Coherently controlled storage of microwave pulse in superconducting artificial atoms

Quantum memory is necessary for synchronizing the information flow between distant qubits in large-scale quantum information processing. Coherent pulse control for quantum memory is experimentally advanced in the optical domain but nascent in microwave superconducting quantum circuits. Typical approach involves transferring microwave pulses between superconducting circuits and another media, e.g. nitrogen vacancy centers in diamond. However, such hybridization scheme leads to extra complexity in the fabrication process, and due to inhomogeneous broadening, the experimentally demonstrated storage time is only 30 ns. To avoid problems with hybridization, we propose to coherently store and retrieve on-demand a microwave pulse within a quantum circuit by exploiting existing electromagnetically induced transparency technology in quantum circuit. Our scheme employs a linear array of superconducting artificial atoms coupled to a microwave transmission line. When the control field is on, the artificial atomic medium becomes transparent to the input signal field and the signal pulse is longitudinally compressed as it enters the medium. Once the pulse is inside the medium, the control field is turned off to trap the pulse, and it is retrieved on-demand by turning on the control field again. As the medium is one-dimensional, the scattered field from each atom has reflection and transmission components and inter-atomic scattering interference can occur, but we show that the interference is not an issue to employ electromagnetically induced transparency for pulse storage. We predict that the storage efficiency of the pulse can reach 15% with just five artificial atoms in the medium and the efficiency increases asymptotically to near unity as the number of atoms increases. The surprisingly high efficiency suggests that coherent pulse storage with superconducting artificial atoms is a favorable approach for quantum memory in quantum circuits and a promising technology for quantum computing.