  Solid-state quantum emitters are vital building blocks for quantum
information science and quantum technology. Among various types of solid-state
emitters discovered to date, color centers in hexagonal boron nitride have
garnered tremendous traction in recent years thanks to their environmental
robustness, high brightness and room-temperature operation. Most recently,
these quantum emitters have been employed for satellite-based quantum key
distribution. One of the most important requirements to qualify these emitters
for space-based applications is their optical stability against cryogenic
thermal shock. Such understanding has, however, remained elusive to date. Here,
we report on the effects caused by such thermal shock which induces random,
irreversible changes in the spectral characteristics of the quantum emitters.
By employing a combination of structural characterizations and density
functional calculations, we attribute the observed changes to lattice strains
caused by the cryogenic temperature shock. Our study shed light on the
stability of the quantum emitters under extreme conditions, similar to those
countered in outer space.
