75 research outputs found
Demonstration of Geometric Landau-Zener Interferometry in a Superconducting Qubit
Geometric quantum manipulation and Landau-Zener interferometry have been
separately explored in many quantum systems. In this Letter, we combine these
two approaches to study the dynamics of a superconducting phase qubit. We
experimentally demonstrate Landau-Zener interferometry based on the pure
geometric phases in this solid-state qubit. We observe the interference caused
by a pure geometric phase accumulated in the evolution between two consecutive
Landau-Zener transitions, while the dynamical phase is canceled out by a
spin-echo pulse. The full controllability of the qubit state as a function of
the intrinsically robust geometric phase provides a promising approach for
quantum state manipulation.Comment: 5 pages + 3 pages supplemental Materia
Rapid characterization of microscopic two-level systems using Landau-Zener transitions in a superconducting qubit
This is the published version. Copyright 2015 American Institute of PhysicsWe demonstrate a fast method to detect microscopic two-level systems in a superconducting phase qubit. By monitoring the population leak after sweeping the qubit bias flux, we are able to measure the two-level systems that are coupled with the qubit. Compared with the traditional method that detects two-level systems by energy spectroscopy, our method is faster and more sensitive. This method supplies a useful tool to investigate two-level systems in solid-state qubits
Accelerated quantum adiabatic transfer in superconducting qubits
Quantum adiabatic transfer is widely used in quantum computation and quantum
simulation. However, the transfer speed is limited by the quantum adiabatic
approximation condition, which hinders its application in quantum systems with
a short decoherence time. Here we demonstrate quantum adiabatic state transfers
that jump along geodesics in one-qubit and two-qubit superconducting transmons.
This approach possesses the advantages of speed, robustness, and high fidelity
compared with the usual adiabatic process. Our protocol provides feasible
strategies for improving state manipulation and gate operation in
superconducting quantum circuits
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