Lifeboat Foundation

We study the competing effects of collective generalized measurements and interaction-induced scrambling in the dynamics of an ensemble of spin-1/2 particles at the level of quantum trajectories. This setup can be considered as analogous to the one leading to measurement-induced transitions in quantum circuits. We show that the interplay between collective unitary dynamics and measurements leads to three regimes of the average Quantum Fisher Information (QFI), which is a witness of multipartite entanglement, as a function of the monitoring strength. While both weak and strong measurements lead to extensive QFI density (i.e., individual quantum trajectories yield states displaying Heisenberg scaling), an intermediate regime of classical-like states emerges for all system sizes where the measurement effectively competes with the scrambling dynamics and precludes the development of quantum correlations, leading to sub-Heisenberg-limited states. We characterize these regimes and the crossovers between them using numerical and analytical tools, and discuss the connections between our findings, entanglement phases in monitored many-body systems, and the quantum-to-classical transition.

While interactions within a many-body quantum system tend to generate highly correlated states, performing local measurements will typically tend to disentangle the different subsystems. When combined, the interplay between these two effects often lead to measurement-induced transitions, which separate two distinct stable phases: one interaction-driven, where entanglement is high, and another measurement-driven, where entanglement is low. However, different types of measurements can lead to other scenarios, and often also generate entanglement themselves. In this work we study quantum many-body systems where both interactions and measurements take place collectively and thus generate a high degree of entanglement if acting separately. We show that nontrivial competition between these two actors emerges, leading to configurations with very low entanglement.

In a recent study, a team of researchers at Max Planck Institute for Physics proposed that advanced extraterrestrial civilizations may be using black holes as quantum computers. No matter how advanced a civilization may be, we are all bound by the laws of quantum physics and gravity. So, if aliens are indeed out there, they could be using the geometry of spacetime around a black hole which behaves like a quantum computer. And, as if that weren’t enough, quantum computing is also immune to decryption, making it the perfect tool for secure communication. Roger Penrose, famously proposed that it is possible to extract limitless energy from a black hole by tapping into its Ergosphere. This is a region just outside the event horizon, where matter falling into the black hole forms a disk that spins at nearly the speed of light and emits massive amounts of radiation. Several researchers now suggest that this may be the ultimate power source for advanced civilizations. Subscribe to Science Time: https://www.youtube.com/sciencetime24 #science #shorts #space

Cosmologists believe that multiple universes really exist; they call the whole vast collection, which might even be infinite in number, the ‘multiverse’. But how are all these universes generated? There are several ways, each radically different from the others, each incredibly fascinating, each capable of generating infinite universes.

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In 1960, Luttinger proposed a universal principle connecting the total capacity of a system for particles with its response to low-energy excitations. Although easily confirmed in systems with independent particles, this theorem remains applicable in correlated quantum systems characterized by intense inter-particle interactions.

However, and quite surprisingly, Luttinger’s theorem has been shown to fail in very specific and exotic instances of strongly correlated phases of matter. The failure of Luttinger’s theorem and its consequences on the behavior of quantum matter are at the core of intense research in condensed matter physics.

An international collaboration, led by Macquarie University scientists, has introduced a new quantum optics technique that can provide unprecedented access to the fundamental properties of light-matter interactions in semiconductors.

The research, published Jan. 15 in the journal Nature Physics, uses a novel spectroscopic technique to explore interactions between photons and electrons at the quantum scale.

Professor Thomas Volz, co-author of the study and research group leader at Macquarie University’s School of Mathematical and Physical Sciences, says the work has the potential to drive a breakthrough in the global quest for accessible quantum photonic technologies.

The Hilbert space of a physical qubit typically features more than two energy levels. Using states outside the qubit subspace can provide advantages in quantum computation. To benefit from these advantages, individual states of the $d$-dimensional qudit Hilbert space have to be discriminated during readout. We propose and analyze two measurement strategies that improve the distinguishability of transmon qudit states. Based on a model describing the readout of a transmon qudit coupled to a resonator, we identify the regime in hardware parameter space where each strategy is optimal. We discuss these strategies in the context of a practical implementation of the default measurement of a ququart on IBM Quantum hardware whose states are prepared by employing higher-order $X$ gates that make use of two-photon transitions.

A significant breakthrough has been achieved by quantum physicists from Dresden and Würzburg. They’ve created a semiconductor device where exceptional robustness and sensitivity are ensured by a quantum phenomenon. This topological skin effect shields the functionality of the device from external perturbations, allowing for measurements of unprecedented precision.

This remarkable advance results from the clever arrangement of contacts on the aluminum-gallium-arsenide material. It unlocks potential for high-precision quantum modules in topological physics, bringing these materials into the semiconductor industry’s focus. These results, published in Nature Physics, mark a major milestone.

IBM warns that advancements in quantum computing could lead to a cybersecurity crisis.

Quasicrystals are intermetallic materials that have garnered significant attention from researchers aiming to advance condensed matter physics understanding. Unlike normal crystals, in which atoms are arranged in an ordered repeating pattern, quasicrystals have non-repeating ordered patterns of atoms.

Their unique structure leads to many exotic and interesting properties, which are particularly useful for practical applications in spintronics and magnetic refrigeration.

A unique quasicrystal variant, known as the Tsai-type icosahedral quasicrystal (iQC) and their cubic approximant crystals (ACs), display intriguing characteristics. These include long-range ferromagnetic (FM) and anti-ferromagnetic (AFM) orders, as well as unconventional quantum critical phenomenon, to name a few.