d-Mon: A Transmon with Strong Anharmonicity Based on Planar c-Axis Tunneling Junction between d-Wave and s-Wave...

Area of Science:

• Quantum computing
• Condensed matter physics
• Superconductivity

Background:

• Superconducting qubits are crucial for quantum computation.
• Existing qubit designs face challenges with coherence times and tunability.
• D-wave superconductors offer unique electronic properties but are difficult to integrate into qubits.

Purpose of the Study:

• To propose a novel qubit architecture, the "d mon", utilizing a d-wave superconductor.
• To achieve insensitivity to charge fluctuations and tunable anharmonicity.
• To enable long coherence times by operating in a fully gapped quasiparticle regime.

Main Methods:

• Fabrication of a Josephson junction between a d-wave superconductor (Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$) and an s-wave superconductor.
• Operation of the device in the transmon regime.
• Tuning of the energy level spectrum via device geometry and magnetic flux.

Main Results:

• The "d mon" qubit demonstrates insensitivity to offset charge fluctuations.
• Strong and widely tunable anharmonicity in the qubit's energy spectrum.
• Operation in a regime where quasiparticles are fully gapped, promising long coherence.

Conclusions:

• The proposed "d mon" qubit architecture is a promising candidate for scalable quantum computing.
• This design overcomes key limitations of previous superconducting qubits.
• The use of d-wave superconductors in this configuration opens new avenues for qubit development.