Mainz 2017 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 33: Quantum Information: Solid State Systems II
Q 33.5: Vortrag
Mittwoch, 8. März 2017, 15:30–15:45, P 3
High-Fidelity Parity Readout in the Nonlinear Dispersive Regime — •Marius Schöndorf1, Luke C. G. Govia1,2, and Frank K. Wilhelm-Mauch1 — 1Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany — 2Departement of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8
Superconducting qubits are promising candidate for the realization of a scalable quantum computer. An important step for real implementations is qubit state tomography. In the past we presented a scheme to readout sinlge qubit states as well as multiple parities with a microwave photon counter. Especially parity readout plays an important role for the implementation of error correction codes. Since most of the existing microwave photon counters do not have very high efficiencies, such that it is necessary to increase contrast in the readout cavity.
In this work we theoretically describe multiple qubits dispersively coupled to a driven cavity. We are especially interested in the regime where the linear dispersive approximation breaks down, which means the photon number in the cavity exceeds a specific number n > ncrit. To get a valid theoretical description of that system we need to use the exact dispersive transformation, which is also valid for high cavity occupation. The result is a nonlinear behavior for high drive strengths which has a strong dependence on the state of the N qubits coupled to the cavity which leads to a very high contrast of about 105 photons in the cavity. We show that this can be used to perform various multi qubit measurements with very high fidelity.