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arXiv:2308.14173 · Physical Review Applied

Heralding entangled optical photons from a microwave quantum processor

Trond Hjerpekjøn Haug, Anton Frisk Kockum, Raphaël Van Laer

Published Sep 27, 2024• 6 citations
arXivHTMLPDF

Abstract

Exploiting the strengths of different quantum hardware components may increase the capabilities of emerging quantum processors. Here we propose and analyze a quantum architecture that leverages the nonlocal connectivity of optics, along with the exquisite quantum control offered by superconducting microwave circuits, to produce entangled optical resource states. In contrast to previous proposals on optically distributing entanglement between superconducting microwave processors, we use squeezing between microwaves and optics to produce microwave-optical Bell pairs in a dual-rail encoding from a single microwave quantum processor. Moreover, the microwave quantum processor allows us to deterministically entangle microwave-optical Bell pairs into larger cluster states, from which entangled optical photons can be extracted through microwave measurements. Our scheme paves the way for small microwave quantum processors to create heralded entangled optical resource states for optical quantum computation, communication, and sensing using imperfect microwave-optics transducers. We expect that improved isolation of the superconducting processor from stray optical fields will allow the scheme to be demonstrated with currently available hardware. Published by the American Physical Society 2024

DOI
10.1103/physrevapplied.22.034068

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A quantum network linking superconducting quantum computers would enable highly sought-after applications such as distributed quantum computing. Optical photons are the natural way of encoding information for long distance communication; however, exchanging quantum information between optical and microwave domains requires a quantum transducer. There are many ways transducers could be integrated into a network which leads to the question: Which network is most tolerant of current transducers which are far from perfect? A logical metric for optimizing the first quantum networks is the entanglement threshold which is necessary and sufficient condition on network parameters for microwave-microwave entanglement. Here we first address the problem of finding the network with the least restrictive entanglement threshold on physical parameters. For tractability we restrict our study to networks containing only gaussian states, operations, and measurements which are among the most readily experimentally accessible options. Within this vast space of possible network configurations, we identify a small set of topologies which we believe to be optimal. We find that with previously reported technology some of these topologies are capable of entangling remote microwave modes, despite imperfections in current transduction technology. Finally, progress towards a physical implementation of one of these topologies is discussed.