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M. Baur

Publications and source records attributed to M. Baur.

20 records · Page 2Linked to original sources

Two-Qubit State Tomography using a Joint Dispersive Read-Out

Quantum state tomography is an important tool in quantum information science for complete characterization of multi-qubit states and their correlations. Here we report a method to perform a joint simultaneous read-out of two superconducting qubits dispersively coupled to the same mode of a microwave transmission line resonator. The non-linear dependence of the resonator transmission on the qubit state dependent cavity frequency allows us to extract the full two-qubit correlations without the need for single shot read-out of individual qubits. We employ standard tomographic techniques to reconstruct the density matrix of two-qubit quantum states.

cond-mat.mes-hall↗

Coplanar Waveguide Resonators for Circuit Quantum Electrodynamics

We have designed and fabricated superconducting coplanar waveguide resonators with fundamental frequencies from 2 to $9 \rm{GHz}$ and loaded quality factors ranging from a few hundreds to a several hundred thousands reached at temperatures of $20 \rm{mK}$. The loaded quality factors are controlled by appropriately designed input and output coupling capacitors. The measured transmission spectra are analyzed using both a lumped element model and a distributed element transmission matrix method. The experimentally determined resonance frequencies, quality factors and insertion losses are fully and consistently characterized by the two models for all measured devices. Such resonators find prominent applications in quantum optics and quantum information processing with superconducting electronic circuits and in single photon detectors and parametric amplifiers.

cond-mat.supr-con↗