YSR Bond Qubit in a Double Quantum Dot with cQED Operation

Connecting two half-filled quantum dots to two superconducting leads induce a competetion of bonds, with the dots either forming an interdot exchange bond, or individual YSR screening bonds with the leads. Defining a qubit using these singlet parity bonding states yields both dot charge noise protection, due to the chargeless nature of the screening quasiparticles, and magnetic noise protection, as bonds protect against magnetic polarization. In this talk I propose to embed a DQD Josephson junction in parallel with a transmon to facilitate full cQED measurements and operation of a YSR bond qubit. I show that for realistic parameters two-tone spectroscopy of the DQD can be performed, and that a significant parameter regime is available for qubit operation. In addition, coherent manipulations of the bond states can be done via dot gates, and single-shot readout by measurements of a capacitively coupled resonator. Lastly, I show that gate noise on couplings are probably the primary source of qubit decoherence. As this qubit is protected against nuclear Overhauser fields and does not rely on spin-orbit interactions for operation a wider range of material platforms is available compared to current Andreev spin qubits, while qubit operations, measurement, and intialization can still be performed via cQED techniques.