An ultra-high gain single-photon transistor in the microwave regime*

Photon-photon interaction at the single-photon level enables the realization of a single-photon transistor, in analogy to an electronic transistor, that can switch or amplify "source" photons controlled by a single "gate" photon. Circuit quantum electrodynamics provides great flexibility to generate such an interaction, and thus could serve as an effective platform to realize a high performance single-photon transistor. In this presentation, we will present our approach to the realization of such a photonic transistor in the microwave regime with circuit QED architectures, which consists of two microwave cavities dispersively coupled to a superconducting qubit. A single gate photon imprints a phase shift on the qubit state through one cavity as a controlled-phase gate, and further shifts the resonance frequency of the other cavity to trigger the switch of the input signal.

In this way, we realize a gain of the transistor up to 53.4 dB, with an extinction ratio better than 20 dB. Our device outperforms previous devices in the optical regime by several orders in terms of optical gain, which indicates a great potential for application in the field of microwave quantum photonics, such as coherent state manipulation and the realization of hardware-efficient quantum random access memory.