Research On The Read Out Of A Tunable Resonator Via A Transmission Line

Quantum bits (Qubit), which can be realized with many physical systems such as quantum dots, trapped ions and Josephson junctions, are the foundation of a quantum computer. Because superconducting qubit can be easily controlled through adjusting the external parameters and scaled to many qubits, it has become one of the most promising candidates to realize a practical quantum computer. Because the realization of quantum computer needs more than one qubit, one of the problems in the superconducting qubits is how to read multiple qubits’states. Superconducting coplanar waveguide resonator can be used not only to read out the quantum states, but also to couple multiple qubits. Besides, through the coupling between a transmission line and a coplanar waveguide resonator, we can read multiple signals simultaneously.Here we have fabricated several λ/4 resonators on the high-resistivity silicon substrate. By connecting the resonator with a dc-SQUID to the ground, we have obtained a tunable superconducting coplanar waveguide resonator.At low temperature (T<10 mK), through a common microwave transmission line coupled to all resonators, we measured the resonant frequency of the frequency-tunable resonator with a variable external magnetic flux bias. The experimental results agree well with the theoretical ones.