Discrete Time-Crystalline Order Enabled by Quantum Many-Body Scars: Entanglement Steering via Periodic Driving.

The control of many-body quantum dynamics in complex systems is a key challenge in the quest to reliably produce and manipulate large-scale quantum entangled states. Recently, quench experiments in Rydberg atom arrays [Bluvstein et al. Science 371, 1355 (2021)SCIEAS0036-807510.1126/science.abg2530] demonstrated that coherent revivals associated with quantum many-body scars can be stabilized by periodic driving, generating stable subharmonic responses over a wide parameter regime. We analyze a simple, related model where these phenomena originate from spatiotemporal ordering in an effective Floquet unitary, corresponding to discrete time-crystalline behavior in a prethermal regime. Unlike conventional discrete time crystals, the subharmonic response exists only for Néel-like initial states, associated with quantum scars. We predict robustness to perturbations and identify emergent timescales that could be observed in future experiments. Our results suggest a route to controlling entanglement in interacting quantum systems by combining periodic driving with many-body scars.

Transition across polymorphic phenotypes observed in a male Sternarchogiton nattereri (Gymnotiformes: Apteronotidae).

A transition between polymorphic phenotypes was observed within a single male Sternarchogiton nattereri. This individual was initially toothless, but developed into a toothed phenotype characterized by a swollen distal upper jaw and distinctive external dentition. Changes in morphological features were accompanied by shifts in electrocommunication (chirping) behaviour.

Controlling quantum many-body dynamics in driven Rydberg atom arrays.

The control of nonequilibrium quantum dynamics in many-body systems is challenging because interactions typically lead to thermalization and a chaotic spreading throughout Hilbert space. We investigate nonequilibrium dynamics after rapid quenches in a many-body system composed of 3 to 200 strongly interacting qubits in one and two spatial dimensions. Using a programmable quantum simulator based on Rydberg atom arrays, we show that coherent revivals associated with so-called quantum many-body scars can be stabilized by periodic driving, which generates a robust subharmonic response akin to discrete time-crystalline order. We map Hilbert space dynamics, geometry dependence, phase diagrams, and system-size dependence of this emergent phenomenon, demonstrating new ways to steer complex dynamics in many-body systems and enabling potential applications in quantum information science.

Outcome analysis of intraventricular thrombolytic therapy for intraventricular haemorrhage.

OBJECTIVES: To evaluate the outcome of intraventricular thrombolytic therapy for intraventricular haemorrhage and to formulate a safe and effective regimen. DESIGN: Retrospective study. SETTING: Regional neurosurgical centre, Hong Kong. PATIENTS: Twenty-nine consecutive adult patients who presented from November 1995 to November 1998 with non-traumatic intraventricular haemorrhage (Graeb score, > or =7) with no active rebleeding risks from vascular abnormalities. INTERVENTIONS: Fourteen consecutive patients received intraventricular streptokinase via the external ventricular drainage, and 15 consecutive patients received intraventricular urokinase treatment. MAIN OUTCOME MEASURES: Patient demographics, Glasgow coma scale score, Graeb score, mortality rate, shunt rate, fever response, infection rate, catheter blockage rate, and local and systemic bleeding tendency. RESULT: The mean age of the 16 men and 13 women was 59 years (range, 14-76 years). The median Graeb score for cases of intraventricular haemorrhage was 10 (range, 7-12). There was no significant difference in terms of the Graeb score distribution, total dosage, and duration of treatment between the streptokinase and urokinase groups. More cases of fever were observed in the streptokinase group, which could be due to its antigenicity. The infection rate of the central nervous system was 3%, and the shunt rate was 24%. The overall 1-month postoperative mortality was 10%, which was related to a low preoperative Glasgow coma scale score (< or =4). No local rebleeding, systemic coagulopathy, or catheter blockage occurred. CONCLUSIONS: Intraventricular thrombolytic therapy is a safe and effective method of managing intraventricular haemorrhage. We suggest instilling 20 000 units urokinase intra-operatively, followed by 20 000 units daily for about 3 days, except in cases of vascular abnormality, bleeding tendency, and trauma.