  It is a fundamental question that why quantum mechanics uses complex numbers
instead of only real numbers. To address this topic, recently, a rigorous
resource theory for the imaginarity of quantum states were established, and
several imaginarity measures were proposed. In this work, we propose a new
imaginarity measure based on the Tsallis relative entropy. This imaginarity
measure has explicit expression, and also, it is computable for bosonic
Gaussian states.
