A quantum version of a random access memory can read and write information 1000 times, and could eventually become a key component in long-distance quantum networks.

In conventional computers, random access memory (RAM) is essential for short-term information storage. Random access quantum memory (RAQM) is similar, and the expectation is that it will be vital for the smooth running of an unhackable quantum Internet connecting cities. This is because quantum information degrades easily as it travels – adding RAQMs at…

Quantum computers can now solve problems with real-world applications faster than any ordinary computer, suggesting they could be commercially viable, say researchers at quantum computing firm D-Wave – though outside observers are more cautious.

It had long been hoped that quantum computers will be able to perform some tasks that are impractical or impossible on even the best supercomputers. Google was the first to demonstrate this “quantum supremacy” in 2019, but only for a somewhat contrived benchmark test with no practical use. Indeed, earlier this month, Google …

Google and XPRIZE are launching a $5 million competition to find practical uses for quantum computers that could actually benefit society. We already know that quantum computers can perform specific tasks faster than classical computers, after Google first claimed quantum advantage for its Sycamore processor in 2019. However, these demonstration tasks are simple benchmarks with no real-world applications.

“There’s a lot of rather abstract mathematical problems where we can prove quantum computers give very, very large speed-ups,” says Ryan Babbush at Google. “But a lot of the research community has been less focused on trying to match those more abstract quantum speed-ups to specific real-world applications, and to try to figure out how quantum computers could be used.”

To that end, Google and the XPRIZE Foundation are urging researchers to come up with new quantum algorithms as part of a three-year competition. The winning algorithms could solve an existing problem, like finding a new battery electrolyte that vastly improves storage capacity, but it doesn’t need to solve the problem in practice, says Babbush. Instead, researchers just need to show how an algorithm could be applied, detailing the exact quantum computing specifications required. Alternatively, competitors could show how an existing quantum algorithm could be applied to a real-world problem not previously considered.

The prize will judge entrants’ algorithms on a range of criteria, such as how large their impact could be, whether they tackle problems similar to those outlined in the United Nations Sustainable Development Goals, and how feasibly they can be run on machines that are available now or in the near-future.

A total prize fund of $5 million will be split into a grand prize of $3 million shared between up to three winners, $1 million shared between at most five runners-up and $50,000 for each of 20 semi-finalists.

The prize could help shift the focus of quantum computing researchers from looking at technical definitions of quantum advantage, like those demonstrated by Google or IBM, to real-world uses, says Nicolás Quesada at Montreal Polytechnic in Canada. “[The prize is] hitting the nail on the head that this is a very important problem,” says Quesada. “We need to figure out what to do with a quantum computer.”

However, finding socially beneficial quantum algorithms will require a better understanding of how quantum computers work, such as how to deal with noise and errors, says Bill Fefferman at the University of Chicago. The prize doesn’t address this foundational aspect of building quantum computers, he says.

“I’m very optimistic, in principle, that we’ll find algorithms that are really useful,” Fefferman. “I’m not as optimistic that, in the next three years, we’ll be able to discover those algorithms and then also implement them on the current hardware that will exist.”

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A device that can measure the gravitational force on a particle that weighs less than a grain of pollen could help us understand how gravity works in the quantum world.

Despite keeping you stuck to the ground, gravity is the weakest force we know of. Only very large objects, like planets and stars, produce enough gravitational force to be easily measured. Doing the same for very small objects, on the tiny distances and masses of the quantum realm, is extremely difficult, in part because of the miniscule size of the force, but also because larger objects nearby can overwhelm the signal.

Now Hendrik Ulbricht at the University of Southampton in the UK and his colleagues have developed a new way to measure gravity on small scales by using a tiny neodymium magnet, weighing around 0.5 milligrams, that is levitated by a magnetic field to counteract Earth’s gravity.

Tiny changes in the magnetic field of the magnet created by the gravitational influence of nearby objects can then be converted into a measure of the gravitational force. The whole thing is cooled to almost absolute zero and suspended in a system of springs to minimise outsides forces.

The probe can measure the gravitational tug of objects that weigh just a few micrograms. “You can increase the sensitivity and push the investigation of gravity into a new regime,” says Ulbricht.

He and his team found that, with a 1 kilogram test mass spinning nearby, they could measure a force on the particle of 30 attonewtons. An attonewton is a billionth of a billionth of a newton. One limitation is that the test mass must be in motion at the right speed to create a gravitational resonance with the magnet, otherwise the force won’t be strong enough to be picked up.

The next stage of the experiment will be to shrink the test mass to a similar size as the magnetic particle, so that gravity can be tested while the particles are showing quantum effects like entanglement or superposition. This will be difficult, says Ulbricht, as such small masses will require all other parts of the experiment to be incredibly precise, such as the exact distance between the two particles. Getting to this stage could take at least a decade.

“The fact that they even tried this measurement I find mind-boggling,” says Julian Stirling, a UK-based engineer, due to the difficulty in isolating other gravitational effects from their probe mass. The researchers will need to figure out how to minimise the gravitational influence of the anti-vibrational system, says Stirling, because it seems to have exerted a small but noticeable effect on the levitated particle in this experiment.

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A new type of cooling relies on an exotic quantum mechanical property rather than putting objects into cold environments like refrigerators – and it might one day help us chill things to temperatures lower than any we have reached before.

How cold or warm an object is depends on how its constituent atoms are jiggling, with more and faster jiggling corresponding to more heat and a higher temperature. As such, making objects colder involves finding ways to slow that atomic jiggling –…

A single atom inside of a reflective cavity could be enough to drive a piston in a tiny, quantum version of an engine.

The essential feature of any engine is that it converts heat into work which can then set mechanical parts into motion. For internal combustion engines, burning gas makes it expand and push on and pistons, which eventually results in car wheels or turbine blades moving. Álvaro Tejero at the University of Granada in Spain and…

Nearly a fifth of all difficult-to-correct errors in quantum computers are caused by powerful particles from space hitting the machines. While these cosmic ray-induced errors have long been predicted by scientists, this first precise measurement of how often they occur could help to error proof future devices.

Ordinary computers are also susceptible to cosmic ray errors, but the delicate components that power quantum computers, known as qubits, are more at risk because their fragile quantum states are easily disturbed by…

Time crystals can be used to stabilise fragile states within quantum computers, which could one day give them an edge over traditional computers.

When Nobel laureate Frank Wilczek first theorised that time crystals exist in 2012, the idea was controversial because their defining characteristic is that they flip between two configurations forever without any energy input – a seeming violation of the laws of physics. Since then, however, several research groups have created time crystals in the lab, including inside a quantum…