Daniel Campbell

Noise-Aware Entanglement Generation Protocols for Superconducting Qubits with Impedance-Matched FBAR Transducers

  1. Erin Sheridan,
  2. Michael Senatore,
  3. Samuel Schwab,
  4. Eric Aspling,
  5. Taylor Wagner,
  6. James Schneeloch,
  7. Stephen McCoy,
  8. Daniel Campbell,
  9. David Hucul,
  10. Zachary Smith,
  11. and Matthew LaHaye
Connecting superconducting quantum processors to telecommunications-wavelength quantum networks is critically necessary to enable distributed quantum computing, secure communications,
and other applications. Optically-mediated entanglement heralding protocols offer a near-term solution that can succeed with imperfect components, including sub-unity efficiency microwave-optical quantum transducers. The viability and performance of these protocols relies heavily on the properties of the transducers used: the conversion efficiency, resonator lifetimes, and added noise in the transducer directly influence the achievable entanglement generation rate and fidelity of an entanglement generation protocol. Here, we use an extended Butterworth-van Dyke (BVD) model to optimize the conversion efficiency and added noise of a Thin Film Bulk Acoustic Resonator (FBAR) piezo-optomechanical transducer. We use the outputs from this model to calculate the fidelity of one-photon and two-photon entanglement heralding protocols in a variety of operating regimes. For transducers with matching circuits designed to either minimize the added noise or maximize conversion efficiency, we theoretically estimate that entanglement generation rates of greater than 160kHz can be achieved at moderate pump powers with fidelities of >90%. This is the first time a BVD equivalent circuit model is used to both optimize the performance of an FBAR transducer and to directly inform the design and implementation of an entanglement generation protocol. These results can be applied in the near term to realize quantum networks of superconducting qubits with realistic experimental parameters.
arxiv pdf

Generating Spatially Entangled Itinerant Photons with Waveguide Quantum Electrodynamics

  1. Bharath Kannan,
  2. Daniel Campbell,
  3. Francisca Vasconcelos,
  4. Roni Winik,
  5. David Kim,
  6. Morten Kjaergaard,
  7. Philip Krantz,
  8. Alexander Melville,
  9. Bethany M. Niedzielski,
  10. Jonilyn Yoder,
  11. Terry P. Orlando,
  12. Simon Gustavsson,
  13. and William D. Oliver
Realizing a fully connected network of quantum processors requires the ability to distribute quantum entanglement. For distant processing nodes, this can be achieved by generating,
routing, and capturing spatially entangled itinerant photons. In this work, we demonstrate deterministic generation of such photons using superconducting transmon qubits that are directly coupled to a waveguide. In particular, we generate two-photon N00N states and show that the state and spatial entanglement of the emitted photons can be tuned via the qubit frequencies. Using quadrature amplitude detection, we reconstruct the moments and correlations of the photonic modes and demonstrate state preparation fidelities of 84%. Our results provide a path towards realizing quantum communication and teleportation protocols using non-classical, spatially entangled itinerant photons.
arxiv pdf