Quantum information can be transferred from a beam of light to a cloud of atoms and controllably released at a later time. These quantum memory devices are fundamental to applications in quantum information science, quantum computing, and quantum communication. We propose a technique for measuring the quantum state of light that has been stored and released from a quantum memory system. This technique does not require careful mode matching can in fact be used to optimize the measured field mode without a priori knowledge of the stored light.
Andrew M. C. Dawes, Noah T. Holte, and Hunter A. Dassonville, "Quantum state tomography of slow and stored light," Proc. SPIE 8636, Advances in Slow and Fast Light VI, 863610 (2013) doi:10.1117/12.2010474.