  We propose a method to construct quantum storage wherein the phase error due
to decoherence is naturally suppressed without constant error detection and
correction. As an example, we describe a quantum memory made of two physical
qubits encoded in the ground state of a two-qubit phase-error detecting code.
Such a system can be simulated by introducing a coupling between the two
physical qubits. This method is effective for physical systems in which the
$T_1$ decay process is negligible but coherence is limited by the $T_2$ decay
process. We take trapped ions as a possible example to apply the natural
suppression method and show that the $T_2$ decay time due to slow ambient
fluctuating fields at the physical qubits can be lengthened as much as $10^4$.
