Generating multi-photon entangled state in a scalable way

Wan Li Yang, Hua Wei, Fei Zhou +1 more

Following a recent proposal (Devitt et al 2007 Phys. Rev. A 76 052312), we study the application of photonic modules on quantum information processing. We show how to generate various entangled states of atoms in a scalable way. In addition, we design two-qubit controlled-phase gating (CPhase) using photonic modules with the qubits encoded in either the photonic polarization or the atomic levels.

秀治 三上

Eisenberg, Bouwmester

Stefania Sciara, Piotr Roztocki, Bennet Fischer +9 more

Abstract Multi‐level (qudit) entangled photon states are a key resource for both fundamental physics and advanced applied science, as they can significantly boost the capabilities of novel technologies such as quantum communications, cryptography, sensing, metrology, and computing. The benefits of using photons for advanced applications draw on their unique properties: photons can propagate over long distances while preserving state coherence, and they possess multiple degrees of freedom (such as time and frequency) that allow scalable access to higher dimensional state encoding, all while maintaining low platform footprint and complexity. In the context of out‐of‐lab use, photon generation and processing through integrated devices and off‐the‐shelf components are in high demand. Similarly, multi‐level entanglement detection must be experimentally practical, i.e., ideally requiring feasible single‐qudit projections and high noise tolerance. Here, we focus on multi‐level optical Bell and cluster states as a critical resource for quantum technologies, as well as on universal witness operators for their feasible detection and entanglement characterization. Time‐ and frequency‐entangled states are the main platform considered in this context. We review a promising approach for the scalable, cost‐effective generation and processing of these states by using integrated quantum frequency combs and fiber‐based devices, respectively. We finally report an experimentally practical entanglement identification and characterization technique based on witness operators that is valid for any complex photon state and provides a good compromise between experimental feasibility and noise robustness. The results reported here can pave the way toward boosting the implementation of quantum technologies in integrated and widely accessible photonic platforms.

I. Afek, O. Ambar, Y. Siberberg

We experimentally realize a scheme for generation of maximally path entangled multi-photon states. Sub-wavelength Mach-Zehnder interference is measured for two, three and four photons. The results are simply scalable to higher numbers.

Harald Weinfurter