Multimode photon blockade*

Strong interactions and the resulting correlations are responsible for much of the richness observed in quantum many body systems. We present a new non-local many-body interaction between microwave photons stored in the electromagnetic modes of a multimode cavity [1]. The microwave cavity features 9 modes with photon lifetimes of ~2 ms coupled to a superconducting transmon circuit, forming a multimode circuit QED system with single photon cooperativities of ~1 billion [2]. This multimode photon blockade interaction is similar to Coulomb blockade for electrons, but in this case acts on the total number of photons shared across a group of cavity modes. The system is dressed using cavity photon number resolved transmon drives such that there is collectively no interaction until a target total photon number is reached across multiple distinct modes, at which point they interact strongly. We harness the interaction for state preparation, preparing Fock states of increasing photon number via quantum optimal control pulses acting only on the cavity modes. We also use multimode photon blockade to generate entanglement only with uniform cavity drives, and characterize the resulting 2 and 3-mode W states using a new protocol for multimode Wigner tomography. These interactions are promising for studies of many body quantum optics, and for quantum information processing using multimode circuit QED.

[1] S. Chakram*, K. He*, A. Dixit, A. Oriani, R. Naik, N. Leung, H. Kwon, W.-L. Ma, L. Jiang, and D. Schuster, Multimode photon blockade, arXiv:2010.15292 (2020).
[2] S. Chakram*, A. Oriani*, R. Naik, A. Dixit, Kevin He, A.Agrawal, H.Kwon, and D. Schuster, Seamless monolithic high-Q microwave cavities for circuit quantum electrodynamics, arXiv:2010:16382 (2020)