Accelerating qubit reset through the Mpemba effect

TL;DR

This paper introduces a protocol leveraging the Mpemba effect to significantly accelerate passive qubit reset times in quantum processors, demonstrating both theoretical robustness and experimental feasibility.

Contribution

It proposes a novel entangling gate-based protocol that exploits the Mpemba effect to speed up qubit relaxation, outperforming standard passive reset methods.

Findings

Reduces qubit reset time by up to 50%

Robust against non-Markovian noise and control imperfections

Successfully implemented on a superconducting quantum processor

Abstract

Passive qubit reset is a key primitive for quantum information processing, whereby qubits are initialized by allowing them to relax to their ground state through natural dissipation, without the need for active control or feedback. However, passive reset occurs on timescales that are much longer than those of gate operations and measurements, making it a significant bottleneck for algorithmic execution. Here, we show that this limitation can be overcome by exploiting the Mpemba effect, originally indicating the faster cooling of hot systems compared to cooler ones. Focusing on the regime where coherence times exceed energy relaxation times ($T_2 > T_1$), we propose a simple protocol based on a single entangling two-qubit gate that converts local single-qubit coherences into fast-decaying global two-qubit coherences. This removes their overlap with the slowest decaying Liouvillian mode and enables a substantially faster relaxation to the ground state. For realistic parameters, we find that our protocol can reduce reset times by up to $50\%$ compared to standard passive reset. We analyze the robustness of the protocol under non-Markovian noise, imperfect coherent control and finite temperature, finding that the accelerated reset persists across a broad range of realistic error sources. Finally, we present an experimental implementation of our protocol on an IQM superconducting quantum processor. Our results demonstrate how Mpemba-like accelerated relaxation can be harnessed as a practical tool for fast and accurate qubit initialization.