Bespoke Pulse Design for Robust Rapid Two-Qubit Gates with Trapped Ions

TL;DR

This paper introduces a novel quantum control method for designing robust, rapid two-qubit gates in trapped-ion systems, accounting for complex physical effects without fitting parameters, to enhance scalability in quantum computing.

Contribution

The paper presents a comprehensive quantum master equation-based optimization approach for pulse design, improving gate robustness and speed in ion-trap quantum computing.

Findings

Achieved high-fidelity two-qubit gates resilient to experimental drifts.

Demonstrated rapid gate execution with effective Rabi frequency near detuning.

Enabled scalable quantum computing with long ion chains.

Abstract

Two-qubit gate performance is vital for scaling up ion-trap quantum computing. Optimized quantum control is needed to achieve reductions in gate-time and gate error-rate. We describe two-qubit gates with addressed Raman beams within a linear trapped-ion chain by a quantum master equation (QME). The QME incorporates the single-ion two-photon effective Rabi frequency, Autler-Townes and vibrational Bloch-Siegert energy shifts, off-resonant transitions, Raman and Rayleigh scattering, laser-power fluctuations, motional heating, cross-Kerr phonon coupling, laser spillover, asymmetric addressing beams and an imperfect initial motional ground state, with no fitting parameters. Whereas state-of-the-art methods are oblivious to these effects in the gate design procedure. We employ global optimization to design pulse sequences for achieving a robust rapid two-qubit gate for seven trapped $^{171}$Yb$^{+}$ ions by optimizing over numerically integrated QME solutions. Here, robust means resilient against slow drift of motional frequencies, and rapid means gate execution where the effective Rabi frequency is comparable to the detuning of the laser from the ion's bare electronic transition. Our robust quantum control delivers rapid high-quality two-qubit gates in long ion chains, enabling scalable quantum computing with trapped ions.