152 research outputs found
Controllable Coupling in Phase-Coupled Flux Qubits
We propose a scheme for tunable coupling of phase-coupled flux qubits. The
phase-coupling scheme can provide a strong coupling strength of the order of
Josephson coupling energy of Josephson junctions in the connecting loop, while
the previously studied inductive coupling scheme cannot provide due to small
mutual inductance and induced currents. We show that, in order to control the
coupling, we need {\it two} dc-SQUID's in the connecting loop and the control
fluxes threading the dc-SQUID's must be in {\it opposite} directions. The
coupling strength is analytically calculated as a function of the control flux
at the co-resonance point.Comment: version to appear in Phys. Rev.
Strong Coupling of a Cavity QED Architecture for a Current-biased Flux Qubit
We propose a scheme for a cavity quantum electrodynamics (QED) architecture
for a current-biased superconducting flux qubit with three Josephson junctions.
The qubit operation is performed by using a bias current coming from the
current mode of the circuit resonator. If the phase differences of junctions
are to be coupled with the bias current, the Josephson junctions should be
arranged in an asymmetric way in the qubit loop. Our QED scheme provides a
strong coupling between the flux qubit and the transmission line resonator of
the circuit.Comment: 5 pages, 3 figure
Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits
Superconducting flux qubits are considered to investigate macroscopic
many-qubit interactions.
Many-qubit states based on current states can be manipulated through the
current-phase relation in each superconducting loop.
For flux qubit systems comprised of qubit loops, a general expression of
low energy Hamiltonian is presented in terms of low energy levels of qubits and
macroscopic quantum tunnelings between the many-qubit states.
Many-qubit interactions classified by {\em Ising type- or tunnel-}exchange
interactions can be observable experimentally.
Flux qubit systems can provide various artificial-spin systems to study
many-body systems that cannot be found naturally.Comment: 5 pages, 1 figur
- …