Cryogenic optical data link for superconducting circuits

Itay Shomroni, Amir Youssefi, Nathan Bernier +3 more

Caleb Howington, Alexander Opremcak, Alex F. Kirichenko +3 more

Oleg A. Mukhanov, I. V. Vernik, Alex F. Kirichenko +4 more

We develop an energy efficient digital data link connecting cryogenic superconducting single flux quantum (SFQ) circuits to room-temperature electronics. The design is based on low-temperature (4 K) superconductor ERSFQ SFQ/dc drivers, high-temperature superconductor data cables spanning 4 K to 70 K temperature stages, mid-temperature (70 K) polarization modulation vertical cavity surface emitting lasers (PM VCSELs), and fiber optic links to room temperature electronics. The Energy-efficient Cryogenic Optical (ECO) data link design is based on balancing power dissipation and signal gain at each temperature stage to maximize overall energy efficiency following the recently introduced Thermo-Gain Rule. To achieve VCSEL light emission with two switchable distinct polarization modes, a cruciform-shaped anisotropic optical cavity is formed by fabrication of a photonic crystal with etched periodic air holes surrounding the unetched cruciform region. In this report, we present the results of design, fabrication, and preliminary testing of the ECO data link components.

Paul Magnard, Simon Storz, Philipp Kurpiers +11 more

Superconducting circuits are a strong contender for realizing quantum computing systems and are also successfully used to study quantum optics and hybrid quantum systems. However, their cryogenic operation temperatures and the current lack of coherence-preserving microwave-to-optical conversion solutions have hindered the realization of superconducting quantum networks spanning different cryogenic systems or larger distances. Here, we report the successful operation of a cryogenic waveguide coherently linking transmon qubits located in two dilution refrigerators separated by a physical distance of five meters. We transfer qubit states and generate entanglement on demand with average transfer and target state fidelities of 85.8% and 79.5%, respectively, between the two nodes of this elementary network. Cryogenic microwave links provide an opportunity to scale up systems for quantum computing and create local area superconducting quantum communication networks over length scales of at least tens of meters.

Amir Youssefi, Itay Shomroni, Yash J. Joshi +5 more

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