Dartmouth Events

Abstract:  Quantum state transfer into a memory, state shuttling over long distances via a quantum bus, and high-fidelity readout are important tasks for quantum technology. Generating the Hamiltonians that realize these tasks is challenging in the presence of realistic couplings to an environment. Here, we use average Hamitlonian theory to design the desired Hamiltonians in cavity QED. In particular, we present a protocol for qubit-cavity state transfer. This approach makes use of a controllable qubit-cavity coupling to achieve a high fidelity even in the presence of inhomogeneous broadening that is stronger than the qubit-cavity coupling. With a small modification on the previous approach, we design a time-averaged interaction that allows for an improved quantum nondemolition readout. These ideas can be applied directly to novel systems coupling single spins to a microwave cavity [Viennot et al., Science 349, 408 (2015)]. This approach can also improve quantum operations with spin ensembles.