13,829 research outputs found

    Quantum dynamics of non-relativistic particles and isometric embeddings

    Get PDF
    It is considered, in the framework of constrained systems, the quantum dynamics of non-relativistic particles moving on a d-dimensional Riemannian manifold M isometrically embedded in Rd+nR^{d+n}. This generalizes recent investigations where M has been assumed to be a hypersurface of Rd+1R^{d+1}. We show, contrary to recent claims, that constrained systems theory does not contribute to the elimination of the ambiguities present in the canonical and path integral formulations of the problem. These discrepancies with recent works are discussed.Comment: Revtex, 14 page

    Dissipation and detection of polaritons in ultrastrong coupling regime

    Full text link
    We have investigated theoretically a dissipative polariton system in the ultrastrong light-matter coupling regime without using the rotating-wave approximation on system-reservoir coupling. Photons in a cavity and excitations in matter respectively couple two large ensembles of harmonic oscillators (photonic and excitonic reservoirs). Inheriting the quantum statistics of polaritons in the ultrastrong coupling regime, in the ground state of the whole system, the two reservoirs are not in the vacuum states but they are squeezed and correlated. We suppose this non-vacuum reservoir state in the master equation and in the input-output formalism with Langevin equations. Both two approaches consistently guarantee the decay of polariton system to its ground state, and no photon detection is also obtained when the polariton system is in the ground state.Comment: 18 pages, 3 figure

    Preparation of macroscopic quantum superposition states of a cavity field via coupling to a superconducting charge qubit

    Full text link
    We propose how to generate macroscopic quantum superposition states using a microwave cavity containing a superconducting charge qubit. Based on the measurement of charge states, we show that the superpositions of two macroscopically distinguishable coherent states of a single-mode cavity field can be generated by a controllable interaction between a cavity field and a charge qubit. After such superpositions of the cavity field are created, the interaction can be switched off by the classical magnetic field, and there is no information transfer between the cavity field and the charge qubit. We also discuss the generation of the superpositions of two squeezed coherent states.Comment: 6 page

    Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosondes observations

    Full text link
    The results of contemporaneous summer nighttime observations of midlatitude medium scale traveling ionospheric disturbances (MSTIDs) with the Very Large Array (VLA) in New Mexico and nearby ionosondes in Texas and Colorado are presented. Using 132, 20-minute observations, several instances of MSTIDs were detected, all having wavefronts aligned northwest to southeast and mostly propagating toward the southwest, consistent with previous studies of MSTIDs. However, some were also found to move toward the northeast. It was found that both classes of MSTIDs were only found when sporadic-E (Es) layers of moderate peak density (1.5<foEs<3 MHz) were present. Limited fbEs data from one ionosonde suggests that there was a significant amount of structure with the Es layers during observations when foEs>3 MHz that was not present when 1.5<foEs<3 MHz. No MSTIDs were observed either before midnight or when the F-region height was increasing at a relatively high rate, even when these Es layers were observed. Combining this result with AE indices which were relatively high at the time (an average of about 300 nT and maximum of nearly 700 nT), it is inferred that both the lack of MSTIDs and the increase in F-region height are due to substorm-induced electric fields. The northeastward-directed MSTIDs were strongest post-midnight during times when the F-region was observed to be collapsing relatively quickly. This implies that these two occurrences are related and likely both caused by rare shifts in F-region neutral wind direction from southwest to northwest.Comment: Accepted for publication in the Journal of Geophysical Researc

    Effect Of Surface Charges On The Rates Of Intermolecular Electron-transfer Between De Novo Designed Metalloproteins

    Get PDF
    A de novo designed coiled-coil metalloprotein was prepared that uses electrostatic interactions to control both its conformational and bimolecular electron-transfer properties. The title protein exists as a coiled-coil heterodimer of the [Ru(trpy)(bpy)-KK(37-mer)] and [Ru(NH3)(5)-EE(37-mer)] polypeptides which is formed by interhelix electrostatic attractions. Circular dichroism studies show that the electrostatic heterodimer has Kd 0.19 +/- 0.03 muM and is 96% helical at high concentrations. Intercomplex electron-transfer reactions were studied that involve the [Ru(NH3)(5)-H21](2+) electron-donor and the [Ru(trpy)(bpy)H21](3+) electron-acceptor belonging to different electrostatic dimers. An important feature of the designed metalloprotein is its two cationic redox centers embedded within protein surfaces having opposite charge. Thus, the Ru-II(NH3)5-H21 site was placed on the surface of one chain of the coiled-coil which was made to be positively charged, and the Ru-III(trpy)(bpy)-H21 site was placed on the surface of the other chain which was negatively charged. The rates of intermolecular electron-transfer increased from (1.9 +/- 0.4) x 10(7) M-1 s(-1) to (3.7 +/- 0.5) x 107 M-1 s(-1) as the ionic strength was increased from 0.01 to 0.20 M. This indicates that the electrostatic repulsion between the ruthenium centers dominates the kinetics of these reactions. However, the presence of the oppositely charged protein surfaces in the coiled-coils creates an electrostatic recognition domain that substantially ameliorates the effects of this repulsion
    • …
    corecore