Quantum-information encoding in dressed qubits

It is shown that quantum information stored in a two-level system coupled to a super-Ohmic bosonic bath is coherently distributed between the system and the environment. A different two-level subsystem, including a proper coherent state of the environment, satisfies all control, reset, and measurement conditions required for a qubit, including two-qubit conditional gates. Such a dressed qubit is decoupled from the remaining environmental degrees of freedom but its control imposes specific adiabaticity conditions. The dressed qubit is the actual physical medium in which quantum information is encoded whenever control operations are slower than the environment dynamics.