Multiplexing Read-Out of Charge Qubits by a Superconducting Resonator

Wavelength division multiplexing (WDM) is widely used in modern optics and electronics. For future quantum computers, the integration of readout is also vitally important. Here we incorporate an idea of WDM to demonstrate multiplexing readout of charge qubits by using a single integrated on-chip superconducting microwave resonator. Two distant qubits formed by two graphene double quantum dots (DQDs) are simultaneously readout by an interconnected superconducting resonator. This readout device is found to have 2 MHz bandwidth and 1.1\times 10^-4\,\rm e/\sqrt\rm Hz charge sensitivity. Different frequency gate-modulations, which are used selectively to change the impedance of the qubits, are applied to different DQDs, which results in separated sidebands in the spectrum. These sidebands enable a multiplexing readout for the multi-qubits circuit. This architecture can largely reduce the amount of detectors and can improve the prospect for scaling-up of semiconductor qubits.