Quantum optics without photons

Abhinav Kala, David Sharp, Minho Choi +7 more

Nonlinear interactions between photons are fundamentally weak as the photons do not interact directly with each other, and any interaction is mediated by matter. This has motivated researchers over many decades to search for strongly nonlinear materials (by controlling electronic properties) and optical resonators with strong spatial and temporal confinement of light. An extreme form of nonlinear optics is quantum nonlinear optics, where we can realize nonlinear interaction between single photons. Such quantum nonlinear optics is at the heart of any photonic quantum information system including analog quantum simulation and fault-tolerant quantum computing. While engineering light-matter interactions can effectively create photon-photon interactions, the required photon number to observe any nonlinearity are normally very high, where any quantum-mechanical signature disappears. However, with emerging low-dimensional materials and engineered photonic resonators, the photon number can be reduced to reach the quantum nonlinear optical regime. In this review paper, we discuss different mechanisms exploited in solid-state platforms to attain quantum nonlinear optics. We review emerging materials and optical resonator architectures with different dimensionalities. We also present future research directions and open problems in this field.

Vincenzo Macrí

F. E. Becerra

Christiana Varnava

Efficient conversion between microwave and optical photons is important for the development of hybrid quantum platforms in which quantum information is processed by superconducting circuits and transmitted with optical photons. A promising approach is to use electro-optic modulation with a microwave cavity coupled to an optical cavity, where microwave photons are up-converted to optical photons through sum frequency generation, and optical photons are converted to microwave photons through difference frequency generation. However, the frequency matching conditions in such set-ups usually require the size of the device to be large enough so that the optical frequencies of the pump and signal photons are supported. Hong Tang and colleagues have now fabricated a hybrid superconducting–photonic device that overcomes this limitation by using an integrated planar geometry to coherently convert between microwave and optical photons. adapted under a Creative Commons license CC BY-NC 4.0 ; AAAS

S. Chua

Kun Liao, Xiaoyong Hu, Tianyi Gan +7 more

Photonic molecules (PMs) are artificial nanoscale photonic structures that play important roles in the fundamental optics field. PM quantum optics has recently become a promising research field, because it provides novel quantum optical phenomena including Rabi oscillation, the Stark effect, the Purcell effect, the photon blockade effect, bound states in the continuum, electromagnetically induced transparency, and Autler–Townes splitting. With the constant improvements in theoretical PM quantum optics research, many newly integrated photonic devices have been proposed and experimentally demonstrated, showing major potential for fabrication of next-generation, high-performance integrated photonic chips. This review provides a universal overview of the rapidly developing PM quantum optics field, including fundamental mechanisms, realization frameworks, novel quantum optical phenomena, and applications in newly developed photonic devices while also giving a general summary of the remaining challenges and proposing possible development directions for PM quantum optics.