  An optical quantum memory is a stationary device that is capable of storing
and recreating photonic qubits with a higher fidelity than any classical
device. Thus far, these two requirements have been fulfilled in systems based
on cold atoms and cryogenically cooled crystals. Here, we report a
room-temperature quantum memory capable of storing arbitrary polarization
qubits with a signal-to-background ratio higher than 1 and an average fidelity
clearly surpassing the classical limit for weak laser pulses containing 1.6
photons on average. Our results prove that a common vapor cell can reach the
low background noise levels necessary for quantum memory operation, and propels
atomic-vapor systems to a level of quantum functionality akin to other quantum
information processing architectures.
