Evidence of topological superconductivity in planar Josephson junctions.

Majorana zero modes-quasiparticle states localized at the boundaries of topological superconductors-are expected to be ideal building blocks for fault-tolerant quantum computing1,2. Several observations of zero-bias conductance peaks measured by tunnelling spectroscopy above a critical magnetic field have been reported as experimental indications of Majorana zero modes in superconductor-semiconductor nanowires3-8. On the other hand, two-dimensional systems offer the alternative approach of confining Majorana channels within planar Josephson junctions, in which the phase difference φ between the superconducting leads represents an additional tuning knob that is predicted to drive the system into the topological phase at lower magnetic fields than for a system without phase bias9,10. Here we report the observation of phase-dependent zero-bias conductance peaks measured by tunnelling spectroscopy at the end of Josephson junctions realized on a heterostructure consisting of aluminium on indium arsenide. Biasing the junction to φ ≈ π reduces the critical field at which the zero-bias peak appears, with respect to φ = 0. The phase and magnetic-field dependence of the zero-energy states is consistent with a model of Majorana zero modes in finite-size Josephson junctions. As well as providing experimental evidence of phase-tuned topological superconductivity, our devices are compatible with superconducting quantum electrodynamics architectures11 and are scalable to the complex geometries needed for topological quantum computing9,12,13.

Non-motor symptoms in early Parkinson's disease with different motor subtypes and their associations with quality of life.

BACKGROUND AND PURPOSE: The aim of this study was to examine non-motor symptoms in different Parkinson's disease (PD) motor subtypes and their associations with quality of life (QoL). METHODS: A total of 132 patients with early PD with comprehensive motor examinations and non-motor symptom assessments were included. Motor subtypes were classified based on Stebbins' method. Non-motor symptoms were assessed by the Non-Motor Symptom Scale (NMSS) and validated by more comprehensive instruments, including the Pittsburgh Sleep Quality Index (PSQI) and Fatigue Severity Scale (FSS). QoL was measured by the Parkinson's Disease Questionnaire-8. RESULTS: We identified 66 patients (50%) with tremor-dominant (TD) subtype, 47 (35.6%) with postural instability and gait disorder (PIGD) subtype and 19 (14.4%) with Intermediate subtype. By comparing NMSS scores, patients with the PIGD subtype had more severe sleep impairment and fatigue (domain 2 score: 5.64 vs. 2.52, P < 0.001), urinary symptoms (domain 7 score: 6.96 vs. 3.48, P = 0.005) and overall more severe non-motor symptoms (NMSS total score: 25.89 vs. 17.27, P = 0.031), compared with patients with the TD subtype. Validation using the PSQI and FSS again suggested that patients with the PIGD subtype had independently and significantly more severe sleep impairment (PSQI score: 5.57 vs. 4.29, P = 0.020) and fatigue (FSS score: 34.81 vs. 25.85, P = 0.003) compared with patients with the TD subtype. Several non-motor symptoms had significant associations with QoL, among which sleep impairment and fatigue (P < 0.0001, partial r2 = 0.273) explained the largest proportion of QoL variability in patients with PD. CONCLUSIONS: Patients with the PIGD subtype had more severe sleep impairment, fatigue and urinary disturbance compared with patients with the TD subtype. Sleep impairment and fatigue were the most important factors affecting QoL independent of motor subtypes. Prompt identification and treatment of these non-motor symptoms may improve patients' QoL.

Dynamical Detection of Topological Phase Transitions in Short-Lived Atomic Systems.

We demonstrate that dynamical probes provide direct means of detecting the topological phase transition (TPT) between conventional and topological phases, which would otherwise be difficult to access because of loss or heating processes. We propose to avoid such heating by rapidly quenching in and out of the short-lived topological phase across the transition that supports gapless excitations. Following the quench, the distribution of excitations in the final conventional phase carries signatures of the TPT. We apply this strategy to study the TPT into a Majorana-carrying topological phase predicted in one-dimensional spin-orbit-coupled Fermi gases with attractive interactions. The resulting spin-resolved momentum distribution, computed by self-consistently solving the time-dependent Bogoliubov-de Gennes equations, exhibits Kibble-Zurek scaling and Stückelberg oscillations characteristic of the TPT. We discuss parameter regimes where the TPT is experimentally accessible.