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Unequivocally demonstrating that a quantum computer can significantly outperform any existing classical computers will be a milestone in quantum science and technology. Recently, groups at Google and at the University of Science and Technology of China (USTC) announced that they have achieved such quantum computational advantages. The central quantity of interest behind their claims is the linear cross-entropy benchmark (XEB), which has been claimed and used to approximate the fidelity of their quantum experiments and to certify the correctness of their computation results. However, such claims rely on several assumptions, some of which are implicitly assumed. Hence, it is critical to understand when and how XEB can be used for quantum advantage experiments. By combining various tools from computer science, statistical physics, and quantum information, we critically examine the properties of XEB and show that XEB bears several intrinsic vulnerabilities, limiting its utility as a benchmark for quantum advantage.

Concretely, we introduce a novel framework to identify and exploit several vulnerabilities of XEB, which leads to an efficient classical algorithm getting comparable XEB values to Google’s and USTC’s quantum devices (2% 12% of theirs) with just one GPU within 2 s. Furthermore, its performance features better scaling with the system size than that of a noisy quantum device. We observe that this is made possible because the XEB can highly overestimate the fidelity, which implies the existence of “shortcuts” to achieve high XEB values without simulating the system. This is in contrast to the intuition of the hardness of achieving high XEB values by all possible classical algorithms.

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Nanoparticles (NPs) administered in the human body will undergo rapid surface modification upon contact with biological fluids driven by their interfacial interaction with a diverse range of biomolecules. Such spontaneous self-assembly and adsorption of proteins and other biomolecules onto the NP surface constitute what is commonly known as the protein or biomolecule corona. This surface biotransformation of the NPs modulates their biological interactions and impact on physiological systems and can influence their overall pharmacological profile. Here, we comment on how the initially considered ‘nuisance’ of the in vivo corona formation can now be considered a nanoparticle engineering tool for biomedical use, such as in endogenous tissue targeting, personalized biomarker discovery and immunomodulation.

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There is no doubt that water is significant. Without it, life would never have begun, let alone continue today—not to mention its role in the environment itself, with oceans covering over 70% of Earth.

But despite its ubiquity, liquid water features some electronic intricacies that have long puzzled scientists in chemistry, physics, and technology. For example, the , i.e., the energy stabilization undergone by a free electron when captured by water, has remained poorly characterized from an experimental point of view.

Even today’s most accurate electronic structure has been unable to clarify the picture, which means that important physical quantities like the energy at which electrons from external sources can be injected in liquid water remain elusive. These properties are crucial for understanding the behavior of electrons in water and could play a role in , environmental cycles, and technological applications like solar energy conversion.

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The question of where the boundary between classical and quantum physics lies is one of the longest-standing pursuits of modern scientific research, and in new research published today, scientists demonstrate a novel platform that could help us find an answer.

The laws of quantum physics govern the behavior of particles at miniscule scales, leading to phenomena such as , where the properties of entangled particles become inextricably linked in ways that cannot be explained by classical physics.

Research in quantum physics helps us to fill gaps in our knowledge of physics and can give us a more complete picture of reality, but the tiny scales at which operate can make them difficult to observe and study.

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Gravitationally speaking, the universe is a noisy place. A hodgepodge of gravitational waves from unknown sources streams unpredictably around space, including possibly from the early universe.

Scientists have been looking for signs of these early cosmological , and a team of physicists have now shown that such waves should have a distinct signature due to the behavior of quarks and gluons as the universe cools. Such a finding would have a decisive impact on which models best describe the universe almost immediately after the Big Bang. The study is published in the journal Physical Review Letters.

Scientists first found direct evidence for gravitational waves in 2015 at the LIGO gravitational wave interferometers in the US. These are singular (albeit tiny amplitude) waves from a particular source, such as the merger of two black holes, which wash past Earth. Such waves cause the 4-km perpendicular arms of the interferometers to change length by miniscule (but different) amounts, the difference detected by changes in the resulting interference pattern as travel back and forth in the detector’s arms.

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You’ve seen a ton of videos of humanoid robots – but this one feels different. It’s Sanctuary’s Phoenix bot, with “the world’s best robot hands,” working totally autonomously at near-human speeds – much faster than Tesla’s or Figure’s robots.

Canadian company Sanctuary AI has been accelerating its own progress toward general-purpose humanoids, using teleoperation to show Phoenix how to do things, and letting it go away and figure out more in simulation.

Phoenix is an odd duck in this space, in that the Sanctuary team hasn’t got it up and walking yet, deciding to let others figure that bit out so its team can focus on the nitty gritty of work behaviors. Thus, it sits on a decidedly unsexy wheeled platform, but it has some of the most finely-tuned and human-like hands out of anything we’ve ever seen.

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