Quantum Trap Research Articles

Quantum trapping and rotational self-alignment in triangular Casimir microcavities.

Casimir torque, a rotational motion driven by zero-point energy minimization, is a problem that attracts notable research interest. Recently, it has been realized using liquid crystal phases and natural anisotropic substrates. However, for natural materials, substantial torque occurs only at van der Waals distances of ~10 nm. Here, we use Casimir self-assembly with triangular gold nanostructures for rotational self-alignment at truly Casimir distances (100 to 200 nm separation). The interplay of repulsive electrostatic and attractive Casimir potentials forms a stable quantum trap, giving rise to a tunable Fabry-Pérot microcavity. This cavity self-aligns both laterally and rotationally to maximize area overlap between templated and floating flakes. The rotational self-alignment is sensitive to the equilibrium distance between the two triangles and their area, offering possibilities for active control via electrostatic screening manipulation. Our self-assembled Casimir microcavities present a versatile and tunable platform for nanophotonic, polaritonic, and optomechanical applications.

Physical Limit of Nonlinear Brownian Oscillators in Quantum Trap.

Quantum trap, a quantum and thermal fluctuations-induced nonmonotonous potential, offers a chance to build up microscopic mechanical systems completely dominated by fluctuations. Here, we explore the physical limit of the effective damping ratio of the nonlinear Brownian oscillator in a quantum trap, set by the finite separation for avoiding molecular-scale effects on the trap potential and the surface confinement effect-induced diverging damping and random forces. The quasiharmonic approximations and Langevin dynamics simulations show that the lowest effective damping ratios of the suspended Au plate and Au sphere upon a Teflon coating of 10 nm can be ∼210 and ∼145, respectively, at room temperature. Perforation is proposed as an effective route to reduce the damping ratio (down to 6.4) by attenuating the surface confinement effect. An unexpected result due to the temperature dependences of dielectric function and viscosity of ethanol is a further reduced damping ratio at 400 K (1.3). The nonlinear Brownian oscillator in the quantum trap shows promise of probing near-boundary hydrodynamics at nanoscale.

Large Casimir Flipping Torque in Quantum Trap.

Casimir torque between parallel plates, a macroscopic quantum electrodynamics effect, is known to be induced by dielectric anisotropy and related to the rotational degree of freedom. We here reveal a different type of Casimir torque generated on a Au plate suspended in a quantum trap without recourse to materials anisotropy. As the Au plate deflects from the equilibrium plane with a nonzero flipping angle, the regions departing from and approaching the Teflon-coated Au substrate are subjected to attractive and repulsive Casimir forces, respectively, resulting in a restoring torque about the axis of flipping. For a quantum trap with an equilibrium separation of ∼10 nm, the stiffness per unit area of the Casimir flipping torque can be an order of magnitude larger than those of previously reported dielectric anisotropy-induced rotational torques at the same separation. The large Casimir flipping torque provides the possibility of designing a mechanical oscillator completely dominated by quantum and thermal fluctuations.

Enhanced charge generation and transfer properties on anatase nanodendrite array photo-electrodes for high-efficiency quantum dot sensitized solar cells

The loading amount of quantum dots and trap density are the significant issues for quantum dot sensitized solar cells. Anatase TiO2 nanodendrite array is employed as the photo-electrodes for the CuInS2 quantum dot sensitized solar cells instead of the traditional TiO2 nanowire array, which is prepared by two-step hydrothermal process. The excellent charge generation and charge separation properties have been exhibited by the CuInS2 quantum dots sensitized photo-electrodes based on the anatase TiO2 nanodendrite array, which are characterized by the optical absorption spectra and photoluminescence spectra. Meanwhile, the branches from anatase TiO2 nanodendrite array provide much more paths for charge transfer and reduce the charge recombination traps in photo-electrodes, which have provided excellent charge transfer property for the solar cells. As a result, higher current density can be obtained by anatase TiO2 nanodendrite array structure based CuInS2 quantum dot sensitized solar cells, which has exhibited the photovoltaic conversion efficiency enhancement from 4.7% to 5.48%.

Multiple quantum interrogation to determine the position of an object in a serial array of ring resonators

We propose quantum interaction-free measurements to determine not only whether an object exists, but also where it is situated among possible interrogation positions. In the first configuration, the object exists at one of several possible positions, and the other positions are empty. We regard this as multiple quantum trap interrogation. In the second configuration, the object does not exist in any possible interrogation position, but other positions are occupied by objects. We refer to this as multiple quantum loophole interrogation. It is possible to determine the position of a trap or loophole with almost 100% certainty, without any real interaction between the photon and the objects. We performed a preliminary experiment using a serial array of add-drop ring resonators and confirmed that multiple trap and loophole interrogations are possible. We discuss the detuning of resonators from the critical coupling condition, the loss effects in the resonator, the frequency detuning effect of incident light, and the effect of object semitransparency on the interrogation systems.

RESEARCH OF QUANTUM KEY DISTRIBUTION PROTOCOLS: BB84, B92, E91

The proposed article is devoted to the investigation of quantum key distribution protocols. The idiosyncrasy of this theme lies within the truth that present day strategies of key distribution, which utilize classical computing at their center, have critical downsides, in contrast to quantum key distribution. This issue concerns all sorts of calculations and frameworks for scrambling mystery data, both symmetric encryption with a private key and deviated encryption with an open key. A case is that in a communication channel ensured by quantum key distribution, it is conceivable to distinguish an interceptor between two legitimate organize substances utilizing the standards laid down in quantum material science at the starting of the final century. Standards and hypotheses such as the Heisenberg guideline, quantum trap, superposition, quantum teleportation, and the no-cloning hypothesis. The field of ponder of this theme may be a promising and quickly creating zone within the field of data security and data security. There are as of now made commercial items with the usage of a few of the quantum key dispersion conventions. Numerous of the made items are utilized in different circles of human movement. The significance of applying quantum key distribution conventions beneath perfect conditions without taking into consideration blunders within the frame of quantum clamor is analyzed. The usage of three quantum key distribution conventions is illustrated, as well as the comes about of the appearance of keys and the likelihood of event of each of them. The purpose of the article is pointed at analyzing and investigating quantum key distribution conventions. The article examines the points of interest and impediments of the BB84, B92, and E91 quantum key distribution conventions.

On quantum evolving schemes

A quantum secret sharing scheme is a method to share a quantum secret among participants in such a way that only certain specified subsets of the set of participants can combine to recover the secret. A quantum evolving secret sharing scheme is a recently introduced variant of secret sharing schemes where the sets of participants is not fixed and an unbounded and unspecified number of participants arrive one by one with time. The number of participants can be potentially infinite and and a quantum secret is shared and protected among the participants. The existing construction has some major drawbacks such as 1) the exponential quantum memory requirement and 2) the very high dimensions of the shares which makes the scheme difficult to implement. In this paper we overcome these drawbacks by constructing a scheme which uses quantum memory linear in the number of participants and significantly improves on the dimensions of the shares of the participants. This construction uses quantum secret redistribution and trap codes. The construction is flexible and can be modified to different types of access structures(subsets of participants which can recover the secret). Certain ramp properties can also be incorporated in the scheme.

A study of photoelectric properties of grown SnSe2 crystal by direct vapour transport technique

The opto-electrical properties of Tin Diselenide (SnSe2) crystal are significant for application in photo detectors, optoelectronic devices and many more. Metal chalcogenide SnSe2 has been grown by direct vapor transport (DVT) technique. The chemical composition of grown crystal was studied by energy dispersive analysis of X-ray (EDAX). The photo detection property of SnSe2 crystal based photo detector was exploited for their envisioned applications in optoelectronics. SnSe2 crystals have observed an outstanding photo response ability at room temperature (300 K) with changing illumination intensities 50, 75, 100 and 125 mw/cm2. Moreover, the related parameters, photoresponsivity (R) spectral detectivity (D), external quantum efficiency (EQE), internal quantum efficiency (IQE) and trap depth parameters have been evaluated for pure SnSe2 crystal.

Bi-states and 2-level systems in rectangular Penning traps

We introduce a notion of semiclassical bi-states. They arise from pairs of eigenstates corresponding to tunnel-split eigenlevels and generate 2-level subsystems in a given quantum system. As an example, we consider the planar Penning trap with rectangular electrodes assuming the 3: (−1) resonance regime of the charge dynamics. We demonstrate that, under a small deviation of the rectangular shape of electrodes from the square shape (symmetry breaking), there appear instanton pseudoparticles, semiclassical bi-states, and 2-level subsystems in such a quantum trap.

Effect of Size and Dimensionality on the Band Gap and Conductivity of InAs, PbS, Ge, and Bi2S3 Nanostructured Semiconductors

The band gap and conductivity of a nano-semiconductor are tunable with the specimen size and dimensionality, and related mechanisms are under debating. From the perspective of bond orderlength- strength correlation, we have developed analytical expressions for investigating size- and dimensionality- induced change of the band gap, charge carrier concentration and conductivity of InAs, PbS, Ge, and Bi2S3 nano-semiconductor. Consistency in theoretical predictions, experimental observations, and numerical calculations clarified that size and dimensionality dependent these properties arise from surface strain and the associated quantum trap of binding energy. The surface-to-volume ratio is a key factor, which dominates size and dimensionality dependency. Keywords: Nano-semiconductors, quantum entrapment, surface strain, surface-to-volume ratio.

Conditions for order and chaos in the dynamics of a trapped Bose-Einstein condensate in coordinate and energy space

We investigate numerically conditions for order and chaos in the dynamics of an interacting Bose- Einstein condensate (BEC) confined by an external trap cut off by a hard-wall box potential. The BEC is stirred by a laser to induce excitations manifesting as irregular spatial and energy oscillations of the trapped cloud. Adding laser stirring to the external trap results in an effective time-varying trapping frequency in connection with the dynamically changing combined external+laser potential trap. The resulting dynamics are analyzed by plotting their trajectories in coordinate phase space and in energy space. The Lyapunov exponents are computed to confirm the existence of chaos in the latter space. Quantum effects and trap anharmonicity are demonstrated to generate chaos in energy space, thus confirming its presence and implicating either quantum effects or trap anharmonicity as its generator. The presence of chaos in energy space does not necessarily translate into chaos in coordinate space. In general, a dynamic trapping frequency is found to promote chaos in a trapped BEC. An apparent means to suppress chaos in a trapped BEC is achieved by increasing the characteristic scale of the external trap with respect to the condensate size.

Quantum-mechanical engines working with an ideal gas with a finite number of particles confined in a power-law trap

Based on quantum thermodynamic processes, we make a quantum-mechanical (QM) extension of the typical heat engine cycles, such as the Carnot, Brayton, Otto, Diesel cycles, etc., with no introduction of the concept of temperature. When these QM engine cycles are implemented by an ideal gas confined in an arbitrary power-law trap, a relation between the quantum adiabatic exponent and trap exponent is found. The differences and similarities between the efficiency of a given QM engine cycle and its classical counterpart are revealed and discussed.

Theory of indirect exciton photoluminescence in elevated quantum trap

Inspired by an experiment of indirect excitons photoluminescence (PL) in elevated quantum trap (High et al., 2009), we theoretically investigate the energy relaxation and nonlinear interactions of indirect excitons in coupled quantum wells. It is shown that, when increasing the laser power, the intensity reversion of two PL peaks is due to the phonon necklace effect. In addition, we use a nonlinear Schrödinger equation including attractive two-body, repulsive three-body interactions and the excitation power dependence of energy distribution to understand the exciton states. This model gives a natural account for the PL blue shift with the increase of the excitation power. This study thus provides an alternative way to understand the underlying physics of the exciton dynamics in coupled potential wells.

On a New Interpretation of Fuzzy C Mean Using Quantum Theory

A quantum mechanics interpretation of Fuzzy C-Mean (FCM) is presented. Cluster aims to study the data distribution in scale space. Its characteristics are very similar to the particle world in quantum physics. By analyzing the essence of the quantum potential and the quantum trap, the paper discusses the core and the basis of Quantum Clustering in quantum mechanics. A couple of drawbacks about Quantum Clustering algorithm is also presented. In addition, known from the fuzzy mathematical computing, the important fuzzy similarity parameter u in FCM is expressed by the quantum wave function. After a series of analysis, the important six innovation conclusions about Iris, FCM, and Quantum Clustering are proposed, and one of the most important is that there is a cryptical wave function existing in FCM, as well as several important experimental results prove it.

Under-coordinated atoms induced local strain, quantum trap depression and valence charge polarization at W stepped surfaces

We have explored the effects of atoms under-coordination on surface structure relaxation, binding energy shift of W stepped surfaces and valence charge polarization by the method of incorporating bond order-length-strength (BOLS) correlation mechanism into high-resolution X-ray photoluminescence spectra (XPS) measurements as well as density functional theory (DFT) calculations. Results show that the 4f 7/2 energy levels of bulk, surface skin and step edge W atoms shift deeper from 2.17 to 2.69 eV with respect to that of the isolated W (28.91±0.01 eV) atoms, while the valence charge energy shift upper from inner to outer layer and from bulk to stepped edge. The surface bond contraction occurs around under-coordinated atoms after geometry relaxation calculation. Consistency among BOLS calculations, DFT calculation and experimental measurements clarifies that the surface bond contraction and consolidation due to the effects of under-coordination atoms induce potential trap depression, which provides perturbation to the Hamiltonian and hence contributes to the surface core level shift deeper, and that the surface valence charge are polarized by the densely trapped core-level electrons to upper energy.

Phase diagram and deformed phase separation for a trapped Fermi gas with population imbalance and BCS pairing interaction

We study the phase separated state of an ultracold atomic Fermi gas confined in a three-dimensional quantum harmonic trap with a BCS pairing interaction. Examining various finite-temperature phase diagrams, we investigate the interplay between the filling of the quantum trap energy levels and the pairing energy. We find that a low (high) filling leads to a large (small) critical population imbalance for the superfluid/normal transition, together with a fully (partially) polarized normal part. We also show that the decrease of the density leads to a changeover of the shape of the superfluid core from an equipotential form to a deformed one. Moreover, we clarify the intrinsic mechanisms that lead to the deformation, providing a unified scenario for phase separation and deformation in a trapped Fermi gas, allowing for a possible interpretation of the apparently controversial experimental findings.

Interface quantum trap depression and charge polarization in the CuPd and AgPd bimetallic alloy catalysts

The ability of a catalyst to accept or donate charge is the key to the process of catalytic reaction. However, the determination of the catalytic nature of a specimen as yet remains a great challenge. Here we report an effective yet simple method for this purpose based on the tight binding theory considerations and XPS monitoring of the evolution of valence and core electrons upon alloy formation. Firstly, we measured the valence and core band charge density of the constituent elements of Cu, Ag, and Pd and then the respective states upon alloy formation. A subtraction of the resultant spectrum of the alloy by the composed elemental spectra gives the residual that shows clearly the occurrence of charge trapping or polarization. We found that the valence and the core electrons of the CuPd alloy shift positively to deeper energies, opposite to the occurrences in the AgPd alloy. Findings clarify for the first time that CuPd serves as an acceptor due to quantum trapping and the AgPd as a donor because of charge polarization, which also explain why AgPd and CuPd perform very differently as important catalysts.

Local structure relaxation, quantum trap depression, and valence charge polarization induced by the shorter-and-stronger bonds between under-coordinated atoms in gold nanostructures

Relativistic density functional theory calculations have been conducted to examine the effect of atomic under-coordination on the crystal structure, binding energy, and electron configuration of cuboctahedral and Marks decahedral gold clusters. Trend consistency between calculations and experimental observations confirmed the predictions made using BOLS correlation theory, suggesting that the shorter-and-stronger bonds between under-coordinated atoms induce local structure relaxation, potential well depression, and the associated local charge and energy densification, as well as the polarization of the otherwise conducting s-electrons (valence charge) by the densely- and tightly-trapped core electrons of which the binding energy shifts positively to deeper energies. Findings are in good agreement with scanning tunneling microscopy/spectroscopy results from monomers, dimers, chain ends, and nanostructures of gold and other metals.

Adatoms-Induced Local Bond Contraction, Quantum Trap Depression, and Charge Polarization at Pt and Rh Surfaces

The extremely high catalytic efficiency of undercoordinated noble metal adatoms is indeed fascinating, but its chemical and electronic origin remains yet puzzling. Incorporating the BOLS correlation theory [Sun, C. Q. Prog. Solid State Chem. 2007, 35, 1] into the high-resolution XPS measurements [Baraldi, A.; et al. New J. Phys. 2007, 9, 143; Bianchettin, L.; et al. J. Chem. Phys. 2008, 128, 114706] has affirmed the BOLS expectations that the broken bonds induce local strain and quantum trapping in addition to polarization of the otherwise conductive half-filled s-shell charge by the tightly- and densely-trapped inner electrons of the adatoms. Both the trapped and polarized states would be detectable from the density-of-states evolution of the valence and the core bands. The trapped states have been discovered at the bottom edges of Pt(5d106s0) 4f7/2 and Rh 3d5/2 bands, and the polarized states only present at the upper edge of Rh(4d85s1) 3d5/2. It is suggested that the quantum trapping increases the electroaffinity and the polarization does oppositely. Therefore, the Rh adatom serves as a donor and the Pt adatom as an acceptor in the process of catalytic reaction.

Trap states in oxidation layer of nanocrystal Si

The photoluminescence (PL) of nanocrystal present in porous silicon shifts from the near infrared to the ultraviolet depending on the size when the surface is passivated with Si-H bonds. After oxidation, the centre wavelength of PL band is pinned in a region of 700–750 nm and its intensity increases obviously. Calculation shows that trap electronic states appear in the band gap of a smaller nanocrystal when Si = O bonds or Si–O–Si bonds are formed. The changes in PL intensity and wavelength can be explained by both quantum confinement and trap states in an oxidation layer of nanocrystal. In the theoretical model, the most important factor in the enhancement and the pinning effects of PL emission is the relative position between the level of the trap states and the level of the photoexcitation in the silicon nanocrystal.