TY - JOUR

T1 - Scalable and effective multi-level entangled photon states

T2 - A promising tool to boost quantum technologies

AU - Sciara, Stefania

AU - Roztocki, Piotr

AU - Fischer, Bennet

AU - Reimer, Christian

AU - Romero Cortés, Luis

AU - Munro, William J.

AU - Moss, David J.

AU - Cino, Alfonso C.

AU - Caspani, Lucia

AU - Kues, Michael

AU - Azanã, José

AU - Morandotti, Roberto

N1 - Funding Information: This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Steacie, Strategic, Discovery, and Acceleration Grants Schemes, by the MESIPSR-SIIRI Initiative in Québec, by the Canada Research Chair Program, and by the Australian Research Council Discovery Projects scheme (DP1501104327). C. R. and P. R. acknowledge the support of NSERC Vanier Canada Graduate Scholarships. M. K. acknowledges support from the European Union’s Horizon 2020 Research and Innovation programme under the Marie Sklodowska-Curie grant agreement number 656607. W. J. M. acknowledges support from the John Templeton Foundation (JTF) number 60478. R.M. acknowledges additional support by the Professorship Program (grant 074-U 01) and from the 1000 Talents Sichuan Program. We thank R. Helsten for technical insights, and Quantum Opus and N. Bertone of OptoElectronics Components for their support and for providing us with state-of-the-art photon detection equipment.

PY - 2021/12

Y1 - 2021/12

N2 - 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- A nd 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.

AB - 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- A nd 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.

KW - complex entanglement

KW - experimentally feasible entanglement characterization

KW - integrated and cost-efficient photonic platforms

KW - photon cluster states

KW - quantum photonics

KW - witness operators

UR - http://www.scopus.com/inward/record.url?scp=85119407246&partnerID=8YFLogxK

U2 - 10.1515/nanoph-2021-0510

DO - 10.1515/nanoph-2021-0510

M3 - Review article

AN - SCOPUS:85119407246

VL - 10

SP - 4447

EP - 4465

JO - Nanophotonics

JF - Nanophotonics

SN - 2192-8606

IS - 18

ER -