Robust magic state generation by utilizing state-dependent feedback for universal fault-tolerant quantum computing

A crucial element for universal quantum computation is the implementation of a non-Clifford gate[i]. However, non-Clifford gates are susceptible to errors during multiple gate operations, as stabilizer-based error-correcting codes cannot detect errors from non-Clifford gates. As an alternative to non-Clifford gate operations, the concept of non-Clifford state, referred to as a magic state, has been introduced. Magic state distillation (MSD), necessary for achieving a high-fidelity magic state, requires considerable overhead[ii][iii]. In this study, we propose a novel architecture for creating a magic state by leveraging the state-dependent response of a circuit quantum electrodynamics (QED) system. We demonstrate that the qubit state converges to an H-type magic state, regardless of its initial state, via a process we term magic state generation (MSG). This new architecture achieves MSG without massive multi-qubits overhead, offering a substantial improvement for realizing universal quantum computing.

[i] Nebe, G., Rains, E.M. & Sloane, N.J.A. (2001). The Invariants of the Clifford Groups. Designs, Codes and Cryptography 24, 99–122.

[ii] E. Knill. (2004). Fault-Tolerant Postselected Quantum Computation: Schemes.

[iii] Sergey Bravyi and Alexei Kitaev. (2005). Universal quantum computation with ideal Clifford gates and noisy ancillas. Phys. Rev. A 71, 022316.