Universal quantum computation in a decoherence-free subspace for collective relaxation with transmon qubits
Zu-Rong Zhang, Chun-Wang Wu, Chunyan Li, Hong‐Yi Dai, Cheng-Zu Li · Physical Review A · 2013
For the transmon, its dephasing has experimentally been suppressed to an extent that dephasing time is mainly limited by the relaxation process [Schreier et al., Phys. Rev. B 77, 180502(R) (2008)]. In the Hilbert space of two transmons, there exists a two-dimensional subspace immune to the collective relaxation. In this paper, by encoding a logical qubit in this subspace, we demonstrate how to realize universal quantum computation in the decoherence-free subspace. In our scheme, the transmons are coupled through a one-dimensional superconducting transmission-line resonator. With the help of some classical driving fields, two noncommutable single-logical-qubit rotation operators and a controlled-phase gate between two logical qubits are obtained. We always work in the detuning regime, which largely decreases relaxation induced by the Purcell effect.