38,989 research outputs found
Inconsistences in Interacting Agegraphic Dark Energy Models
It is found that the origin agegraphic dark energy tracks the matter in the
matter-dominated epoch and then the subsequent dark-energy-dominated epoch
becomes impossible. It is argued that the difficulty can be removed when the
interaction between the agegraphic dark energy and dark matter is considered.
In the note, by discussing three different interacting models, we find that the
difficulty still stands even in the interacting models. Furthermore, we find
that in the interacting models, there exists the other serious inconsistence
that the existence of the radiation/matter-dominated epoch contradicts the
ability of agegraphic dark energy in driving the accelerated expansion. The
contradiction can be avoided in one of the three models if some constraints on
the parameters hold.Comment: 12 pages, no figure; analysis is added; conclusion is unchange
Quantum decoherence of excitons in a leaky cavity with quasimode
For the excitons in the quantum well placed within a leaky cavity, the
quantum decoherence of a mesoscopically superposed states is investigated based
on the factorization theory for quantum dissipation. It is found that the
coherence of the exciton superposition states will decrease in an oscillating
form when the cavity field interacting with the exciton is of the form of
quasimode. The effect of the thermal cavity fields on the quantum decoherence
of the superposition states of the exciton is studied and it is observed that
the higher the temperature of the environment is, the shorter the decoherence
characteristic time is.Comment: 1 figure, 7 page
Strategy for designing broadband epsilon-near-zero metamaterial with loss compensation by gain media
A strategy is proposed to design the broadband gain-doped epsilon-near-zero
(GENZ) metamaterial. Based on the Milton representation of effective
permittivity, the strategy starts in a dimensionless spectral space, where the
effective permittivity of GENZ metamaterial is simply determined by a pole-zero
structure corresponding to the operating frequency range. The physical
structure of GENZ metamaterial is retrieved from the pole-zero structure via a
tractable inverse problem. The strategy is of great advantage in practical
applications and also theoretically reveals the cancellation mechanism
dominating the broadband near-zero permittivity phenomenon in the spectral
space
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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