Observation of Photon Blockade in a Tavis-Cummings System Using Photon Number Resolving Spectroscopy

Photon blockade, where absorption of one photon prevents further photon absorption is an important form of photon-photon interaction that has been investigated in many physical platforms. In Jaynes-Cummings systems, the presence of a two-level quantum emitter can induce a photon blockade in a coupled linear cavity, an effect that has been observed in atomic, quantum dot, and superconducting circuit systems. We present analogous results on observing photon blockade in a Tavis-Cummings system consisting of many superconducting transmons serving as quantum emitters coupled to a coplanar waveguide cavity. We demonstrate the presence of blockade with one, two, and three transmons resonantly coupled to the cavity using photon number resolving spectroscopy as a probe of the cavity photon number distribution. By varying the transmon-cavity detuning we show the crossover from approximately Poissonian cavity photon number statistics to the blockade regime where photon numbers greater than one are heavily suppressed.