Demonstration of Algorithmic Quantum Speedup.

Despite the development of increasingly capable quantum computers, an experimental demonstration of a provable algorithmic quantum speedup employing today's non-fault-tolerant devices has remained elusive. Here, we unequivocally demonstrate such a speedup within the oracular model, quantified in terms of the scaling with the problem size of the time-to-solution metric. We implement the single-shot Bernstein-Vazirani algorithm, which solves the problem of identifying a hidden bitstring that changes after every oracle query, using two different 27-qubit IBM Quantum superconducting processors. The speedup is observed on only one of the two processors when the quantum computation is protected by dynamical decoupling but not without it. The quantum speedup reported here does not rely on any additional assumptions or complexity-theoretic conjectures and solves a bona fide computational problem in the setting of a game with an oracle and a verifier.

Sinusitis among Patients Undergoing CT Scan of Paranasal Sinuses in a Tertiary Care Centre: A Descriptive Cross-sectional Study.

Introduction: Computed tomography imaging provides detailed information about the paranasal sinuses and is now well established as an alternative to standard radiographs in evaluating patients with sinusitis. Sinusitis can have dangerous complications which can even lead to death if not diagnosed and treated on time. This study aimed to find the prevalence of sinusitis among the patients undergoing Computed Tomography scan of paranasal sinuses in a tertiary care centre. Methods: A descriptive cross-sectional study was conducted in the Department of Radiology at a tertiary care hospital from 1 October 2021 to 30 April 2022 after taking ethical approval from the Institutional Review Committee (Reference Number: 023-078/079). The patients undergoing Computed Tomography paranasal sinuses and meeting the eligibility criteria were enrolled for the study after taking informed consent. Convenience sampling was done. Point estimate and 95% Confidence Interval were calculated. Results: Among 113 patients, 109 (96.46%) (93.05-99.87, 95% Confidence Interval) patients had sinusitis. The most common subtype was found to be acute sinusitis in 63 (57.79%) individuals. Conclusions: The prevalence of sinusitis was higher than in other studies done in similar settings. Keywords: computed tomography; paranasal sinuses; sinusitis.

Chaos in the quantum Duffing oscillator in the semiclassical regime under parametrized dissipation.

We study the quantum dissipative Duffing oscillator across a range of system sizes and environmental couplings under varying semiclassical approximations. Using spatial complexity metrics based on Kullback-Leibler distances between phase-space attractors and temporal complexity metrics based on the Lyapunov exponent, we isolate the effect of the environment on quantum-classical differences. Moreover, we quantify the system sizes where quantum dynamics cannot be simulated using semiclassical or noise-added classical approximations. We find that a remarkable parametrically invariant meta-attractor emerges at a specific length scale and noise-added classical models deviate strongly from quantum dynamics below this scale. We also generalize the previous surprising result that classically regular orbits can have the greatest quantum-classical differences in the semiclassical regime and show that the dynamical growth of quantum-classical differences is not determined by the degree of classical chaos.

Demonstration of Fidelity Improvement Using Dynamical Decoupling with Superconducting Qubits.

Quantum computers must be able to function in the presence of decoherence. The simplest strategy for decoherence reduction is dynamical decoupling (DD), which requires no encoding overhead and works by converting quantum gates into decoupling pulses. Here, using the IBM and Rigetti platforms, we demonstrate that the DD method is suitable for implementation in today's relatively noisy and small-scale cloud-based quantum computers. Using DD, we achieve substantial fidelity gains relative to unprotected, free evolution of individual superconducting transmon qubits. To a lesser degree, DD is also capable of protecting entangled two-qubit states. We show that dephasing and spontaneous emission errors are dominant in these systems, and that different DD sequences are capable of mitigating both effects. Unlike previous work demonstrating the use of quantum error correcting codes on the same platforms, we make no use of postselection and hence report unconditional fidelity improvements against natural decoherence.

Chaos and dynamical complexity in the quantum to classical transition.

We study the largest Lyapunov exponents λ and dynamical complexity for an open quantum driven double-well oscillator, mapping its dependence on coupling to the environment Γ as well as effective Planck's constant ß2. We show that in general λ increases with effective Hilbert space size (as ß decreases, or the system becomes larger and closer to the classical limit). However, if the classical limit is regular, there is always a quantum system with λ greater than the classical λ, with several examples where the quantum system is chaotic even though the classical system is regular. While the quantum chaotic attractors are generally of the same family as the classical attractors, we also find quantum attractors with no classical counterpart. Contrary to the standard wisdom, the correspondence limit can thus be the most difficult to achieve for certain classically chaotic systems. These phenomena occur in experimentally accessible regimes.