Atheism is not materialism. I am an atheist but I am NOT a materialist.
Quantum mind is energy, energy that is manifested as consciousness, thoughts, feelings and perceptions. This energy can persist as quantum information or what we call memories.
If you believe that consciousness, thoughts, feelings and perceptions are energy that can persist as memories, that's all you need. In fact, each living day of ours is a mini past life. Yesterday was a mini past life. The day before was a mini past life. Each day you wake up is always a new you. You are never the same as yesterday. Your thoughts changes, your feelings changes, your perceptions changes, your body changes, your consciousness changes.
Tell me, which part of you is not subject to change? Your body, or your consciousness, or your thoughts, or your feelings, or your perceptions? Is there anything about the soul that cannot be described by the body, or consciousness, or thoughts, or feelings, or perceptions?