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Upper Bounds on Fidelity Preservation with Dynamical Decoupling

Michael Hsieh, University of Southern California

(Session 5 : Friday from 5:00-7:00)

Abstract. Dynamical decoupling (DD) continues to hold promise as a relatively simple but versatile means of mitigating the influence of a noisy and uncontrolled environment on a controlled quantum system. For a qubit coupled to a bath via an entangling Hamiltonian of the most general possible form, we calculate the range of possible joint qubit-bath dynamics (specifically, the set of permissible Kraus mappings for the total composite system) as a function of the parameters of the DD control pulses under a variety of DD pulse configurations. The upper bounds on system state fidelity preservation are obtained in terms of the minimal distance between the set of attainable Kraus mappings with the ideal set describing fully decoupled dynamics.

The Classically-Enhanced Father Protocol

Min-Hsiu Hsieh, Quantum Computation and Information Project, Solution Oriented Research for Science and Technology

(Session 12 : Sunday from 11:45-12:15)

Abstract. The classically-enhanced father protocol is an optimal protocol for a sender to transmit both classical and quantum information to a receiver by exploiting preshared entanglement and a large number of independent uses of a noisy quantum channel. We detail the proof of a quantum Shannon theorem that gives the three-dimensional capacity region containing all achievable rates that the classically-enhanced father protocol obtains. Points in the capacity region are rate triples consisting of the classical communication rate, the quantum communication rate, and the entanglement consumption rate of a particular coding scheme. The classically-enhanced father protocol is more general than any other protocol in the family tree of quantum Shannon theoretic protocols. Several previously known quantum protocols are now child protocols of the classically-enhanced father protocol. Interestingly, the classically-enhanced father protocol gives insight for constructing optimal classically-enhanced entanglement-assisted quantum error-correcting codes.