Entropy- and purity-tailored broadband entanglement from vectorial four-wave mixing: Insights from pulse modes and classical-field dynamics

Abstract

We present a time-domain Schmidt-mode analysis of a broadband continuous-variable entanglement of photon pairs generated via a vectorial four-wave mixing (FWM) of ultrashort laser pulses in a highly nonlinear birefringent optical fiber. We demonstrate that the time-domain eigenmodes of high-purity two-photon states generated through vectorial FWM can be steered, by varying the pump wavelength and FWM polarization geometry, from a high-purity entangled ket to a high-entropy entangled state in a space of a very high dimensionality. Moreover, this pulse-mode analysis is shown to provide a clear physical perspective on how the entanglement structure of two-photon states builds up as a result of short-pulse FWM dynamics. This insight reveals a correspondence-type relation between the quantum and classical pictures of photon-pair generation. With an eye on practical applications, a clear understanding of the temporal profile of pulse modes representing highpurity two-photon states is central to a meaningful shaping of ultrashort photon-packet waveforms for super-resolving microscopy and multiphoton spectroscopy using quantum states of light.

Visible–Telecom Photon Pair Source Based on a Photonic-Crystal Fiber under Continuous-Wave Pumping

“…The most widespread modern methods for the generation of photon pairs are based on the use of spontaneous parametric down-conversion in crystals with a quadratic nonlinear susceptibility [13][14][15][16] and spontaneous four-wave mixing in optical fibers with cubic nonlinear susceptibility [17][18][19][20][21]. An important step toward the application of developed methods is the implementation of such sources on an optical platform ensuring their smallness and scalability.…”

Ultralow-power instant-on photon-pair counting and photon-entanglement analysis

“…The exosphere, however, presents a challenging environment for quantum communications due to prohibitive restrictions on the weight, size, and power requirements of satellite components needed for creating quantum relays. Recent advances in radiation tolerant detectors [6][7][8] and quantum photonics [9][10][11] have facilitated compact space-based single-photon detectors [12] for use in satellite quantum information systems, but further improvements to size, weight, and power requirements of the processing and analysis back-end of these detectors is possible with the advent of fast booting, low power field-programmable gate array (FPGA) processing solutions.…”