Interfacing Superconducting Qubits and Telecom Photons via a Rare-Earth-Doped Crystal

We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of $\pi$ pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered $\pi$ pulses. We predict total transfer efficiencies on the order of 90%.

Figure 1

Coherent and reversible transfer from telecom-wavelength photons to a superconducting qubit excitation can be achieved with rare-earth doped crystals coupled to a tunable superconducting cavity. Left: a single photon is absorbed into a collective spin excitation in the REDC. Right: the crystal spin is transferred into an excitation of the SCQ.

Figure 2

Transfer efficiency as a function of the intrinsic inhomogeneous broadening ${\delta }_{\mathrm{IB}}$ and the rephasing time ${\tau }_R$, for a fixed induced broadening of ${\delta }_{\text{inh}}=7G$ and $\kappa \sqrt{N}=6G$.

Figure 3

Numerical modeling of staggered transfer showing a 92% transfer, with an initial cavity detuning $\mathrm{\Delta }=20G$ and with $\kappa \sqrt{N}=6G$. With an intrinsic broadening of ${\delta }_{\mathrm{IB}}=2G$ and an induced broadening of ${\delta }_{\text{inh}}=10G$, which is completely compensated through rephasing of the symmetric Dicke state with an rephasing time of $G{\tau }_R=0.15$.