A logarithmic-depth quantum carry-lookahead adder

We present an efficient addition circuit, borrowing techniques from the classical carry-lookahead arithmetic circuit. Our quantum carry-lookahead (QCLA) adder accepts two n-bit numbers and adds them in O(log n) depth using O(n) ancillary qubits. We present both in-place and out-of-place versions, as well as versions that add modulo 2^n and modulo 2^n - 1. Previously, the linear-depth ripple-carry addition circuit has been the method of choice. Our work reduces the cost of addition dramatically with only a slight increase in the number of required qubits. The QCLA adder can be used within current modular multiplication circuits to reduce substantially the run-time of Shor's algorithm.Comment: 21 pages, 4 color figure

Identification of Fe3+-Li+ complexes in ZnO by means of high-frequency EPR/ENDOR spectroscopy

Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Fe, and other transition metals has stimulated the investigation of these materials by many research groups. Although charge-compensated Fe3+ centers in ZnO:Fe have been observed by means of EPR and have been known for decades, conclusions on the chemical nature of these defects are still contradictory. Originally, these centers were treated as Fe3+-Li + complexes with both ions occupying adjacent cationic sites. Recently, however, the centers were interpreted as a substitutional Fe 3+ ion with a vacancy at an adjacent zinc or oxygen site (Fe-V Zn or Fe-VO). In order to determine the chemical nature of the impurity associated with Fe3+, electron-nuclear double resonance (ENDOR) spectroscopy was used. ENDOR measurements reveal NMR transitions corresponding to nuclei with g-factor gN = 2.171 and spin I = 3/2. This unambiguously shows presence of Li as a charge compensator and also resolves contradictions with the theoretical prediction of the Fe-VO formation energy. The electric field gradients at the 7Li nuclei (within the Fe3+-Li+ complexes) were estimated to be significantly lower than the gradient at undistorted Zn sites. © 2013 Elsevier Inc. All rights reserved

Effect of quantum confinement and influence of extra charge on the electric field gradient in ZnO

By means of electron-nuclear double resonance (ENDOR), it is shown that the Al impurity, which acts as a shallow donor in ZnO, leads to a significant reduction of the electric field gradient in ZnO single crystals. In ZnO quantum dots, however, the gradient on the Al sites remains virtually unchanged. When the Zn 2+ ion is substituted by Mn 2+ in a ZnO single crystal, the electric field gradient slightly increases (by about 20%). Therefore, the Mn 2+ ions can be used as probes to monitor the electric field gradients in ZnO crystals. © 2012 Pleiades Publishing, Ltd

Synthesis and Optimization of Reversible Circuits - A Survey

Reversible logic circuits have been historically motivated by theoretical research in low-power electronics as well as practical improvement of bit-manipulation transforms in cryptography and computer graphics. Recently, reversible circuits have attracted interest as components of quantum algorithms, as well as in photonic and nano-computing technologies where some switching devices offer no signal gain. Research in generating reversible logic distinguishes between circuit synthesis, post-synthesis optimization, and technology mapping. In this survey, we review algorithmic paradigms --- search-based, cycle-based, transformation-based, and BDD-based --- as well as specific algorithms for reversible synthesis, both exact and heuristic. We conclude the survey by outlining key open challenges in synthesis of reversible and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table

Simulating chemistry efficiently on fault-tolerant quantum computers

Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain. Here we consider methods to make proposed chemical simulation algorithms computationally fast on fault-tolerant quantum computers in the circuit model. Fault tolerance constrains the choice of available gates, so that arbitrary gates required for a simulation algorithm must be constructed from sequences of fundamental operations. We examine techniques for constructing arbitrary gates which perform substantially faster than circuits based on the conventional Solovay-Kitaev algorithm [C.M. Dawson and M.A. Nielsen, \emph{Quantum Inf. Comput.}, \textbf{6}:81, 2006]. For a given approximation error $\epsilon$, arbitrary single-qubit gates can be produced fault-tolerantly and using a limited set of gates in time which is $O(\log \epsilon)$ or $O(\log \log \epsilon)$; with sufficient parallel preparation of ancillas, constant average depth is possible using a method we call programmable ancilla rotations. Moreover, we construct and analyze efficient implementations of first- and second-quantized simulation algorithms using the fault-tolerant arbitrary gates and other techniques, such as implementing various subroutines in constant time. A specific example we analyze is the ground-state energy calculation for Lithium hydride.Comment: 33 pages, 18 figure

Identification of shallow Al donors in ZnO

A combined magnetic resonance, photoluminescence, photoconductivity, and Raman scattering study of ZnO is presented. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy identify substitutional Al as a binding core of a shallow, effective-mass-like donor in ZnO. Based on the correlation between the EPR and photoluminescence data it is shown that recombination of an exciton bound to Al gives rise to the 3360.7meV photoluminescence line (I 6). A 1s→ 2p donor transition at 316cm -1 is detected in photoconductivity and Raman spectra. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The state of erection in a patient with craniopharyngioma, panhypopituitarism and diencephalic obesity

The article presents a clinical case from the practice of a patient with craniopharyngioma. The man of reproductive age with diencephalic obesity (BMI 35 kg/m2), recurrent craniopharyngioma, a long history of endocrine disorders (panhypopituitarism, including secondary hypogonadism, with the corresponding sexual function disorders and the lack of sexual activity), with visual disorders and psychiatric symptoms in the early postoperative period after shunting surgery and reducing the volume of the craniopharyngioma cyst, erection conditions arose against the background of episodes of disorders of consciousness within the framework of sleep dissociation. After the operation (installation of the Ommaya system), the patient had a state of «spontaneous» erection lasting up to 30 minutes against the background of dream-oneiric states of impaired consciousness with erotic experiences. These states were observed for 3 nights, the patient remembered the experiences and events that occurred to him «in a dream», and could tell about them to others on the next morning. The identity of the patient remained intact, he was active in the department, ordered in behavior; memory for current events and new information was intact. These disorders in the patient did not require specialized treatment, regressed independently on the 6th day of the postoperative period

Unilateral cross bite treated by corticotomy-assisted expansion: two case reports

<p>Abstract</p> <p>Background</p> <p>True unilateral posterior crossbite in adults is a challenging malocclusion to treat. Conventional expansion methods are expected to have some shortcomings. The aim of this paper is to introduce a new technique for treating unilateral posterior crossbite in adults, namely, corticotomy-assisted expansion (CAE) applied on two adult patients: one with a true unilateral crossbite and the other with an asymmetrical bilateral crossbite, both treated via modified corticotomy techniques and fixed orthodontic appliances.</p> <p>Methods</p> <p>Two cases with asymmetric maxillary constriction were treated using CAE.</p> <p>Results</p> <p>In both cases, effective asymmetrical expansion was achieved using CAE, and functional occlusion was established as well.</p> <p>Conclusions</p> <p>Unilateral CAE presents an effective and reliable technique to treat true unilateral crossbite.</p