Quantum Computation of Hydrogen Bond Dynamics and Vibrational Spectra.

Calculating observable properties of chemical systems is often classically intractable and widely viewed as a promising application of quantum information processing. Here, we introduce a new framework for solving generic quantum chemical dynamics problems using quantum logic. We experimentally demonstrate a proof-of-principle instance of our method using the QSCOUT ion-trap quantum computer, where we experimentally drive the ion-trap system to emulate the quantum wavepacket dynamics corresponding to the shared-proton within an anharmonic hydrogen bonded system. Following the experimental creation and propagation of the shared-proton wavepacket on the ion-trap, we extract measurement observables such as its time-dependent spatial projection and its characteristic vibrational frequencies to spectroscopic accuracy (3.3 cm-1 wavenumbers, corresponding to >99.9% fidelity). Our approach introduces a new paradigm for studying the chemical dynamics and vibrational spectra of molecules and opens the possibility to describe the behavior of complex molecular processes with unprecedented accuracy.

Truncated SALL1 Impedes Primary Cilia Function in Townes-Brocks Syndrome.

Townes-Brocks syndrome (TBS) is characterized by a spectrum of malformations in the digits, ears, and kidneys. These anomalies overlap those seen in a growing number of ciliopathies, which are genetic syndromes linked to defects in the formation or function of the primary cilia. TBS is caused by mutations in the gene encoding the transcriptional repressor SALL1 and is associated with the presence of a truncated protein that localizes to the cytoplasm. Here, we provide evidence that SALL1 mutations might cause TBS by means beyond its transcriptional capacity. By using proximity proteomics, we show that truncated SALL1 interacts with factors related to cilia function, including the negative regulators of ciliogenesis CCP110 and CEP97. This most likely contributes to more frequent cilia formation in TBS-derived fibroblasts, as well as in a CRISPR/Cas9-generated model cell line and in TBS-modeled mouse embryonic fibroblasts, than in wild-type controls. Furthermore, TBS-like cells show changes in cilia length and disassembly rates in combination with aberrant SHH signaling transduction. These findings support the hypothesis that aberrations in primary cilia and SHH signaling are contributing factors in TBS phenotypes, representing a paradigm shift in understanding TBS etiology. These results open possibilities for the treatment of TBS.

Genetic Analysis of 'PAX6-Negative' Individuals with Aniridia or Gillespie Syndrome.

We report molecular genetic analysis of 42 affected individuals referred with a diagnosis of aniridia who previously screened as negative for intragenic PAX6 mutations. Of these 42, the diagnoses were 31 individuals with aniridia and 11 individuals referred with a diagnosis of Gillespie syndrome (iris hypoplasia, ataxia and mild to moderate developmental delay). Array-based comparative genomic hybridization identified six whole gene deletions: four encompassing PAX6 and two encompassing FOXC1. Six deletions with plausible cis-regulatory effects were identified: five that were 3' (telomeric) to PAX6 and one within a gene desert 5' (telomeric) to PITX2. Sequence analysis of the FOXC1 and PITX2 coding regions identified two plausibly pathogenic de novo FOXC1 missense mutations (p.Pro79Thr and p.Leu101Pro). No intragenic mutations were detected in PITX2. FISH mapping in an individual with Gillespie-like syndrome with an apparently balanced X;11 reciprocal translocation revealed disruption of a gene at each breakpoint: ARHGAP6 on the X chromosome and PHF21A on chromosome 11. In the other individuals with Gillespie syndrome no mutations were identified in either of these genes, or in HCCS which lies close to the Xp breakpoint. Disruption of PHF21A has previously been implicated in the causation of intellectual disability (but not aniridia). Plausibly causative mutations were identified in 15 out of 42 individuals (12/32 aniridia; 3/11 Gillespie syndrome). Fourteen of these mutations presented in the known aniridia genes; PAX6, FOXC1 and PITX2. The large number of individuals in the cohort with no mutation identified suggests greater locus heterogeneity may exist in both isolated and syndromic aniridia than was previously appreciated.

Ultrafast optical control of orbital and spin dynamics in a solid-state defect.

Atom-scale defects in semiconductors are promising building blocks for quantum devices, but our understanding of their material-dependent electronic structure, optical interactions, and dissipation mechanisms is lacking. Using picosecond resonant pulses of light, we study the coherent orbital and spin dynamics of a single nitrogen-vacancy center in diamond over time scales spanning six orders of magnitude. We develop a time-domain quantum tomography technique to precisely map the defect's excited-state Hamiltonian and exploit the excited-state dynamics to control its ground-state spin with optical pulses alone. These techniques generalize to other optically addressable nanoscale spin systems and serve as powerful tools to characterize and control spin qubits for future applications in quantum technology.

All-optical control of a solid-state spin using coherent dark states.

The study of individual quantum systems in solids, for use as quantum bits (qubits) and probes of decoherence, requires protocols for their initialization, unitary manipulation, and readout. In many solid-state quantum systems, these operations rely on disparate techniques that can vary widely depending on the particular qubit structure. One such qubit, the nitrogen-vacancy (NV) center spin in diamond, can be initialized and read out through its special spin-selective intersystem crossing, while microwave electron spin resonance techniques provide unitary spin rotations. Instead, we demonstrate an alternative, fully optical approach to these control protocols in an NV center that does not rely on its intersystem crossing. By tuning an NV center to an excited-state spin anticrossing at cryogenic temperatures, we use coherent population trapping and stimulated Raman techniques to realize initialization, readout, and unitary manipulation of a single spin. Each of these techniques can be performed directly along any arbitrarily chosen quantum basis, removing the need for extra control steps to map the spin to and from a preferred basis. Combining these protocols, we perform measurements of the NV center's spin coherence, a demonstration of this full optical control. Consisting solely of optical pulses, these techniques enable control within a smaller footprint and within photonic networks. Likewise, this unified approach obviates the need for both electron spin resonance manipulation and spin addressability through the intersystem crossing. This method could therefore be applied to a wide range of potential solid-state qubits, including those which currently lack a means to be addressed.

Singleton-Merten syndrome: an autosomal dominant disorder with variable expression.

In 1973, Singleton and Merten described two females with abnormal dentition, unique radiographic changes especially of the hands, and severe calcification and intimal weakening of the aortic arch and valve. Since then three additional cases with similar features have been reported and the diagnosis was suggested in another three individuals. We present an update of one case and the detailed clinical phenotype of six other cases with Singleton-Merten syndrome. The occurrence of the disorder in six members of two families and vertical male-to-male transmission indicate an autosomal dominant pattern of inheritance. Variability in phenotype, also within a single family, is significant. Core manifestations are marked aortic calcification, dental anomalies (delayed eruption and immature root formation of primarily the anterior permanent teeth, and early loss of permanent teeth due to short roots, acute root resorption, high caries, and aggressive alveolar bone loss), osteopenia and acro-osteolysis, and to a lesser extend also glaucoma, psoriasis, muscle weakness, and joint laxity. Additional clinical characteristics described here include particular facial characteristics (high anterior hairline, broad forehead, smooth philtrum, thin upper vermillion) and abnormal joint and muscle ligaments. The cause and pathogenesis of this syndrome remain unknown. © 2013 Wiley Periodicals, Inc.

Homoepitaxial growth of single crystal diamond membranes for quantum information processing.

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.