Natural orbitals and sparsity of quantum mutual information

Natural orbitals, defined in electronic structure and quantum chemistry as the (molecular) orbitals diagonalizing the one-particle reduced density matrix of the ground state, have been conjectured for decades to be the perfect reference orbitals to describe electron correlation. In the present work we applied the Wavefunction-Adapted Hamiltonian Through Orbital Rotation (WAHTOR) method to study correlated empirical ans\"atze for quantum computing. In all representative molecules considered, we show that the converged orbitals are coinciding with natural orbitals. Interestingly, the resulting quantum mutual information matrix built on such orbitals is also maximally sparse, providing a clear picture that such orbital choice is indeed able to provide the optimal basis to describe electron correlation. The correlation is therefore encoded in a smaller number of qubit pairs contributing to the quantum mutual information matrix.Comment: 11 pages + supplementary meteria

Pulse variational quantum eigensolver on cross-resonance based hardware

State-of-the-art noisy digital quantum computers can only execute short-depth quantum circuits. Variational algorithms are a promising route to unlock the potential of noisy quantum computers since the depth of the corresponding circuits can be kept well below hardware-imposed limits. Typically, the variational parameters correspond to virtual $R_Z$ gate angles, implemented by phase changes of calibrated pulses. By encoding the variational parameters directly as hardware pulse amplitudes and durations we succeed in further shortening the pulse schedule and overall circuit duration. This decreases the impact of qubit decoherence and gate noise. As a demonstration, we apply our pulse-based variational algorithm to the calculation of the ground state of different hydrogen-based molecules (H$_2$, H$_3$ and H$_4$) using IBM cross-resonance-based hardware. We observe a reduction in schedule duration of up to $5\times$ compared to CNOT-based Ans\"atze, while also reducing the measured energy. In particular, we observe a sizable improvement of the minimal energy configuration of H$_3$ compared to a CNOT-based variational form. Finally, we discuss possible future developments including error mitigation schemes and schedule optimizations, which will enable further improvements of our approach paving the way towards the simulation of larger systems on noisy quantum devices

Parsing the intrinsic networks underlying attention: A resting state study

The attention system functionally modulates brain activity to exert control over thoughts, feelings and actions. Three distinct but mutually interacting components of attention have been hypothesized: alerting, which mediates the maintenance of a state of vigilance toward an upcoming stimulus; orienting, which supports the selection of sensory information, and executive control that is involved in detecting and resolving cognitive conflicts. The performance of tasks probing these components engages fronto-parietal and thalamic regions. Also, general attention has been associated with the activity of resting-state networks (RSNs), which are sets of brain regions with synchronous temporal fluctuations. Importantly, the association between the intrinsic brain activity of RSNs and the efficiency and integration of the specific attentional components remains largely unexplored. For this aim, we recruited twenty healthy volunteers who performed the Attention Network Test-Revised (ANT-R), assessing the alerting, orienting and executive control components as well as their interactions, and underwent resting-state functional magnetic resonance imaging. For each participant RSNs were estimated using double regression. The RSNs spanning across areas previously implicated in attentional processing were correlated with ANT-R scores using multiple regressions. Significant brain behavior correlations emerged between ANT-R scores and RSNs comprising the regions relevant for attentional processing, i.e., left and right prefronto-parietal (PFC-PC), dorsal attentional (DAN), salience (SN), and default mode (DMN) networks. The activity of PFC-PC networks was correlated with alerting in parietal and frontal regions, and with location conflict in the frontal regions. The DAN connectivity was correlated with flanker, location conflict, and their interaction in parietal regions. SN was associated with flanker by location and flanker by orienting interactions in the inferior frontal regions. Finally, the activity of the DMN was associated with flanker conflict in midline structures such as precuneus and anterior cingulate cortex and also in right angular gyrus. These results suggest that the brain is endowed with an intrinsic functional organization to support attention, not only in its global function, but also in its distinct component

Starting aripiprazole long-acting-once-a-month early in treatment: why, how and for whom? Expert consensus and practical recommendations by a panel of Italian clinicians

Introduction: Aripiprazole long acting once-monthly (AOM) is approved for the treatment of schizophrenia in adults. Despite recent evidence of AOM efficacy in the acute treatment of schizophrenia, it is recommended that AOM should be started once the acute symptoms are controlled and patients are stabilized. However, there currently are no definitive guidelines exactly describing when a patient is to be considered stabilized enough to start AOM and which the patients are for whom an early AOM start is to be preferred. Areas covered: A panel of Italian clinicians experienced with real world use of AOM met to discuss the scenarios where an early (i.e., immediately after controlling the acute symptoms) start of AOM may be suggested. Real life clinical experiences were shared and a consensus was reached. Expert opinion: There are cases when the risks/benefits ratio suggests to start AOM early, i.e. immediately after the acute symptoms have been stabilized, as opposed to starting it several days/weeks after the stabilization of acute symptoms. Clinical pearls, guidelines and opinions are provided

Which patients discontinue? Issues on Levodopa/carbidopa intestinal gel treatment: Italian multicentre survey of 905 patients with long-term follow-up

Objectives To report the results of a national survey aimed at quantifying the current level of diffusion of Levodopa/carbidopa intestinal gel (LCIG) in Italy. Methods Sixty Parkinson's Disease (PD) specialists in Italy were invited to complete a survey covering issues on clinical and practical aspects of LCIG therapy. Results Clinical features of 905 patients were collected retrospectively. The majority of centres reported the use of a multidisciplinary team, biochemistry testing, neurophysiological and neuropsychological tests before and after treatment, in addition to caregivers’ training and patient's follow as outpatients. Most centres (60%) used internal guidelines for patient selection. The overall rate of adverse events was 55.1%. Weight loss, chronic polyneuropathy and stoma infection were the most frequently reported. 40% of centres used replacement therapy with Vitamin B12 and Folic acid from the start of LCIG and continued this for the duration of treatment. The rate of discontinuation was of 25.7% overall, with 9.5% of cases occurring in the first year. The main causes of withdrawal were device-related complications, disease progression (comorbidity, severe dementia) and caregiver and/or patient dissatisfaction. Conclusions In Italy LCIG infusion is managed in a uniform manner at a clinical, practical and organizational level even though the selection criteria are not standardized through the country. The high percentage of patients remaining on treatment in the short- and long-term follow-up confirms effectiveness of treatment, careful follow-up, and appropriate patient and caregivers training