22,550 research outputs found
Controlling single-photon transport in waveguides with finite cross-section
We study the transverse-size effect of a quasi-one-dimensional rectangular
waveguide on the single-photon scattering on a two-level system. We calculate
the transmission and reflection coefficients for single incident photons using
the scattering formalism based on the Lippmann-Schwinger equation. When the
transverse size of the waveguide is larger than a critical size, we find that
the transverse mode will be involved in the single-photon scattering. Including
the coupling to a higher traverse mode, we find that the photon in the lowest
channel will be lost into the other channel, corresponding to the other
transverse modes, when the input energy is larger than the maximum bound-state
energy. Three kinds of resonance phenomena are predicted: single-photon
resonance, photonic Feshbach resonance, and cutoff (minimum) frequency
resonance. At these resonances, the input photon is completely reflected.Comment: 9 pages, 6 figure
On the heating of source of the Orion KL hot core
We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter
Scalable superconducting qubit circuits using dressed states
We study a coupling/decoupling method between a superconducting qubit and a
data bus that uses a controllable time-dependent electromagnetic field (TDEF).
As in recent experiments, the data bus can be either an LC circuit or a cavity
field. When the qubit and the data bus are initially fabricated, their detuning
should be made far larger than their coupling constant, so these can be treated
as two independent subsystems. However, if a TDEF is applied to the qubit, then
a "dressed qubit" (i.e., qubit plus the electromagnetic field) can be formed.
By choosing appropriate parameters for the TDEF, the dressed qubit can be
coupled to the data bus and, thus, the qubit and the data bus can exchange
information with the assistance of the TDEF. This mechanism allows the
scalability of the circuit to many qubits. With the help of the TDEF, any two
qubits can be selectively coupled to (and decoupled from) a common data bus.
Therefore, quantum information can be transferred from one qubit to another.Comment: 10 pages, 5 figure
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