Experimental implementation of pair-cat code with superconducting microwave circuits(1/2)

Encoding quantum information in bosonic modes is a promising way to realize error-corrected logical qubits for fault tolerant quantum computing. In recent years there has been a lot of progress with qubits encoded in cat-states of single bosonic modes. However, existing experimental implementations of cat-states with superconducting circuits can only efficiently suppress one type of logical errors, either bit flips or phase flips. Interestingly, encoding quantum information on pair-cat states, which are superpositions of pair-coherent states of two bosonic modes, provides a promising pathway towards a fully error-corrected logical qubit. Driven-dissipative processes can stabilize a manifold of pair-cat states, providing exponential protection against phase-flip errors. Additionally, pair-cat code also allows for single photon loss detection in either mode, and hence the correction of bit flips, by monitoring the photon-number difference between them.  Advantageously, this error-syndrome can be continuously measured in a fault-tolerant manner without stopping manifold stabilization. Moreover, pair-cat code can lead to autonomously error-corrected logical qubits.

Part-one of this two-part presentation will introduce the design of the experimental apparatus, its tuning and calibration.