Regensburg 2016 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 58: Transport: Poster Session
TT 58.11: Poster
Wednesday, March 9, 2016, 15:00–18:30, Poster D
Quantum state tomography on long-coherent superconducting transmon qubit — •Andre Schneider, Jochen Braumüller, Steffen Schlör, Martin Weides, and Alexey Ustinov — Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe
The state of a qubit is commonly measured by probing a readout resonator coupled to it with a readout tone and detecting the dispersive shift of the resonator. This measurement only gives access to the z-component of the qubit state. Quantum state tomography provides a measurement for all components of the Bloch vector by rotating the qubit state prior to the readout. We present a method of measuring the Bloch vector components. This method is demonstrated by measuring the time evolution for long-"living" transmon qubits with T1 and T2 times in excess of 10 µs. By recording the decay trace of the qubit state after a slightly detuned (π/2)x pulse, we detect decay and dephasing as well as Larmor precession of the qubit.
Furthermore, we introduce a benchmark for measuring the qubit manipulation fidelity and optimize the envelopes of the qubit manipulation pulses. Quantum state tomography is a powerful tool to observe changes in the qubit quantum state under interactions with magnonic systems.