Composite pulses for quantum computation with trapped electrons

In a scalable quantum computer, based on trapped electrons in vacuum, qubits are encoded in the external (cyclotron motion) and internal (spin) degrees of freedom. We show how to extend the technique of composite pulses to manipulate the cyclotron oscillator without leaving the computational subspace. In particular, we describe and discuss how to implement the explicit pulse sequence which operates the conditional phase shift between the cyclotron and the spin qubits.     

Scalable solid-state quantum processor using subradiant two-atom states

We propose a realization of a scalable, high-performance quantum processor whose qubits are represented by the ground and subradiant states of effective dimers formed by pairs of two-level systems coupled by resonant dipole-dipole interaction. The dimers are implanted in low-temperature solid host material at controllable nanoscale separations. The two-qubit entanglement either relies on the coherent excitation exchange between the dimers or is mediated by external laser fields.     

Energy distribution of trapped electrons

Electrons have been trapped in an electrostatic quadrupole trap with superimposed homogeneous field of a superconducting magnet. Changes of their energy distribution due to synchrotron radiation cooling or due to resonant cyclotron excitation have been observed.     

Experimental study of intense screw beams with trapped electrons

The velocity spread and average oscillatory energy of intense screw beams of gyrotrons are experimentally studied in the presence of electrons reflected from a magnetic mirror and captured in an adiabatic trap. The results of the experiments indicate a significant influence of trapped electrons on the parameters of beams, especially in systems forming quasilaminar beams. Modifications of magnetron-injector guns are considered in which a certain reduction of the influence of reflected electrons is reached.Institute of Applied Physics, Russian Academy of Science, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 8, pp. 860–869, August, 1995.     

Surface trapped excess electrons on ice

Local trapping of excess electrons at the surface of solid water systems has recently been observed in large water clusters and at the ice/vacuum interface. The existence of stable surface-bound states for the excess electron may have important implications in atmospheric chemistry, electrochemistry, and radiation physics. By means of first-principles molecular dynamics we find that excess electrons induce a structural reconstruction of the ice surface on a time scale of a fraction of a picosecond. The surface molecular rearrangement leads to an increase of the number of dangling OH bonds pointing towards the vacuum and to the appearance of an electrostatic barrier preventing the penetration of the electron in the bulk. Both factors imply a remarkable stability for the surface-bound excess electron, with respect to its decay into the bulk solvated state.     

Scalable quantum computing with Josephson charge qubits

A goal of quantum information technology is to control the quantum state of a system, including its preparation, manipulation, and measurement. However, scalability to many qubits and controlled con-nectivity between any selected qubits are two of the major stumbling blocks to achieve quantum com-puting (QC). Here we propose an experimental method, using Josephson charge qubits, to efficiently solve these two central problems. The proposed QC architecture is scalable since any two charge qubits can be effectively coupled by an experimentally accessible inductance. More importantly, we formulate an efficient and realizable QC scheme that requires only one (instead of two or more) two-bit operation to implement conditional gates.     

Effective quantum spin systems with trapped ions

We show that the physical system consisting of trapped ions interacting with lasers may undergo a rich variety of quantum phase transitions. By changing the laser intensities and polarizations the dynamics of the internal states of the ions can be controlled, in such a way that an Ising or Heisenberg-like interaction is induced between effective spins. Our scheme allows us to build an analogue quantum simulator of spin systems with trapped ions, and observe and analyze quantum phase transitions with unprecedented opportunities for the measurement and manipulation of spins.     

Programmable quantum processor implemented with superconducting circuit

A quantum processor might execute certain computational tasks exponentially faster than a classical processor. Here, using superconducting quantum circuits we design a powerful universal quantum processor with the structure of symmetric all-to-all capacitive connection. We present the Hamiltonian and use it to demonstrate a full set of qubit operations needed in the programmable universal quantum computations. With the device the unwanted crosstalk and ZZ-type couplings between qubits can be effectively suppressed by tuning gate voltages, and the design allows efficient and high-quality couplings of qubits. Within available technology,the scheme may enable a practical programmable universal quantum computer.     

Nonlinear dust-ion-acoustic waves in a multi-ion plasma with trapped electrons

A dusty multi-ion plasma system consisting of non-isothermal (trapped) electrons, Maxwellian (isothermal) light positive ions, warm heavy negative ions and extremely massive charge fluctuating stationary dust have been considered. The dust-ion-acoustic solitary and shock waves associated with negative ion dynamics, Maxwellian (isothermal) positive ions, trapped electrons and charge fluctuating stationary dust have been investigated by employing the reductive perturbation method. The basic features of such dust-ion-acoustic solitary and shock waves have been identified. The implications of our findings in space and laboratory dusty multi-ion plasmas are discussed.     

Interaction of electrons and molecules with a single trapped nanoparticle

Highresolution nanoparticle mass spectrometry (NPMS) is used to study the interaction of electrons and molecules with the surface of a single, isolated particle stored in a three-dimensional quadrupole trap over weeks. IR-laser heating is employed as a fast temperature control. The kinetics of adsorption and desorption of molecules is studied for a 500-nm-diameter SiO₂ particle. A C₆₀ multilayer film has been prepared during online NPMS monitoring. Emission probabilities for secondary electrons are determined for a bare particle and a particle with a 40-nm-thick layer of C₆₀. From the molecular desorption rates (fg/h) at constant temperature binding energies of multilayer 1.47-eV and submonolayer 1.53-eV C₆₀ have been determined. Future perspectives of this new surface-science technique are discussed. PACS 68.43.Mn; 81.15.Ef; 81.70.Pg; 81.70.Fy     

Shock waves in magnetized plasmas with superthermal trapped electrons.

Formation of ion-acoustic shock waves (IAShWs) and their propagation nature in a magnetized plasma in the presence of superthermal trapped electrons are investigated for the first time via the fluid dynamical approach. A magnetized plasma system, comprising of inertial ions and non-inertial electrons following $\kappa$-superthermal trapped distribution, is considered to examine the basic features (amplitude, width, phase speed, etc.) of IAShWs in such a plasma. A diffusion effect (due to the ion kinematic viscosity) is taken into account. The reductive perturbation technique is adopted to derive the modified Korteweg de-Vries Burgers’ (mKdVB) equation and the solution of mKdVB equation (derived by adopting the tangent hyperbolic method) is used to investigate the dynamical and structural characteristics (speed, amplitude, width, etc.) of IAShWs. The influence of relevant plasma (configuration) parameters (e.g., the superthermality index $\kappa ,$ concentration of trapped electrons, external magnetic field, and obliquity angle, etc.) on the nature of IAShWs is examined. The applications of the results in space and laboratory plasma environments, where nonthermal trapped electrons are available, are briefly discussed.     

Polarization detection of trapped electrons via interaction with polarized atoms

Electrons were trapped in an electrostatic quadrupole trap with superimposed homogeneous magnetic field. The electrons were polarized by spin exchange with a polarized atomic beam. The free trapped electron polarization was converted to a change in the electron translational energy via spin-dependent inelastic collisions with the atomic beam, and the electron translational temperature was monitored. Discussed are the development of this variation of the measurement technique, characteristics of electron storage, and the electron-polarized atom inelastic interaction as a function of electron temperature and time. The method has been applied to the detection of the (g-2) resonance of free, stored electrons.     

Contribution to the theory of helical beams with trapped electrons

Institute of Applied Physics, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 12, pp. 1406–1411, December, 1990.     

ECRH of trapped electrons in laboratory magnetoplasmas

Heating of plasma electrons by high power millimeter wave fields at cyclotron harmonic resonance is studied. A mirror field is modelled for the local trapping of electrons. It is shown that superthermal electrons can be generated as the consequence of the ECRH of trapped electrons.     

Harmonically trapped ideal quantum gases

We solve the problem of a Bose or Fermi gas in d-dimensions trapped by δ ⩽ d mutually perpendicular harmonic oscillator potentials. From the grand potential we derive their thermodynamic functions (internal energy, specific heat, etc.) as well as a generalized density of states. The Bose gas exhibits Bose-Einstein condensation at a nonzero critical temperature T _c if and only if d + δ > 2, along with a jump in the specific heat at T _c if and only if d + δ > 4. Specific heats for both gas types precisely coincide as functions of temperature when d + δ = 2. The trapped system behaves like an ideal free quantum gas in d + δ dimensions. For δ = 0 we recover all known thermodynamic properties of ideal quantum gases in d dimensions, while in 3D for δ = 1, 2 and 3 one simulates behavior reminiscent of quantum wells, wires anddots, respectively. Good agreement is found between experimental critical temperatures for the trapped boson gases ₃₇ ⁸⁷Rb, ₃ ⁷Li, ₃₇ ⁸⁵Rb, ₂ ⁴He, ₁₉ ⁴¹K and the known theoretical expression which is a special case for d = δ = 3, but only moderate agreement for ₁₁ ²⁷Na and ₁ ¹H. Received 17 July 2002 / Received in final form 14 October 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: mdgg@hp.fciencias.unam.mx     

Modulational instability of relativistic ion-acoustic waves in aplasma with trapped electrons

The association between the modified Korteweg-de Vries solitary wave and the modulationally unstable envelope solitary wave in a weakly relativistic unmagnetized plasma with trapped electrons is discussed. The effect of trapped electrons modifies the nonlinearity of the nonlinear Schrodinger equation and gives rise to the propagation of the modulationally unstable ion-acoustic solitary wave. The amplitude of the envelope solitary wave increases while the number of trapped electrons decreases. The velocity of the solitary wave decreases with increasing ionic temperature and increasing particle velocities. The ion oscillation mode, which satisfies the nonlinear dispersion relation, is also derived. The theory is applied to explain space observations of the solar energetic flows in interplanetary space and of the energetic particle events in the Earth's magnetosphere     

Synchrotron radiation of electrons trapped in earth's magnetosphere

Relatively large fluxes of trapped electrons with energy above several tens of MeV in the inner radiation belt, established according to low altitude satellite measurements, invoked the question of their production of synchrotron radiation in geomagnetic field. Based on experimental data on electrons, rough estimate of the spectral density of synchrotron radiation at the Equator is obtained in the region of maximum emissivity. Relatively low value of the radiation flux implies that only precise measurements at 1 GHz allowing to measure the directivity of emissions may be relevant.     

Motion of trapped electrons in gyro-resonant electromagnetic field

It is shown that the phase space of magnetically trapped electrons in plasmas interacting with gyro-resonant electromagnetic waves is divided into two parts. In one, as a particle gains energy its turning point moves towards the region of weaker magnetic field; in the other, energy gain results in the turning point moving towards the region of stronger magnetic field, with possible detrapping.     

Performance of quantum phase gates with cold trapped atoms

We examine the performance of a quantum phase gate implemented with cold neutral atoms in microtraps, when anharmonic traps are employed and the effects of finite temperature are also taken into account. Both the anharmonicity and the temperature are found to pose limitations to the performance of the quantum gate. We present a quantitative analysis of the problem and show that the phase gate has a high quality performance for the experimental values that are presently or in the near future achievable in the laboratory.