Quantum optical tunneling: A representation-free theory valid near the state-equation turning points

The problem of representation dependence in the treatment of quantum tunneling in absorptive optical bistability is considered. Disregarding this problem can lead to order-of-magnitude errors in calculated tunneling rates. A new description is presented, valid near the state-equation turning points, in which regime the discrepancies between different representations are shown to disappear. This description is also useful for treating critical fluctuations and dispersive cases.