Ulysse Reglade – Quantum control of a cat qubit exhibiting switching times exceeding ten seconds

Описание: Macroscopic switching times between two stable states are widespread in science and engineering. Common examples are the reversal of earth’s magnetic field, or bit-flips in computer memories. Remarkably, long switching times persist even in systems at wildly reduced scales, such as oscillators containing only a handful of photons. Despite far reaching implications in quantum information science, preparing and measuring quantum superpositions of long-lived dynamical states has remained out of reach. Previous attempts achieved quantum control by introducing ancillary systems that in turn propagated errors limiting the switching times in the millisecond range. In this work, we implement a bistable dynamical system in a nonlinearly dissipative superconducting oscillator with an embedded parametric tool for quantum control and tomography. Through direct Wigner tomography, we observe quantum superpositions of dynamical states with switching times up to twenty seconds. Using quantum Zeno dynamics, we control the phase of these superpositions, and observe coherent oscillations decaying on the scale of hundreds of nanoseconds. This experiment demonstrates the encoding of quantum information in macroscopically stable dynamical states, promising shortcuts in the emergence of quantum technologies.