Challenges in the use of quantum computing hardware-efficient Ansatze in electronic structure theory

Advances in quantum computation for electronic structure, and particularly heuristic quantum algorithms, create an ongoing need to characterize the performance and limitations of these methods. Here we discuss some potential pitfalls connected with the use of hardware-efficient Ansatze in variational quantum simulations of electronic structure. We illustrate that hardware-efficient Ansatze may break Hamiltonian symmetries and yield non-differentiable potential energy curves, in addition to the well-known difficulty of optimizing variational parameters. We discuss the interplay between these limitations by carrying out a comparative analysis of hardware-efficient Ansatze versus unitary coupled cluster and full configuration interaction, and of second- and first-quantization strategies to encode fermionic degrees of freedom to qubits. Our analysis should be useful in understanding potential limitations and in identifying possible areas of improvement in hardware-efficient Ansatze.Comment: 16 pages, 9 figures, supplemental information included as an ancillary fil

Two-years surveillance of fungal contamination in three hospital departments in Campania Region

A two-years (2003-2005) fungal environmental surveillance was carried out in three departments of a hospital in Campania region (Surgery, Intensive Care Unit, Obstetrics and Gynaecology). Four operating theatres rooms and their relative areas of service and support, 4 patient rooms of intensive care unit, 1 delivery room, 1 labour room and 1 nursery of Obstetrics and Gynaecology were checked. Atotal of 12,120 surfaces and 2,904 air samples were collected in 24 monthly determinations. A seasonal variation in the fungal development was observed, in particular the lowest level of air and surface fungi contamination was found in winter and autumn whereas it was higher in spring and summer. In this study 30 fungal species were identified and, among these, the most frequent specie isolated was the Aspergillus spp. The results show an air contamination, expressed in percentage of positive determinations for Aspergillus spp, and the other fungi in the following percentages: Obstetrics and Gynaecology (25% and 33,3%); Intensive Care Unit (17% and 25%); Surgery (12.5% and 21%). For surfaces contamination it was found: Obstetrics and Gynaecology (67% and 75%); Intensive Care Unit (63% and 71%); Surgery (58.3% and 67%). This study shows that in the departments observed environmental fungi contamination is always present and therefore it would be necessary to apply environmental surveillance procedure and monitor the effectiveness

Adverse health effects of nighttime lighting: comments on american medical association policy statement.

The American Medical Association House of Delegates in June of 2012 adopted a policy statement on nighttime lighting and human health. This major policy statement summarizes the scientific evidence that nighttime electric light can disrupt circadian rhythms in humans and documents the rapidly advancing understanding from basic science of how disruption of circadian rhythmicity affects aspects of physiology with direct links to human health, such as cell cycle regulation, DNA damage response, and metabolism. The human evidence is also accumulating, with the strongest epidemiologic support for a link of circadian disruption from light at night to breast cancer. There are practical implications of the basic and epidemiologic science in the form of advancing lighting technologies that better accommodate human circadian rhythmicity

Surveillance of nosocomial infections: a preliminary study on hand hygiene compliance of healthcare workers

The observance of hand hygiene compliance is important to reduce cross-infection by micro-organisms. The aim of this preliminary study was to evaluate the level of hand hygiene in healthcare workers from different departments, with particular emphasis on transient flora. The study was conducted in three departments (Surgery, Intensive Care Unit, Obstetrics and Gynecology) of a hospital in Campania, southern Italy. Over a six-month period, 50 healthcareworkers wererandomly tested. Imprints of palms and fingertips were taken monthly during the morning shift. The number of colonies per plate was counted and transient pathogens were identified. Risk factors for hand contamination were determined. Total flora was found in the following CFU means per palm and per five fingertips (95% CI): Obstetrics and Gynecology [palms 130 CFUs (95% CI 85-180); fingertips 125 CFUs (95% CI 92-160)]; ICU [palms 80 CFUs (95% CI 58-99); fingertips 62 CFUs (95% CI 45-82)]; Surgery [palms 75 CFUs (95% CI 41-120); fingertips 70 CFUs (95% CI 52-90)] Transient flora was found on 39% of healthcare workers?hands. The only factor associated with hand contamination by transient flora was the absence of gloving during healthcare procedure(P=0.02)

Quantum chemistry simulation of ground- and excited-state properties of the sulfonium cation on a superconducting quantum processor

The computational description of correlated electronic structure, and particularly of excited states of many-electron systems, is an anticipated application for quantum devices. An important ramification is to determine the dominant molecular fragmentation pathways in photo-dissociation experiments of light-sensitive compounds, like sulfonium-based photo-acid generators used in photolithography. Here we simulate the static and dynamical electronic structure of the H$_3$S$^+$ molecule, taken as a minimal model of a triply-bonded sulfur cation, on a superconducting quantum processor of the IBM Falcon architecture. To this end, we combine a qubit reduction technique with variational and diagonalization quantum algorithms, and use a sequence of error-mitigation techniques. We compute dipole structure factors and partial atomic charges along ground- and excited-state potential energy curves, revealing the occurrence of homo- and heterolytic fragmentation. To the best of our knowledge, this is the first simulation of a photo-dissociation reaction on a superconducting quantum device, and an important step towards the computational description of photo-dissociation by quantum computing algorithms.Comment: 12 pages, 7 figure

Subspace methods for electronic structure simulations on quantum computers

Quantum subspace methods (QSMs) are a class of quantum computing algorithms where the time-independent Schrodinger equation for a quantum system is projected onto a subspace of the underlying Hilbert space. This projection transforms the Schrodinger equation into an eigenvalue problem determined by measurements carried out on a quantum device. The eigenvalue problem is then solved on a classical computer, yielding approximations to ground- and excited-state energies and wavefunctions. QSMs are examples of hybrid quantum-classical methods, where a quantum device supported by classical computational resources is employed to tackle a problem. QSMs are rapidly gaining traction as a strategy to simulate electronic wavefunctions on quantum computers, and thus their design, development, and application is a key research field at the interface between quantum computation and electronic structure. In this review, we provide a self-contained introduction to QSMs, with emphasis on their application to the electronic structure of molecules. We present the theoretical foundations and applications of QSMs, and we discuss their implementation on quantum hardware, illustrating the impact of noise on their performance.Comment: 34 pages, 11 figure

NADP+-dependent dehydrogenase activity of carbonyl reductase on glutathionylhydroxynonanal as a new pathway for hydroxynonenal detoxification.

A NADP+ dependent dehydrogenase activity on 3-glutathionyl-4-hydroxynonanal (GSHNE) was purified to electrophoretic homogeneity from a line of human astrocytoma cells (ADF). Proteomic analysis identified this enzymatic activity as associated with carbonyl reductase 1 (E.C. 1.1.1.184). The enzyme is highly efficient at catalyzing the oxidation of GSHNE (KM33 µM,kcat.405 min-1), as it is practically inactive towards trans-4-hydroxy-2-nonenal (HNE) and other HNE-addicted thiol-containing amino acid derivatives. Combined mass spectrometry and nuclear magnetic resonance spectroscopy analysis of the reaction products revealed that carbonyl reductase oxidizes the hydroxyl group of GSHNE in its hemiacetal form, with the formation of the corresponding 3-glutathionyl-nonanoic-δ-lactone. The relevance of this new reaction catalyzed by carbonyl reductase 1 is discussed in terms of HNE detoxification and the recovery of reducing power

Resonant Lifetime of Core-Excited Organic Adsorbates from First Principles

We investigate by first-principles simulations the resonant electron-transfer lifetime from the excited state of an organic adsorbate to a semiconductor surface, namely isonicotinic acid on rutile TiO$_2$(110). The molecule-substrate interaction is described using density functional theory, while the effect of a truly semi-infinite substrate is taken into account by Green's function techniques. Excitonic effects due to the presence of core-excited atoms in the molecule are shown to be instrumental to understand the electron-transfer times measured using the so-called core-hole-clock technique. In particular, for the isonicotinic acid on TiO$_2$(110), we find that the charge injection from the LUMO is quenched since this state lies within the substrate band gap. We compute the resonant charge-transfer times from LUMO+1 and LUMO+2, and systematically investigate the dependence of the elastic lifetimes of these states on the alignment among adsorbate and substrate states.Comment: 24 pages, 6 figures, to appear in Journal of Physical Chemistry

Towards the solution of the many-electron problem in real materials: Equation of state of the hydrogen chain with state-of-the-art many-body methods

We present numerical results for the equation of state of an infinite chain of hydrogen atoms. A variety of modern many-body methods are employed, with exhaustive cross-checks and validation. Approaches for reaching the continuous space limit and the thermodynamic limit are investigated, proposed, and tested. The detailed comparisons provide a benchmark for assessing the current state of the art in many-body computation, and for the development of new methods. The ground-state energy per atom in the linear chain is accurately determined versus bond length, with a confidence bound given on all uncertainties