Japan’s ambitious moonshot to develop fault-tolerant computers by 2050 has a clear goal, but it remains uncertain which technology will win out.
Category: quantum physics – Page 298
Quantum Resurrection: High-Performance Niobium Superconducting Qubits
For years, niobium was considered an underperformer when it came to superconducting qubits. Now scientists supported by Q-NEXT have found a way to engineer a high-performing niobium-based qubit and so take advantage of niobium’s superior qualities.
When it comes to quantum technology, niobium is making a comeback.
For the past 15 years, niobium has been sitting on the bench after experiencing a few mediocre at-bats as a core qubit material.
Scientists create dancing nanoparticles to explore quantum limitations
Enhancing quantum features compensates for environmental losses, amplifying particle interactions, achieving entanglement at higher scales.
One of the oldest topics of contemporary science is where to draw the line between classical and quantum physics.
Abstract
The ability to engineer cavity-mediated interactions has emerged as a powerful tool for the generation of non-local correlations and the investigation of non-equilibrium phenomena in many-body systems. Levitated optomechanical systems have recently entered the multi-particle regime, with promise for using arrays of massive strongly coupled oscillators for exploring complex interacting systems and sensing. Here, by combining advances in multi-particle optical levitation and cavity-based quantum control, we demonstrate, for the first time, programmable cavity-mediated interactions between nanoparticles in a vacuum. The interaction is mediated by photons scattered by spatially separated particles in a cavity, resulting in strong coupling (Gzz/Ωz = 0.238 ± 0.005) that does not decay with distance within the cavity mode volume. We investigate the scaling of the interaction strength with cavity detuning and inter-particle separation and demonstrate the tunability of interactions between different mechanical modes. Our work paves the way towards exploring many-body effects in nanoparticle arrays with programmable cavity-mediated interactions, generating entanglement of motion, and using interacting particle arrays for optomechanical sensing.
New maser in a ‘shoebox’ promises portable precision
Researchers in Imperial College London’s Department of Materials have developed a new portable maser that can fit the size of a shoebox.
Imperial College London pioneered the discovery of room-temperature solid-state masers in 2012, highlighting their ability to amplify extremely faint electrical signals and demonstrate high-frequency stability. This was a significant discovery because microwave signals can pass through the Earth’s atmosphere more easily than other wavelengths of light. Additionally, microwaves have the capability to penetrate through the human body, a feat not achievable by lasers.
Masers have extensive applications in telecommunications systems—everything from mobile phone networks to satellite navigation systems. They also have a key role in advancing quantum computing and improving medical imaging techniques, like MRI machines. They are typically large, bulky, stationary equipment found only in research laboratories.
Limitations of Linear Cross-Entropy as a Measure for Quantum Advantage
Popular Summary.
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.
Scientists make nanoparticles dance to unravel quantum limits
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 quantum entanglement, 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 quantum systems operate can make them difficult to observe and study.
Scientists Develop a Technique to Protect a Quantum-era Metaverse
A team of Chinese scientists introduced a quantum communication technique that they say could help secure Web 3.0 against the formidable threat of quantum computing.
Their approach, called Long-Distance Free-Space Quantum Secure Direct Communication (LF QSDC), promises to improve data security by enabling encrypted direct messaging without the need for key exchange, a method traditionally vulnerable to quantum attacks.
They add the approach not only enhances security but also aligns with the decentralized ethos of Web 3.0, offering a robust defense in the rapidly evolving digital landscape.