Abstract
Many technologies emerging from quantum information science heavily rely upon the generation and manipulation of entangled quantum states. Here, we propose and demonstrate a new class of quantum interference phenomena that arise when states are created in and coherently converted between the propagating modes of an optical microcavity. The modal coupling introduces several new creation pathways to a nonlinear optical process within the device, which quantum mechanically interfere to drive the system between states in the time domain. The coherent conversion entangles the generated biphotons between propagation pathways, leading to cyclically evolving path-entanglement and the manifestation of coherent oscillations in second-order temporal correlations. Furthermore, the rich device physics is harnessed to tune properties of the quantum states. In particular, we show that the strength of interference between pathways can be coherently controlled, allowing for manipulation of the degree of entanglement, which can even be entirely quenched. The states can likewise be made to flip-flop between exhibiting initially correlated or uncorrelated behavior. The phenomena presented here open a route to creating higher dimensional entanglement and exotic multi-photon states.
Highlights
Many technologies emerging from quantum information science heavily rely upon the generation and manipulation of entangled quantum states
We demonstrate that varying the cavity photon lifetime transforms the system from producing strongly entangled quantum states of light with extremely high-contrast two-photon interference visibility, to a regime where the entanglement and oscillations are quenched and the photon statistics return to the behavior of an uncoupled system
We implement the concept within a whispering-gallery mode (WGM) microresonator that supports spontaneous four-wave mixing (SFWM), a χ(3) nonlinear optical process[23], between three interacting cavity modes
Summary
Many technologies emerging from quantum information science heavily rely upon the generation and manipulation of entangled quantum states. A promising approach involves the quantum interference of multiple excitation/creation pathways, which coherently drives a system between states in the time domain These processes have led to a diverse set of important phenomena, including governing the dynamics of electron spins in semiconductors[18], many-body oscillations in cold atoms[19], superconducting flux qubits in Josephson junctions[20], inversionless laser oscillations in atomic media[21], and polarization entanglement between photon pairs emitted from biexcitons[22], to name a few. We propose and demonstrate a new class of quantum interference phenomena that result when quantum states are created in and coherently converted between propagating electromagnetic cavity modes We realize this concept by implementing a nonlinear optical process between the coupled counter-propagating modes of a microresonator—establishing multiple energy-level pathways for photon pair creation. The device may be configured to flexibly set the probability amplitudes associated with generating photon pairs in one or the other propagation modes, providing a means to explore how internal symmetry affects the quantum state and entanglement
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