Impact of leakage on the dynamics of a ST$_0$ qubit implemented in a Double Quantum Dot device

TL;DR

This paper investigates how leakage affects the phase and accuracy of spin qubit operations in double quantum dot devices, highlighting its implications for quantum computation and error mitigation.

Contribution

It demonstrates that leakage causes phase shifts in qubit evolution, offering insights into controlling leakage for improved quantum gate fidelity.

Findings

Leakage induces phase shifts in the evolution operator.

Controlling leakage can optimize gate times and coherence.

Leakage management benefits fault-tolerant quantum computing.

Abstract

Spin qubits in quantum dots are a promising technology for quantum computing due to their fast response time and long coherence times. An electromagnetic pulse is applied to the system for a specific duration to perform a desired rotation. To avoid decoherence, the amplitude and gate time must be highly accurate. In this work, we aim to study the impact of leakage during the gate time evolution of a spin qubit encoded in a double quantum dot device. We prove that, in the weak interaction regime, leakage introduces a shift in the phase of the time evolution operator, causing over- or under-rotations. Indeed, controlling the leakage terms is useful for adjusting the time needed to perform a quantum computation and increasing the coherence time of the readout process. This is crucial for running fault-tolerant algorithms and is beneficial for Quantum Error Mitigation techniques.