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Conference on Lasers and Electro-Optics

A Quantum Light-Matter Beamsplitter in Diamond

Duncan G. England, Khabat Heshami, Philip J. Bustard, Benjamin Sussman, Kent Bonsma-Fisher, J. P. W. MacLean, Kevin J. Resch

Published Jan 1, 2017• 0 citations
Publisher

Abstract

A quantum memory can be viewed as a light-matter beam-splitter, mapping a photon to a superposition of the output optical mode and stored mode. We use this mechanism to demonstrate non-classical one-photon and two-photon interference.
DOI
10.1364/cleo_qels.2017.fm2e.5

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This thesis presents demonstrations of the storage and manipulation of single photons in \na room-temperature diamond quantum memory using a Raman memory protocol. We \nreport on results from four experiments. \n \nIn the first we demonstrate single photon storage and, upon retrieval, verify the quantum \nnature of the light with a Hanbury Brown Twiss measurement of g^(2)(0) = 0.65±0.07. \nA measurement of g^(2)(0) < 1 is indicative of quantum light. This is the first demonstration \nof single photon storage where the bandwidth of the stored light is greater than 1 THz. The \ndiamond memory stores light for over 13 times the duration of the input wavepacket. In \nthe second experiment, we report the storage and retrieval of polarization-encoded qubits \nand demonstrate qubit storage above a classical bound. We also verify that entanglement \nbetween the input photon and an auxiliary persists through storage and retrieval. \nWe then turn to additional uses of a Raman quantum memory. We demonstrate that \na photon stored in the diamond memory can, upon retrieval, have its frequency and bandwidth \nconverted. We report frequency conversion over a range of 4.2 times the bandwidth of \nthe input photon (4.1 nm, 2.3 THz), and bandwidth modulation between 0.5 to 1.9 times \nthe bandwidth of the input. We verify that the output light from storage and spectral \nmanipulation is still non-classical in nature. \n \nFinally, we demonstrate both single- and two-photon quantum interference mediated \nby the diamond memory, where the memory acts as a beamsplitter between photon and \noptical phonon modes in the diamond lattice. In a first experiment, a single photon is split \ninto two time-bins. The first time-bin is stored in the memory, then recalled and made to \ninterfere with the second time-bin producing fringes. In a second experiment, a photon \nfrom a weak coherent state is stored in the memory and, upon retrieval, undergoes Hong- \nOu-Mandel interference with a second photon. We measure Hong-Ou-Mandel interference \nwith a visibility of 59% giving a signature of non-classical interference (> 50%). \nThis collection of experiments establishes the diamond memory as a prime candidate for \ncertain quantum communication and processing applications. These results demonstrate \nthe potential for the diamond memory to be an integrated platform for photon storage, \nspectral conversion, and information processing.

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Two-photon interference effects arise because photons are indistinguishable particles. In the wellknown Hong-Ou-Mandel (HOM) effect, the transmission of two photons at a beam splitter interferes destructively with the reflection of both photons, requiring both photons to "bunch up" by leaving the beam splitter on the same side. Here, we show that the interference between locally propagating photons and photons exchanged by a mode swap can be implemented by post-selecting spatially separated photon outputs of a four-path interferometer. Even though the photons detected at spatially separated locations must have travelled along paths that never met up at the same beam splitter, the Hong-Ou-Mandel effect can be observed in correlations between the output ports that originate from the association of detection events with non-local output modes defined by the two single photon inputs. Local phase shifts can be used to map out non-classical correlations between the photons detected at different output locations, clarifying the role of linear optics in generating entanglement between spatially separated photons. Our work thus establishes a fundamental relation between multiphoton interference and entanglement, opening the door to new possibilities in optical quantum technologies.
This thesis presents demonstrations of the storage and manipulation of single photons in \na room-temperature diamond quantum memory using a Raman memory protocol. We \nreport on results from four experiments. \n \nIn the first we demonstrate single photon storage and, upon retrieval, verify the quantum \nnature of the light with a Hanbury Brown Twiss measurement of g^(2)(0) = 0.65±0.07. \nA measurement of g^(2)(0) < 1 is indicative of quantum light. This is the first demonstration \nof single photon storage where the bandwidth of the stored light is greater than 1 THz. The \ndiamond memory stores light for over 13 times the duration of the input wavepacket. In \nthe second experiment, we report the storage and retrieval of polarization-encoded qubits \nand demonstrate qubit storage above a classical bound. We also verify that entanglement \nbetween the input photon and an auxiliary persists through storage and retrieval. \nWe then turn to additional uses of a Raman quantum memory. We demonstrate that \na photon stored in the diamond memory can, upon retrieval, have its frequency and bandwidth \nconverted. We report frequency conversion over a range of 4.2 times the bandwidth of \nthe input photon (4.1 nm, 2.3 THz), and bandwidth modulation between 0.5 to 1.9 times \nthe bandwidth of the input. We verify that the output light from storage and spectral \nmanipulation is still non-classical in nature. \n \nFinally, we demonstrate both single- and two-photon quantum interference mediated \nby the diamond memory, where the memory acts as a beamsplitter between photon and \noptical phonon modes in the diamond lattice. In a first experiment, a single photon is split \ninto two time-bins. The first time-bin is stored in the memory, then recalled and made to \ninterfere with the second time-bin producing fringes. In a second experiment, a photon \nfrom a weak coherent state is stored in the memory and, upon retrieval, undergoes Hong- \nOu-Mandel interference with a second photon. We measure Hong-Ou-Mandel interference \nwith a visibility of 59% giving a signature of non-classical interference (> 50%). \nThis collection of experiments establishes the diamond memory as a prime candidate for \ncertain quantum communication and processing applications. These results demonstrate \nthe potential for the diamond memory to be an integrated platform for photon storage, \nspectral conversion, and information processing.