6,233 research outputs found
Variable-frequency-controlled coupling in charge qubit circuits: Effects of microwave field on qubit-state readout
To implement quantum information processing, microwave fields are often used
to manipulate superconuducting qubits. We study how the coupling between
superconducting charge qubits can be controlled by variable-frequency magnetic
fields. We also study the effects of the microwave fields on the readout of the
charge-qubit states. The measurement of the charge-qubit states can be used to
demonstrate the statistical properties of photons.Comment: 7 pages, 3 figure
Switchable coupling between charge and flux qubits
We propose a hybrid quantum circuit with both charge and flux qubits
connected to a large Josephson junction that gives rise to an effective
inter-qubit coupling controlled by the external magnetic flux. This switchable
inter-qubit coupling can be used to transfer back and forth an arbitrary
superposition state between the charge qubit and the flux qubit working at the
optimal point. The proposed hybrid circuit provides a promising quantum memory
because the flux qubit at the optimal point can store the tranferred quantum
state for a relatively long time.Comment: 5 pages, 1 figur
Optical selection rules and phase-dependent adiabatic state control in a superconducting quantum circuit
We analyze the optical selection rules of the microwave-assisted transitions
in a flux qubit superconducting quantum circuit (SQC). We show that the
parities of the states relevant to the superconducting phase in the SQC are
well-defined when the external magnetic flux , then the
selection rules are same as the ones for the electric-dipole transitions in
usual atoms. When , the symmetry of the potential of
the artificial "atom'' is broken, a so-called -type "cyclic"
three-level atom is formed, where one- and two-photon processes can coexist. We
study how the population of these three states can be selectively transferred
by adiabatically controlling the electromagnetic field pulses. Different from
-type atoms, the adiabatic population transfer in our three-level
-atom can be controlled not only by the amplitudes but also by the
phases of the pulses
Measuring the quality factor of a microwave cavity using superconduting qubit devices
We propose a method to create superpositions of two macroscopic quantum
states of a single-mode microwave cavity field interacting with a
superconducting charge qubit. The decoherence of such superpositions can be
determined by measuring either the Wigner function of the cavity field or the
charge qubit states. Then the quality factor Q of the cavity can be inferred
from the decoherence of the superposed states. The proposed method is
experimentally realizable within current technology even when the value is
relatively low, and the interaction between the qubit and the cavity field is
weak.Comment: 8 page
Entanglement dynamics of Nitrogen-vacancy centers spin ensembles coupled to a superconducting resonator
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