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Scientists Just Simulated Quantum Technology on Classical Computing Hardware
Lurking in the background of the quest for true quantum supremacy hangs an awkward possibility – hyper-fast number crunching tasks based on quantum trickery might just be a load of hype.
Now, a pair of physicists from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Columbia University in the US have come up with a better way to judge the potential of near-term quantum devices – by simulating the quantum mechanics they rely upon on more traditional hardware.
Their study made use of a neural network developed by EPFL’s Giuseppe Carleo and his colleague Matthias Troyer back in 2016, using machine learning to come up with an approximation of a quantum system tasked with running a specific process.
Known as the Quantum Approximate Optimization Algorithm (QAOA), the process identifies optimal solutions to a problem on energy states from a list of possibilities, solutions that should produce the fewest errors when applied.
“There is a lot of interest in understanding what problems can be solved efficiently by a quantum computer, and QAOA is one of the more prominent candidates,” says Carleo.
The QAOA simulation developed by Carleo and Matija Medvidović, a graduate student from Columbia University, mimicked a 54 qubit device – sizeable, but well in line with the latest achievements in quantum tech.
While it was an approximation of how the algorithm would run on an actual quantum computer, it did a good enough job to serve as the real deal.
Time will tell if physicists of the future will be quickly crunching out ground states in an afternoon of QAOA calculations on a bona fide machine, or take their time using tried-and-true binary code.
Engineers are still making incredible headway in harnessing the spinning wheel of probability trapped in quantum boxes. Whether current innovations will ever be enough to overcome the biggest hurdles in this generation’s attempt at quantum technology is the pressing question.
At the core of every quantum processor are units of calculation called qubits. Each represents a wave of probability, one without a single defined state but is robustly captured by a relatively straight-forward equation.
Link together enough qubits – what’s known as entanglement – and that equation becomes increasingly more complex.
As the linked qubits rise in number, from dozens to scores to thousands, the kinds of calculations its waves can represent will leave anything we can manage using classical bits of binary code in the dust.
But the whole process is like weaving a lace rug from spiderweb: Every wave is a breath away from entangling with its environment, resulting in catastrophic errors. While we can reduce the risk of such mistakes, there’s no easy way right now to eliminate them altogether.
However, we might be able to live with the errors if there’s a simple way to compensate for them. For now, the anticipated quantum speedup risks being a mirage physicists are desperately chasing.
“But the barrier of ‘quantum speedup’ is all but rigid and it is being continuously reshaped by new research, also thanks to the progress in the development of more efficient classical algorithms,” says Carleo.
As tempting as it might be to use simulations as a way to argue classical computing retains an advantage over quantum machines, Carleo and Medvidović insist the approximation’s ultimate benefit is to establish benchmarks in what could be achieved in the current era of newly emerging, imperfect quantum technologies.
Beyond that, who knows? Quantum technology is already enough of a gamble. So far, it’s one that seems to be paying off nicely.
This research was published in Nature Quantum Information.
Sunlight Inactivates Coronavirus 8 Times Faster Than Predicted. We Need to Know Why
A team of scientists is calling for greater research into how sunlight inactivates SARS-CoV-2 after realizing there’s a glaring discrepancy between the most recent theory and experimental results.
UC Santa Barbara mechanical engineer Paolo Luzzatto-Fegiz and colleagues noticed the virus was inactivated as much as eight times faster in experiments than the most recent theoretical model predicted.
“The theory assumes that inactivation works by having UVB hit the RNA of the virus, damaging it,” explained Luzzatto-Fegiz.
But the discrepancy suggests there’s something more going on than that, and figuring out what this is may be helpful for managing the virus.
UV light, or the ultraviolet part of the spectrum, is easily absorbed by certain nucleic acid bases in DNA and RNA, which can cause them to bond in ways that are hard to fix.
But not all UV light is the same. Longer UV waves, called UVA, don’t have quite enough energy to cause problems. It’s the mid-range UVB waves in sunlight that are primarily responsible for killing microbes and putting our own cells at risk of Sun damage.
Short-wave UVC radiation has been shown to be effective against viruses such as SARS-CoV-2, even while it’s still safely enveloped in human fluids.
But this type of UV doesn’t usually come into contact with Earth’s surface, thanks to the ozone layer.
“UVC is great for hospitals,” said co-author and Oregon State University toxicologist Julie McMurry. “But in other environments – for instance, kitchens or subways – UVC would interact with the particulates to produce harmful ozone.”
In July 2020, an experimental study tested the effects of UV light on SARS-CoV-2 in simulated saliva. They recorded the virus was inactivated when exposed to simulated sunlight for between 10-20 minutes.
“Natural sunlight may be effective as a disinfectant for contaminated nonporous materials,” Wood and colleagues concluded in the paper.
Luzzatto-Feigiz and team compared those results with a theory about how sunlight achieved this, which was published just a month later, and saw the math didn’t add up.
This study found the SARS-CoV-2 virus was three times more sensitive to the UV in sunlight than influenza A, with 90 percent of the coronavirus’s particles being inactivated after just half an hour of exposure to midday sunlight in summer.
By comparison, in winter light infectious particles could remain intact for days.
Environmental calculations made by a separate team of researchers concluded the virus’s RNA molecules are being photochemically damaged directly by light rays.
This is more powerfully achieved by shorter wavelengths of light, like UVC and UVB. As UVC doesn’t reach Earth’s surface, they based their environmental light exposure calculations on the medium-wave UVB part of the UV spectrum.
“The experimentally observed inactivation in simulated saliva is over eight times faster than would have been expected from the theory,” wrote Luzzatto-Feigiz and colleagues.
“So, scientists don’t yet know what’s going on,” Luzzatto-Fegiz said.
The researchers suspect it’s possible that instead of affecting the RNA directly, long-wave UVA may be interacting with molecules in the testing medium (simulated saliva) in a way that hastens the inactivation of the virus.
Something similar is seen in wastewater treatment – where UVA reacts with other substances to create molecules that damage viruses.
If UVA can be harnessed to combat SARS-CoV-2, cheap and energy-efficient wavelength-specific light sources might be useful in augmenting air filtration systems at relatively low risk for human health.
“Our analysis points to the need for additional experiments to separately test the effects of specific light wavelengths and medium composition,” Luzzatto-Fegiz concludes.
With the ability of this virus to remain suspended in the air for extended periods of time, the safest means to avoid it in countries where it’s running rampant is still social distancing and wearing masks where distancing isn’t possible. But it’s nice to know that sunlight may be helping us out during the warmer months.
Their analysis was published in The Journal of Infectious Diseases.