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Category: quantum physics

Novel quantum dynamics with superconducting qubits

The prevailing view is that quantum phenomena can be leveraged to tackle certain problems beyond the reach of classical approaches. Recent years have witnessed significant progress in this direction; in particular, superconducting qubits have emerged as one of the leading platforms for quantum simulation and computation on Noisy Intermediate-Scale Quantum (NISQ) processors. This progress is exemplified by research ranging from the foundations of quantum mechanics to the non-equilibrium dynamics of elementary excitations and condensed matter physics.

By utilizing the contextuality of quantum measurements to solve a 2D hidden linear function problem, we demonstrate a quantum advantage through a computational separation for up to 105 qubits on these bounded-resource tasks. Motivated by high-energy physics, we image charge and string dynamics in (2+1)D lattice gauge theories, revealing two distinct regimes within the confining phase: a weak-confinement regime with strong transverse string fluctuations and a strong-confinement regime where these fluctuations are suppressed. Turning to condensed matter, we observe novel localization in one-and two-dimensional many-body systems that lack energy diffusion despite being disorder-free and translationally invariant. Additionally, we show that strong disorder in interacting multi-level landscapes can induce superfluidity characterized by long-range phase coherence.

Silicon quantum processor detects single-qubit errors while preserving entanglement

Quantum computers are alternative computing devices that process information, leveraging quantum mechanical effects, such as entanglement between different particles. Entanglement establishes a link between particles that allows them to share states in such a way that measuring one particle instantly affects the others, irrespective of the distance between them.

Quantum computers could, in principle, outperform classical computers in some optimization and computational tasks. However, they are also known to be highly sensitive to environmental disturbances (i.e., noise), which can cause quantum errors and adversely affect computations.

Researchers at the International Quantum Academy, Southern University of Science and Technology, and Hefei National Laboratory have developed a new approach to detect these errors in a silicon-based quantum processor. This error detection strategy, presented in a paper published in Nature Electronics, was found to successfully detect quantum errors in silicon qubits, while also preserving entanglement after their detection.

Using light to probe fractional charges in a fractional Chern insulator

In some quantum materials, which are materials governed by quantum mechanical effects, interactions between charged particles (i.e., electrons) can prompt the creation of quasiparticles called anyons, which carry only a fraction of an electron’s charge (i.e., fractional charge) and fractional quantum statistics.

A well-known phenomenon characterized by the emergence of anyons is the so-called fractional quantum Hall effect (FQHE). This effect can emerge in two-dimensional (2D) electron gases under strong magnetic fields and is marked by quantum states in which electrons strongly interact with each other.

Recent studies showed that a similar effect can also arise in the absence of magnetic fields, known as fractional quantum anomalous Hall (FQAH) effect, in quantum phases of matter fractional Chern insulators (FCIs). The FQAH effect was realized for the first time using bilayer twisted molybdenum ditelluride (tMoTe₂)—a moiré superlattice that has a characteristic lattice pattern and a slight twist angle between constituent layers.

Optical switch protocol verifies entangled quantum states in real time without destroying them

The fragility and laws of quantum physics generally make the characterization of quantum systems time‑consuming. Furthermore, when a quantum system is measured, it is destroyed in the process. A breakthrough by researchers at the University of Vienna demonstrates a novel method for quantum state certification that efficiently verifies entangled quantum states in real time without destroying all available states—a decisive step forward in the development of robust quantum computers and quantum networks.

The work was carried out in Philip Walther’s laboratories at the Faculty of Physics and the Vienna Center for Quantum Science and Technology (VCQ) and published in the journal Science Advances.

Entangled quantum states are the fundamental building blocks of many new quantum technologies, from ultra‑secure communication to powerful quantum computing. However, before these delicate states can be used, they must be rigorously verified to ensure their quality and integrity.

Q-Day: Catastrophic For Businesses Ignoring Quantum-Resistant Encryption

#Quantum #CyberSecurity

Quantum computing is not merely a frontier of innovation; it is a countdown. Q-Day is the pivotal moment when scalable quantum computers undermine the cryptographic underpinnings of our digital realm. It is approaching more rapidly than many comprehend.

For corporations and governmental entities reliant on outdated encryption methods, Q-Day will not herald a smooth transition; it may signify a digital catastrophe.

Comprehending Q-Day: The Quantum Reckoning

Q-Day arrives when quantum machines using Shor’s algorithm can dismantle public-key encryption within minutes—a task that classical supercomputers would require billions of years to accomplish.

Strong correlations and superconductivity observed in a supermoiré lattice

Two or more graphene layers that are stacked with a small twist angle in relation to each other form a so-called moiré lattice. This characteristic pattern influences the movement of electrons inside materials, which can give rise to strongly correlated states, such as superconductivity.

Researchers at Ecole Polytechnique Fédérale de Lausanne, Freie Universität Berlin and other institutes recently uncovered a strong superconductivity in a supermoiré lattice, a twisted trilayer graphene structure with broken symmetry in which several moiré patterns overlap. Their paper, published in Nature Physics, could open new possibilities for the design of quantum materials for various applications.

“Fabricating a twisted trilayer graphene device with two distinct twist angles was not our original intention,” Mitali Banerjee, senior author of the paper, told Phys.org. “Instead, we aimed to make a device in which the two twist angles are identical in magnitude (magic-angle twisted trilayer). During our measurements, however, my student Zekang Zhou found that the phase diagram of this device differs fundamentally from that of magic-angle twisted trilayer graphene.”

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