Oct 27, 2021 |
Chip-based quantum microcomb creates entanglement between optical fields
(Nanowerk News) Researchers have developed a tiny optical frequency comb, or microcomb, that uses two-mode squeezing to create unconditional entanglement between continuous optical fields. The miniature chip-based device lays the groundwork for mass production of deterministic quantum frequency combs that could be used for quantum computing, quantum metrology and quantum sensing.
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Zijiao Yang from the University of Virginia, USA will present the research at the Frontiers in Optics + Laser Science Conference (FiO LS) all-virtual meeting, 01 – 04 November 2021. Yang’s presentation is scheduled for Tuesday, 02 November at 08:30 EDT (UTC – 04:00).
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The new microcomb is designed for quantum information protocols based on continuous-variable entangled states which generates entangled states, or qumodes, for entire optical fields rather than single photons. There is great interest in this protocol because, unlike qubit-based methods, there is no requirement for single photons or special optical modulation.
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“Unlike qubit approaches, continuous-variable approaches enable the number of entangled qumodes in a quantum state to be scaled up through frequency, time or spatial multiplexing without the need of quantum memory or the repeat-until-success strategies,” said Yang. “Our new microcomb could provide a scalable physical platform for continuous-variable quantum computing.”
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The new quantum microcomb is generated in a 3-millimeter-diameter silica wedge microresonator with a 22 GHz free spectral range on a silicon chip with a single mode tapered fiber used as the coupling waveguide. It uses two-mode squeezing to create unconditional entanglement between continuous optical fields.
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To test the new device, the researchers measured 20 qumode pairs created by the new microcomb. They found that the qumodes exhibited a maximum raw squeezing of 1.6 dB and maximum anti-squeezing of 6.5 dB. The raw squeezing is primarily limited by the 83% cavity escape efficiency, 1.7 dB optical loss and approximately 89% photodiode quantum efficiency.
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The researchers report a total efficiency after the tapered fiber of 60%. The squeezing measurements provide convincing evidence for quantum correlations among the qumodes, but the squeezing level needs to be further increased for quantum information processing applications.
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The researchers say that the raw squeezing could be improved by reducing system losses, improving photodiode quantum efficiency and achieving higher resonator-waveguide escape efficiency.
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