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A fundamental challenge for quantum information processing is reducing the impact of environmentally-induced errors.Quantum error detection (QED) provides one approach to handling such errors, in which errors are rejected when they are detected.Here we demonstrate a QED protocol based on the idea of quantum un-collapsing, using this protocol to suppress energy relaxation due to the environment in a three-qubit superconducting circuit.We encode quantum information in a target qubit, and use the other two qubits to detect and reject errors caused by energy relaxation.This protocol improves the storage time of a quantum state by a factor of roughly three, at the cost of a reduced probability of success.This constitutes the first experimental demonstration of an algorithm-based improvement in the lifetime of a quantum state stored in a qubit.Using a similar protocol and a four-qubit superconducting circuit, we further demonstrate the protection of Bell-state entanglement against environmental dissipation.