Spatiotemporal photon blockade for nonreciprocal quantum absorption

Abstract

Controlling the flow of electromagnetic energy is essential for advancing quantum technologies. We introduce a spatiotemporally modulated superconducting metasurface that exhibits photon-blockade-analogue nonreciprocal absorption. In this system, the frequency of incident radiation is matched to the modulation frequency of the metasurface, enabling one-way directional absorption. Forward-traveling waves undergo resonant coupling to higher-order Floquet harmonics and are absorbed within the slab, while backward-traveling waves transmit freely without interaction. This behavior arises from classical wave interference and harmonic conversion in a space-time periodic medium, a classical analogue of quantum photon blockade. We present a design based on a superconductor-semiconductor metasurface incorporating cascaded Josephson field-effect transistors (JoFETs) for millikelvin-temperature operation. Our analysis includes the system Hamiltonian, Floquet band structure, isofrequency diagrams, and full-wave simulations demonstrating strong nonreciprocal absorption. These findings establish a pathway toward compact, nonreciprocal superconducting devices for quantum information processing and microwave photonics.

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ORCID for Sajjad Taravati: orcid.org/0000-0003-3992-0050

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