# Quantum dynamics of an electromagnetic mode that cannot contain N photons

When |
Jul 20, 2015
from 11:00 to 12:00 |
---|---|

Where | Centre Blaise Pascal |

Attendees |
Benjamin Huard |

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Electromagnetic modes are instrumental for realizing quantum physics experiments and building quantum machines. Their manipulation usually involves the tailoring of their Hamiltonian in time. An alternative control scheme, called Quantum Zeno Dynamics (QZD), consists in restricting the evolution of a mode to a subset of possible states. This promising control scheme has been implemented earlier this year on atomic levels of Rb and of a Rydberg atom. In this talk, I will report the first observation of QZD of light, using superconducting circuits [1]. By preventing the access to a single energy level, the dynamics of the field is dramatically changed. In this experiment, it was indeed possible to avoid a number of photons N, which was arbitrarily chosen between 2 and 5. Under this constraint, and starting in its ground state, a resonantly driven mode is confined to levels 0 to N-1. The level occupation is then found to oscillate in time, similarly to an N-level system. Performing a direct Wigner tomography of the field reveals its non-classical features. In particular, at half period in the evolution, it resembles a "Schrödinger cat state". All these observations are well captured by a model based on N levels only. Our results demonstrate that QZD allows the direct control of the field state in its phase space. This experiment paves the way to the realization of various protocols, such as phase space tweezers, generation and protection of entanglement, and quantum logic operations.

[1] Quantum dynamics of an electromagnetic mode that cannot contain N photons, L Bretheau, P Campagne-Ibarcq, E Flurin, F Mallet, B Huard, Science 348 (6236), 776 (2015)