Cécile Grezes

Flux Qubits in Three-Dimensional Circuit-QED Architecture

  1. Michael Stern,
  2. Yuimaru Kubo,
  3. Cecile Grezes,
  4. Audrey Bienfait,
  5. Denis Vion,
  6. Daniel Esteve,
  7. and Patrice Bertet
In this work, we present measurements of superconducting flux qubits embedded in a three dimensional copper cavity. The qubits were fabricated on a sapphire substrate and were measured
by coupling them inductively to an on-chip superconducting resonator located in the middle of the cavity. At their flux-insensitive point, all measured qubits reach an intrisic energy relaxation time comprised between 6 and 20 {\mu}s and a Ramsey dephasing time between 2 and 10 {\mu}s, a significant improvement over previous work.
arxiv pdf

Quantum memory for microwave photons in an inhomogeneously broadened spin ensemble

  1. Brian Julsgaard,
  2. Cécile Grezes,
  3. Patrice Bertet,
  4. and Klaus Mølmer
We propose a multi-mode quantum memory protocol able to store the quantum state of the field in a microwave resonator into an ensemble of electronic spins. The stored information is
protected against inhomogeneous broadening of the spin ensemble by spin-echo techniques resulting in memory times orders of magnitude longer than previously achieved. By calculating the evolution of the first and second moments of the spin-cavity system variables for realistic experimental parameters, we show that a memory based on NV center spins in diamond can store a qubit encoded on the |0> and |1> Fock states of the field with 80% fidelity.
arxiv pdf