David P. DiVincenzo

High-Coherence Hybrid Superconducting Qubit

We report quantum coherence measurements of a superconducting qubit whose design is a hybrid of several existing types. Excellent coherence times are found: T2∼T1∼1.5 μs. The topology of the qubit is that of a traditional three-junction flux qubit, but it has a large shunting capacitance, and the ratio of the junction critical currents is chosen so that the qubit potential has a single-well form. The qubit has a sizable nonlinearity, but its sign is reversed compared with most other popular qubit designs. The qubit is read out dispersively using a high-Q resonator in a λ/2 configuration.

Anisotropic spin exchange in pulsed quantum gates.

We show how to eliminate the first-order effects of the spin-orbit interaction in the performance of a two-qubit quantum gate. Our procedure involves tailoring the time dependence of the coupling between neighboring spins. We derive an effective Hamiltonian which permits a systematic analysis of this tailoring. Time-symmetric pulsing of the coupling automatically eliminates several undesirable terms in this Hamiltonian. Well chosen pulse shapes can produce an effectively isotropic exchange gate, which can be used in universal quantum computation with appropriate coding.

High-Kinetic-Inductance Superconducting Nanowire Resonators for Circuit QED in a Magnetic Field

We present superconducting microwave-frequency resonators based on NbTiN nanowires. The small cross section of the nanowires minimizes vortex generation, making the resonators resilient to magnetic fields. Measured intrinsic quality factors exceed

Quantum computing: an IBM perspective

2times 10^5

From Majorana fermions to topological order.

in a

Majorana Braiding with Thermal Noise.

6

Two-qubit couplings of singlet-triplet qubits mediated by one quantum state

T in-plane magnetic field, and

Multi-qubit parity measurement in circuit quantum electrodynamics

3times 10^4

Quantum Circuits for Measuring Levin-Wen Operators

in a

Fault-tolerant quantum computation for singlet-triplet qubits with leakage errors

350