1,172 research outputs found
Hybridized solid-state qubit in the charge-flux regime
Most superconducting qubits operate in a regime dominated by either the
electrical charge or the magnetic flux. Here we study an intermediate case: a
hybridized charge-flux qubit with a third Josephson junction (JJ) added into
the SQUID loop of the Cooper-pair box. This additional JJ allows the optimal
design of a low-decoherence qubit. Both charge and flux noises are
considered. Moreover, we show that an efficient quantum measurement of either
the current or the charge can be achieved by using different area sizes for the
third JJ.Comment: 7 pages, 5 figures. Phys. Rev. B, in pres
Optomechanical-like coupling between superconducting resonators
We propose and analyze a circuit that implements a nonlinear coupling between
two superconducting microwave resonators. The resonators are coupled through a
superconducting quantum interference device (SQUID) that terminates one of the
resonators. This produces a nonlinear interaction on the standard
optomechanical form, where the quadrature of one resonator couples to the
photon number of the other resonator. The circuit therefore allows for
all-electrical realizations of analogs to optomechanical systems, with coupling
that can be both strong and tunable. We estimate the coupling strengths that
should be attainable with the proposed device, and we find that the device is a
promising candidate for realizing the single-photon strong-coupling regime. As
a potential application, we discuss implementations of networks of
nonlinearly-coupled microwave resonators, which could be used in
microwave-photon based quantum simulation.Comment: 10 pages, 7 figure
Correlation-induced suppression of decoherence in capacitively coupled Cooper-pair boxes
Charge fluctuations from gate bias and background traps severely limit the
performance of a charge qubit in a Cooper-pair box (CPB). Here we present an
experimentally realizable method to control the decoherence effects of these
charge fluctuations using two strongly capacitively coupled CPBs. This
coupled-box system has a low-decoherence subspace of two states. Our results
show that the inter-box Coulomb correlation can help significantly suppress
decoherence of this two-level system, making it a promising candidate as a
logical qubit, encoded using two CPBs.Comment: 5 pages, 2 figures. Phys. Rev. B, in pres
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