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arXiv:2104.05655 · Physical Review A

Spectrally resolved four-photon interference of time-frequency-entangled photons

Sofiane Merkouche, Valérian Thiel, Brian J. Smith

Published Feb 11, 2022• 7 citations
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Abstract

In this paper and an accompanying submission to $P\phantom{\rule{0}{0ex}}h\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ $R\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}w$ $L\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s$, the authors provide a demonstration of entanglement swapping extended into the multimode regime of ultrafast frequency-mode entanglement. The most salient feature of the method, which requires no source engineering, is the heralding of several mutually orthogonal Bell states derived from identical multimode entangled photon pairs.

DOI
10.1103/physreva.105.023708

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In this paper and an accompanying submission to P\phantom{\rule{0}{0ex}}h\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l R\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}w L\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s, the authors provide a demonstration of entanglement swapping extended into the multimode regime of ultrafast frequency-mode entanglement. The most salient feature of the method, which requires no source engineering, is the heralding of several mutually orthogonal Bell states derived from identical multimode entangled photon pairs.
Entanglement is a unique property of quantum systems and an essential resource for many quantum technologies. The ability to transfer or swap entanglement between systems is an important protocol in quantum information science. Entanglement swapping between photons forms the basis of distributed quantum networks. Here an experiment demonstrating entanglement swapping from two independent multimode time-frequency entangled sources is presented, resulting in multiple heralded frequency-mode Bell states. Entanglement in the heralded states is verified by measuring conditional anticorrelated joint spectra and quantum beating in two-photon interference. Our experiment heralds up to five orthogonal Bell pairs within the same setup, and this number is ultimately limited only by the entanglement of the initial sources.
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"Quantum communication is the art of transferring a quantum state from one place to another". The capability of distributing quantum states allows, for instance, provably secure communication and, in the near future, will enable the interconnection of quantum computers to establish a quantum internet. A convenient way to send quantum states from one place to another is to encode them into photons and distribute them using optical bres. The distance over which this can be achieved is still limited to a few hundred of kilometers. However, it can be extended in principle to arbitrary long distances by means of quantum repeaters. The realization of such quantum repeaters will require the engineering and interfacing of heterogeneous elements such as entangled photon-pair sources, quantum memories and entanglement swapping operations. The main goal of this thesis is to develop and study the compatibility of the main elements required to build a frequency multiplexed quantum repeater. This architecture requires a frequency multimode entangled photon pair source which, for example, could be implemented exploiting the process that involves the interaction of a strong light pulse with a non-linear crystal. Such a process is versatile and allows easy tailoring of the photon-pair spectral properties in order to match the requirements of the frequency multiplexed quantum repeater architecture. First, as a precursor of such a photon pair source, we developed a novel heralded single photon source that involves spectrally resolved single photon detection and on-demand frequency shifting. These capabilities are also essential tools in a frequency multiplexed quantum repeater. Next, we demonstrated the compatibility of such a sources with frequency multimode photonic quantum memories by performing spectrally multiplexed storage of single photons. We also tested the capability of high- delity storage of photons encoding quantum information in their polarization degree of freedom. Finally, we showed that entanglement swapping operations, i.e. Bell-state measurements, can be performed using photon pair sources compatible with quantum memories, quantum repeater architectures, and real-world scenarios. While a lot of e ort remains to be done, in the work presented in this thesis we demonstrated that all the key elements required to build a frequency multiplexed quantum repeater can be built and eventually be interfaced. The main obstacles towards that goal and possible ways to overcome them are also discussed.