We study a voltage-controlled version of the superconducting flux qubit [Chiorescu et al., Science 299, 1869 (2003)] and show that full control of qubit rotations on the entire Bloch sphere can be achieved. Circuit graph theory is used to study a setup where voltage sources are attached to the two superconducting islands formed between the three Josephson junctions in the flux qubit. Applying a voltage allows qubit rotations about the $y$ axis, in addition to pure $x$ and $z$ rotations obtained in the absence of applied voltages. The orientation and magnitude of the rotation axis on the Bloch sphere can be tuned by the gate voltages, the external magnetic flux, and the ratio $\ensuremath{\alpha}$ between the Josephson energies of the junctions via a flux-tunable junction. We compare the single-qubit control in the known regime $\ensuremath{\alpha}<1$ with the unexplored range $\ensuremath{\alpha}>1$ and estimate the decoherence due to voltage fluctuations.We study a voltage-controlled version of the superconducting flux qubit [Chiorescu et al., Science 299, 1869 (2003)] and show that full control of qubit rotations on the entire Bloch sphere can be achieved. Circuit graph theory is used to study a setup where voltage sources are attached to the two superconducting islands formed between the three Josephson junctions in the flux qubit. Applying a voltage allows qubit rotations about the $y$ axis, in addition to pure $x$ and $z$ rotations obtained in the absence of applied voltages. The orientation and magnitude of the rotation axis on the Bloch sphere can be tuned by the gate voltages, the external magnetic flux, and the ratio $\ensuremath{\alpha}$ between the Josephson energies of the junctions via a flux-tunable junction. We compare the single-qubit control in the known regime $\ensuremath{\alpha}<1$ with the unexplored range $\ensuremath{\alpha}>1$ and estimate the decoherence due to voltage fluctuations.

arXiv:cond-mat/0606587Physical Review BNov 15, 200620 citations

Ising interaction between capacitively-coupled superconducting flux qubits

Takahiko Satoh, Yuichiro Matsuzaki, Kosuke Kakuyanagi +3 more

Here, we propose a scheme to generate a controllable Ising interaction between superconducting flux qubits. Existing schemes rely on inducting couplings to realize Ising interactions between flux qubits, and the interaction strength is controlled by an applied magnetic field On the other hand, we have found a way to generate an interaction between the flux qubits via capacitive couplings. This has an advantage in individual addressability, because we can control the interaction strength by changing an applied voltage that can be easily localized. This is a crucial step toward the realizing superconducting flux qubit quantum computation.Here, we propose a scheme to generate a controllable Ising interaction between superconducting flux qubits. Existing schemes rely on inducting couplings to realize Ising interactions between flux qubits, and the interaction strength is controlled by an applied magnetic field On the other hand, we have found a way to generate an interaction between the flux qubits via capacitive couplings. This has an advantage in individual addressability, because we can control the interaction strength by changing an applied voltage that can be easily localized. This is a crucial step toward the realizing superconducting flux qubit quantum computation.

arXiv:1501.07739Jan 30, 20155 citations

A superconducting flux qubit with tunable tunnel coupling

Simon Gustavsson, Jonas Bylander, Fumiki Yoshihara +4 more

Bulletin of the American Physical SocietyMar 18, 20100 citations

y

axis, in addition to pure

x

and

z

rotations obtained in the absence of applied voltages. The orientation and magnitude of the rotation axis on the Bloch sphere can be tuned by the gate voltages, the external magnetic flux, and the ratio $\ensuremath{\alpha}$ between the Josephson energies of the junctions via a flux-tunable junction. We compare the single-qubit control in the known regime $\ensuremath{\alpha}<1$ with the unexplored range $\ensuremath{\alpha}>1$ and estimate the decoherence due to voltage fluctuations.