabilized with increasing chain length. Tight-binding model calculations based on parameters obtained from ab initio calculations corroborate that the system resides in the topological phase. Our work opens new pathways to design MBS in atomic-scale hybrid structures as a basis for fault-tolerant topological quantum computing.

Majorana fermions —particles being their own antiparticles—have recently attracted renewed interest in various fields of physics. In condensed matter systems, Majorana bound states (MBS) with a non-Abelian quantum exchange statistics have been proposed as a key element for topological quantum computing (2–4). One of the most promising platforms to realize MBS are one-dimensional (1D) helical spin systems being proximity-coupled to a conventional s-wave superconductor (5–9). In such a surface-confined system, the MBS can directly be investigated by local probe techniques such as scanning tunneling microscopy/spectroscopy (STM/STS). Previously reported experiments aiming at the direct visualization and probing of the MBS have focused on self-assembled magnetic chains on superconducting Pb substrates (10–15).

China is moving ahead on quantum technology.