Decoherence-Free Subspaces for Spontaneous Emission modeled by Continuous Spontaneous Localization*

Practical quantum information processing depends on long coherence times and fast and accurate quantum control. Understanding the boundaries of quantum system control is crucial to improving quantum processor design. One common challenge of quantum system control is the undetected spontaneous decay of excited states through spontaneous emission. The framework of continuous spontaneous localization can model spontaneous emission. Continuous spontaneous localization is a modification of quantum mechanics that addresses the measurement problem. It suggests that all particles have a constant and random localization process, which leads to an exponential suppression of superposition states with an increasing number of particles. This theory proposes that localization occurs continuously rather than due to a measurement or environmental interaction. In this study, we investigate the compatibility and realizability of decoherence-free subspaces to protect against spontaneous emission modeled by continuous spontaneous localization. Decoherence-free subspaces are quantum subspaces resistant to certain types of noise and decoherence, resulting in non-unitary dynamics due to system-bath couplings. By encoding quantum information in a decoherence-free subspace, the information can be protected from environmental disturbances and remain coherent for extended periods of time.