16,381 research outputs found
Charge echo in a Cooper-pair box
A spin-echo-type technique is applied to an artificial two-level system that
utilizes charge degree of freedom in a small superconducting electrode.
Gate-voltage pulses are used to produce the necessary pulse sequence in order
to eliminate the inhomogeneity effect in the time-ensemble measurement and to
obtain refocused echo signals. Comparison of the decay time of the observed
echo signal with estimated decoherence time suggests that low-frequency
energy-level fluctuations due to the 1/f charge noise dominate the dephasing in
the system.Comment: 4 pages, 3 figure
Information entropic superconducting microcooler
We consider a design for a cyclic microrefrigerator using a superconducting
flux qubit. Adiabatic modulation of the flux combined with thermalization can
be used to transfer energy from a lower temperature normal metal thin film
resistor to another one at higher temperature. The frequency selectivity of
photonic heat conduction is achieved by including the hot resistor as part of a
high frequency LC resonator and the cold one as part of a low-frequency
oscillator while keeping both circuits in the underdamped regime. We discuss
the performance of the device in an experimentally realistic setting. This
device illustrates the complementarity of information and thermodynamic entropy
as the erasure of the quantum bit directly relates to the cooling of the
resistor.Comment: 4 pages, 3 figure
Quantum Phase Transitions and the Hidden Order in a Two-Chain Extended Boson Hubbard Model at Half-Odd-Integer Fillings
We study the phase diagram of two weakly coupled one-dimensional dipolar
boson chains at half-odd-integer fillings. We find that the system contains a
rich phase diagram. Four different phases are found. They are the Mott
insulators, the single-particle resonant superfluid, the paired superfluid, and
the bond- or inter-chain density waves. Moreover, the Mott insulating phase can
be further classified according to a hidden string order parameter, which is
analogous to the one investigated recently in the one-dimensional boson Mott
insulator at integer fillings.Comment: 7 pages, 2 figure
Quantum noise in the Josephson charge qubit
We study decoherence of the Josephson charge qubit by measuring energy
relaxation and dephasing with help of the single-shot readout. We found that
the dominant energy relaxation process is a spontaneous emission induced by
quantum noise coupled to the charge degree of freedom. Spectral density of the
noise at high frequencies is roughly proportional to the qubit excitation
energy.Comment: Submitted to Phys. Rev. Letter
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