The robustness of magic state distillation against errors in Clifford gates

TL;DR

This paper analyzes how noise affects the process of magic state distillation in quantum computing, showing it remains effective under certain errors and could be practical for small-scale devices without full fault-tolerance.

Contribution

It investigates the robustness of magic state distillation against initial state perturbations and gate noise, highlighting its efficiency compared to fault-tolerance methods at low error rates.

Findings

Magic state distillation tolerates certain noise levels

Faulty distillation can outperform fault-tolerance at low errors

Noise impacts convergence rate and threshold in the protocol

Abstract

Quantum error correction and fault-tolerance have provided the possibility for large scale quantum computations without a detrimental loss of quantum information. A very natural class of gates for fault-tolerant quantum computation is the Clifford gate set and as such their usefulness for universal quantum computation is of great interest. Clifford group gates augmented by magic state preparation give the possibility of simulating universal quantum computation. However, experimentally one cannot expect to perfectly prepare magic states. Nonetheless, it has been shown that by repeatedly applying operations from the Clifford group and measurements in the Pauli basis, the fidelity of noisy prepared magic states can be increased arbitrarily close to a pure magic state [1]. We investigate the robustness of magic state distillation to perturbations of the initial states to arbitrary locations in the Bloch sphere due to noise. Additionally, we consider a depolarizing noise model on the quantum gates in the decoding section of the distillation protocol and demonstrate its effect on the convergence rate and threshold value. Finally, we establish that faulty magic state distillation is more efficient than fault-tolerance-assisted magic state distillation at low error rates due to the large overhead in the number of quantum gates and qubits required in a fault-tolerance architecture. The ability to perform magic state distillation with noisy gates leads us to conclude that this could be a realistic scheme for future small-scale quantum computing devices as fault-tolerance need only be used in the final steps of the protocol.