Transversal Gates Research Articles

Gate field induced electronic current modulation in a single wall boron nitride nanotube: Molecular scale field effect transistor

We report a first-principles quantum transport study in a single wall boron nitride nanotube sandwiched between a pair of gold electrodes. The non-equilibrium Green’s function approach, in which the electric field effect is explicitly included within a many body framework, is used to calculate the channel current, I sd , in the presence of a transverse gate field, E g . The E g is found to have a profound effect on the electronic current between the source and drain – revealing transistor behavior. The significant modulation in electronic current (ON–OFF current ratio of ∼ 18 at V sd of 3 V) is attributed to the giant Stark shift caused by the gate field.

Ballistic current in metal-oxide-semiconductor field-effect transistors: The role of device topology

In this study we investigate the effect of device topology on the ballistic current in n-channel metal-oxide-semiconductor field-effect transistors. Comparison of the nanoscale planar and double-gate devices reveals that, down to a certain thickness of the double gate film, the ballistic current flowing in the double gate device is twice as large compared to its planar counterpart. On the other hand, further thinning of the film beyond this threshold is found to change noticeably the confinement and transport characteristics, which are strongly depending on the film material and the surface orientation. For double gate Ge and Si devices there exists a critical film thickness below which the transverse gate field is no longer effectively screened by the inversion layer electron gas and mutual inversion of the two gates is turned on. In the case of GaAs and other similar III–V compounds, a decrease in the film thickness may drastically change the occupation of the L-valleys and therefore amend the transport properties. The simulation results show that, in both cases, the ballistic current and the transconductance are considerably enhanced.

Gated armchair nanotube and metallic field effect

We propose a useful metallic field effect element based on the electric field control of armchair single-wall carbon nanotube. The electron conduction channels are enhanced by imposing a transverse gate voltage. Multiple Dirac points have been revealed theoretically by our density functional and tight binding calculations. Our electron transport results show that the performance of such unique transistors depends mainly on the diameter of nanotube exploited. The critical field strength required decreases rapidly with the tube diameter.

Subsystem stabilizer codes cannot have a universal set of transversal gates for even one encoded qudit

A long-standing open problem in fault-tolerant quantum computation has been to find a universal set of transversal gates. As shown by Zeng et al. (e-print arXiv:0706.1382), such a set does not exist for binary stabilizer codes. Here we generalize our work to show that for subsystem stabilizer codes in $d$-dimensional Hilbert space, such a universal set of transversal gates cannot exist for even one encoded qudit, for any dimension $d$, prime or nonprime. This result strongly supports the idea that other primitives, such as quantum teleportation, are necessary for universal fault-tolerant quantum computation, and may be an important factor for fault-tolerance noise thresholds.

Local unitary versus local Clifford equivalence of stabilizer and graph states

The equivalence of stabilizer states under local transformations is of fundamental interest in understanding properties and uses of entanglement. Two stabilizer states are equivalent under the usual stochastic local operations and classical communication criterion if and only if they are equivalent under local unitary (LU) operations. More surprisingly, under certain conditions, two LU equivalent stabilizer states are also equivalent under local Clifford (LC) operations, as was shown by Van den Nest et al. [Phys. Rev. \textbf{A71}, 062323]. Here, we broaden the class of stabilizer states for which LU equivalence implies LC equivalence ($LU\Leftrightarrow LC$) to include all stabilizer states represented by graphs with neither cycles of length 3 nor 4. To compare our result with Van den Nest et al.'s, we show that any stabilizer state of distance $\delta=2$ is beyond their criterion. We then further prove that $LU\Leftrightarrow LC$ holds for a more general class of stabilizer states of $\delta=2$. We also explicitly construct graphs representing $\delta>2$ stabilizer states which are beyond their criterion: we identify all 58 graphs with up to 11 vertices and construct graphs with $2^m-1$ ($m\geq 4$) vertices using quantum error correcting codes which have non-Clifford transversal gates.

Electrical Switching in π-Resonant 1D Intermolecular Channels

We studied the influence of π-orbital coupling in a 1D stack of 4,4‘-biphenyldithiol (BDT) on the resulting electronic and electrical properties of the assembly. The conduction and the field-switching properties of the BDT assembly are compared as the intermolecular distances are reduced to below 4 Å. The system in the regime of strong π-interactions shows large conductance modulations upon application of a transverse gate field. The switching mechanism involves a delocalized π-resonance, i.e., resonant tunneling in the intermolecular π- and π*-bands of the BDT assembly. The transmission is found to be significantly higher in the π*-resonance. This behavior is discussed in terms of the density of states distribution in the conducting states.

Comprehensive on-line RPLC-CZE-MS of peptides

Peptide standards and tryptic digests of ribonuclease B are separated by comprehensive two-dimensional reversed phase liquid chromatography (RPLC) and capillary zone electrophoresis (CZE) and detected on-line by electrospray mass spectrometry. The RPLC column is coupled to the CZE column by a transverse flow gating interface. A new rugged microelectrospray needle is described that combines high ionization efficiency, low flow rates, and a sheath flow. The result is a system combining the separation capabilities of both RPLC and CZE with on-line mass spectrometric detection, all in about 15 min.

Transverse flow gating interface for the coupling of microcolumn LC with CZE in a comprehensive two-dimensional system

Transverse flow gating interface for the coupling of microcolumn LC with CZE in a comprehensive two-dimensional system

Time resolved spectroscopy of picosecond laser pulses with the aid of optical Kerr effect photography

An extension of the transverse gating, focal plane, optical Kerr effect photographic technique has permitted the direct observation of a frequency sweep within single ≈ 10 psec duration 0.53 μ wavelength pulses derived from a mode-locked Nd: glass laser.

Generation of Picosecond Pulse Electron Beams

Picosecond pulse electron beams were generated by means of a transverse-type gate and a buncher. The 20 keV beam was deflected by a 1 GHz symmetrical reentrant cavity and chopped by a slit into several tens picosecond pulses. These pulses were bunched by a 4 GHz reentrant cavity. The pulsed beam was then deflected by the other 1 GHz x–y deflectors and finally reached the screen, where the pulse width was measured by comparing the lengths of two chopped arcs with that of the unchopped full circle. A minimum pulse width of 6 psec was recorded. It was observed that as the deflecting voltage of the transverse gate increases, the pulse width decreases at first, reaches a minimum, and then increases. This can be explained by the longitudinal velocity modulation due to the fringing field of the deflector. When the beam chopped by the transverse gate was injected to the longitudinal gate, the maximum phase compression ratio was less than 5; this is also explained by the above-mentioned effect.

Deep gates of a new design for closure of diversion tunnels

1. The discussed gate has a number of merits: the absence of deformation of the stream (except for deformation with a partial opening) ensures resistance to cavitation and vibration and increases the discharge coefficient; the action of the gate material only in compression or in tension makes it possible to reduce its weight substantially; the operation of the gate as a closed system which does not transfer its external loads to the foundation makes it possible to reduce the load on the gate 100–200 fold and to maneuver it with smaller mechanisms. The sharp reduction in load on the supporting bearings not only reduces their cost but above all, increases their dependability. 2. The indicated properties make it possible, depending on specific conditions, to build both the principal and the emergency-repair gates in three variants: concrete, thin-wall reinforced concrete, and metal. 3. The most dependable and economical emergency-repair gate for tunnels of large cross sections under high heads must be considered the one in the form of a concrete roll-away prism which subsequently becomes part of the concrete plug of the construction conduit; this makes it possible to allocate a considerable part of its cost to that of filling the tunnel. The high safety factor accounts for a number of advantages of this gate over other known types of emergency-repair gates. 4. The metal, transverse multi-pipe gate used as the principal gate has definite advantages; it is highly flexible and uses a small amount of metal. 5. The fact that the shape and dimensions of the conduit in the flow part of the gate chamber are not changed makes it possible to reduce sharply the expenditure of metal in lining and simultaneously to increase the operational dependability, thus achieving a marked savings.