Abstract
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 decay process is negligible but coherence is limited by the decay process. We take trapped ions as a possible example to apply the natural suppression method and show that the decay time due to slow ambient fluctuating fields at the physical qubits can be lengthened as much as .