Substrate removal near superconducting qubits and resonators in circuit QED processors

Xi Jiang, ziqiu zhang, Shi-Qing Tang

Circuit QED based on superconducting circuit structure is similar to the model of interaction between cavity field and atoms, and is solidified on the substrate, so it is more suitable for integration, expansion and control. The circuit QED system consists of resonators and superconducting qubits, the length of the resonators much larger than width, so it can be regarded as a one-dimensional linear planar structure in theory. We propose a theoretical model to realizing two-qubit photonic phase gate, we use two superconducting resonators to couple a magnetic flux qutrit via two capacitors in circuit QED system, and choose an appropriate interaction time, it turns out that a two-qubit photonic phase gate can be realized by one step.

Ivan N. Zhilyaev

Joel Strand

Dong‐Min Kim, Kyungsun Moon

We theoretically propose a circuit QED system implemented with a triple-leg stripline resonator (TSR). Unlike from a linear stripline resonator, the fundamental intracavity microwave modes of the TSR are twofold degenerate. When a superconducting qubit is placed near one of the TSR legs, one fundamental mode is directly coupled to the qubit, while the other one remains uncoupled. Using our circuit QED system, we have theoretically studied a two-qubit quantum gate operation in a hybrid qubit composed of a flying microwave qubit and a superconducting qubit. We have demonstrated that, for the hybrid qubit, the quantum controlled phase flip gate can be reliably implemented for the experimentally available set of parameters.

Wenhui Huang, Yuxuan Zhou, Ziyu Tao +5 more

We introduce a superconducting coplanar waveguide, in the form of a ring resonator, as a quantum bus for circuit quantum electrodynamics (circuit QED). Due to its unique symmetry, the amplitude of the electromagnetic field inside is uniform along the resonator, which in principle leads to a location independent coupling between qubits and the resonator. For an experimental demonstration, we designed and fabricated a ring resonator capacitively coupled to two tunable Xmon superconducting qubits. We showed that nearly identical coupling was achieved between individual qubits and the resonator. In addition, the resonator was also used as a high quality quantum bus for generating Bell states between the qubits with a fidelity of F=98.6%, although an interference effect must be included for understanding the effective coupling between the two qubits. Our results suggest that ring resonators can be a useful addition to the toolbox of circuit QED.

Shwetank Kumar, Matthias Steffen, David Peter Divincenzo +6 more