Novel Approaches to Error Detection and Protection with Superconducting Qubits

Introduction

Superconducting qubits have emerged as a leading platform for realizing intermediate- and large-scale quantum computing and quantum simulation. This success has been due to the exceedingly wide range of qubit encodings and rich physics attainable by combining superconducting circuit elements to achieve high coherence qubits and high fidelity quantum operations.

Project Objectives

In this project, I will demonstrate novel approaches to two central aspects of the future of superconducting quantum computing:

1. Despite the dramatic scaling in the number of qubits, the fundamental workhorse to implementing quantum algorithms and quantum error correction is still two-qubit interactions.
2. There has recently been a large interest in novel so-called 'protected qubit encodings' for high coherence, but none have yet been competitive with standard 'non-protected' qubits.

Main Results

The main results of NovaDePro will be:

• Implementation of a novel qubit-qubit coupling mechanism enabling fast microwave-activated multi-qubit gates.
• Demonstration of the first single-shot high-fidelity four-qubit gate and parity readout, enabled by the new coupling technique, in a surface code quantum error correction layout.
• A new approach to hybrid superconductor/semiconductor Josephson junctions with high stability (as demonstrated in our recent experiments) and coherence properties compatible with state-of-the-art superconducting qubits.
• The first demonstration of superconducting circuits that combine standard insulator-based and hybrid superconductor/semiconductor-based Josephson junctions to implement new high-coherence protected qubit encodings and straightforward quantum control schemes.

Conclusion

These achievements will push the boundaries of superconducting quantum computing by opening a new path for high-fidelity error correction in intermediate- and large-scale quantum computing and demonstrate a new family of high coherence protected qubits in a first-of-its-kind hybrid quantum circuit.