5,028 research outputs found
Quantum bit detector
We propose and analyze an experimental scheme of quantum nondemolition
detection of monophotonic and vacuum states in a superconductive toroidal
cavity by means of Rydberg atoms.Comment: 4 pages, 3 figure
About the dynamics and thermodynamics of trapped ions
This tutorial introduces the dynamics of charged particles in a
radiofrequency trap in a very general manner to point out the differences
between the dynamics in a quadrupole and in a multipole trap. When dense
samples are trapped, the dynamics is modified by the Coulomb repulsion between
ions. To take into account this repulsion, we propose to use a method,
originally developed for particles in Penning trap, that model the ion cloud as
a cold fluid. This method can not reproduce the organisation of cold clouds as
crystals but it allows one to scale the size of large samples with the trapping
parameters and the number of ions trapped, for different linear geometries of
trap.Comment: accepted for publication in the "Modern Applications of Trapped Ions"
special issu
Single microwave photon detection in the micromaser
High efficiency single photon detection is an interesting problem for many
areas of physics, including low temperature measurement, quantum information
science and particle physics. For optical photons, there are many examples of
devices capable of detecting single photons with high efficiency. However
reliable single photon detection of microwaves is very difficult, principally
due to their low energy. In this paper we present the theory of a cascade
amplifier operating in the microwave regime that has an optimal quantum
efficiency of 93%. The device uses a microwave photon to trigger the stimulated
emission of a sequence of atoms where the energy transition is readily
detectable. A detailed description of the detector's operation and some
discussion of the potential limitations of the detector are presented.Comment: 8 pages, 5 figure
Experimental realization of a quantum game on a one-way quantum computer
We report the first demonstration of a quantum game on an all-optical one-way
quantum computer. Following a recent theoretical proposal we implement a
quantum version of Prisoner's Dilemma, where the quantum circuit is realized by
a 4-qubit box-cluster configuration and the player's local strategies by
measurements performed on the physical qubits of the cluster. This
demonstration underlines the strength and versatility of the one-way model and
we expect that this will trigger further interest in designing quantum
protocols and algorithms to be tested in state-of-the-art cluster resources.Comment: 13 pages, 4 figure
Sequential Generation of Matrix-Product States in Cavity QED
We study the sequential generation of entangled photonic and atomic
multi-qubit states in the realm of cavity QED. We extend the work of C. Schoen
et al. [Phys. Rev. Lett. 95, 110503 (2005)], where it was shown that all states
generated in a sequential manner can be classified efficiently in terms of
matrix-product states. In particular, we consider two scenarios: photonic
multi-qubit states sequentially generated at the cavity output of a
single-photon source and atomic multi-qubit states generated by their
sequential interaction with the same cavity mode.Comment: 11 page
High fidelity transport of trapped-ion qubits through an X-junction trap array
We report reliable transport of 9Be+ ions through a 2-D trap array that
includes a separate loading/reservoir zone and an "X-junction". During
transport the ion's kinetic energy in its local well increases by only a few
motional quanta and internal-state coherences are preserved. We also examine
two sources of energy gain during transport: a particular radio-frequency (RF)
noise heating mechanism and digital sampling noise. Such studies are important
to achieve scaling in a trapped-ion quantum information processor.Comment: 4 pages, 3 figures Updated to reduce manuscript to four pages. Some
non-essential information was removed, including some waveform information
and more detailed information on the tra
Characterization of Poly(A)-Protein Complexes Isolated from Free and Membrane-Bound Polyribosomes of Ehrlich Ascites Tumor Cells
Proteins present in messenger ribonucleoprotein particles were labeled with [35S]-methionine in Ehrlich ascites tumor cells in which synthesis of new ribosomes was inhibited. Poly(A)-protein complexes were isolated from free and membrane-bound polyribosomes by sucrose gradient centrifugation and affinity chromatography on oligo(dT)-cellulose. Both classes of Poly(A)-protein particles contain a poly(A) chain of about 70 adenyl residues and a protein with a molecular weight of 76000 attached to it
Distributed coherent manipulation of qutrits by virtual excitation processes
We propose a scheme for the deterministic coherent manipulation of two atomic
qutrits, trapped in separate cavities coupled through a short optical fibre or
optical resonator. We study such a system in the regime of dispersive
atom-field interactions, where the dynamics of atoms, cavities and fibre
operates through virtual population of both the atomic excited states and
photonic states in the cavities and fibre. We show that the resulting effective
dynamics allows for the creation of robust qutrit entanglement, and thoroughly
investigate the influence of imperfections and dissipation, due to atomic
spontaneous emission and photon leakage, on the entanglement of the two qutrits
state.Comment: 15 pages, 4 figure
Attosecond double-slit experiment
A new scheme for a double-slit experiment in the time domain is presented.
Phase-stabilized few-cycle laser pulses open one to two windows (``slits'') of
attosecond duration for photoionization. Fringes in the angle-resolved energy
spectrum of varying visibility depending on the degree of which-way information
are observed. A situation in which one and the same electron encounters a
single and a double slit at the same time is discussed. The investigation of
the fringes makes possible interferometry on the attosecond time scale. The
number of visible fringes, for example, indicates that the slits are extended
over about 500as.Comment: 4 figure
Macroscopic Interference Effects in Resonant Cavities
We investigate the possibility of interference effects induced by macroscopic
quantum-mechanical superpositions of almost othogonal coherent states - a
Schroedinger cats state - in a resonant microcavity. Despite the fact that a
single atom, used as a probe of the cat state, on the average only change the
mean number of photons by one unit, we show that this single atom can change
the system drastically. Interference between the initial and almost orthogonal
macroscopic quantum states of the radiation field can now take place.
Dissipation under current experimental conditions is taken into account and it
is found that this does not necessarily change the intereference effects
dramatically.Comment: 20 pages, 3 figure
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