Robust Quantum Gates in Decoherence-Free Subspaces with Josephson Charge Qubits

Abstract

We propose a new and feasible scheme to implement quantum gates in decoherence-free subspaces (DFSs) with Josephson charge qubits situated in a circuit QED architecture. Based on the resonator-assisted interaction, the controllable interqubit couplings occur only by tuning the individual flux biases, by which we obtain the DFS-encoded universal quantum gates. Compared with the non-DFS situation, we numerically consider the robustness of the DFS-encoded scheme that can be insensitive to the collective noises. Thus the protocol may perform the fault-tolerant quantum computing with Josephson charge qubits.

Robust Quantum Computing in Decoherence-Free Subspaces with Double-Dot Spin Qubits

“…Through the TLR in circuit QED setup, the selective and controllable interqubit couplings can be realized only by adjusting the detuning between transition frequencies of qubits, which thus provide the preferable conditions to construct the scalable quantum information processing. [1] Different from the previous case, [37] the noise effects on semiconductor spin qubits in the present scheme are the pure dephasing mainly. [10,17] The DFS-encoded protocol is just useful to eliminate the dephasing effects originated from the σ z -type collective noises, and therefore the gate fidelities can be enhanced significantly.…”

“…Due to the virtual exchange of photons, the effects of the photon leakages on the evolution processes can be neglected safely. [12,37] Theoretically, the DFS-encoded scheme is not affected by the σ z -type collective noises, which is the pivotal reason for performing robust quantum gates. Through calculating Eq.…”