1
|
Amies-King B, Schatz KP, Duan H, Biswas A, Bailey J, Felvinti A, Winward J, Dixon M, Minder M, Kumar R, Albosh S, Lucamarini M. Quantum Communications Feasibility Tests over a UK-Ireland 224 km Undersea Link. ENTROPY (BASEL, SWITZERLAND) 2023; 25:1572. [PMID: 38136452 PMCID: PMC10743312 DOI: 10.3390/e25121572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 10/27/2023] [Accepted: 11/14/2023] [Indexed: 12/24/2023]
Abstract
The future quantum internet will leverage existing communication infrastructures, including deployed optical fibre networks, to enable novel applications that outperform current information technology. In this scenario, we perform a feasibility study of quantum communications over an industrial 224 km submarine optical fibre link deployed between Southport in the United Kingdom (UK) and Portrane in the Republic of Ireland (IE). With a characterisation of phase drift, polarisation stability and the arrival time of entangled photons, we demonstrate the suitability of the link to enable international UK-IE quantum communications for the first time.
Collapse
Affiliation(s)
- Ben Amies-King
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Karolina P. Schatz
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Haofan Duan
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Ayan Biswas
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Jack Bailey
- euNetworks Fiber UK Limited, 5 Churchill Place, London E14 5HU, UK
| | - Adrian Felvinti
- euNetworks Fiber UK Limited, 5 Churchill Place, London E14 5HU, UK
| | - Jaimes Winward
- euNetworks Fiber UK Limited, 5 Churchill Place, London E14 5HU, UK
| | - Mike Dixon
- euNetworks Fiber UK Limited, 5 Churchill Place, London E14 5HU, UK
| | - Mariella Minder
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol 3036, Cyprus
| | - Rupesh Kumar
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Sophie Albosh
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| | - Marco Lucamarini
- School of Physics, Engineering & Technology and York Centre for Quantum Technologies, Institute for Safe Autonomy, University of York, York YO10 5FT, UK
| |
Collapse
|
2
|
Berra F, Agnesi C, Stanco A, Avesani M, Kuklewski M, Matter D, Vallone G, Villoresi P. Synchronization of quantum communications over an optical classical communications channel. APPLIED OPTICS 2023; 62:7994-7999. [PMID: 38038093 DOI: 10.1364/ao.500416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 10/01/2023] [Indexed: 12/02/2023]
Abstract
Precise synchronization between a transmitter and receiver is crucial for quantum communications protocols such as quantum key distribution (QKD) to efficiently correlate the transmitted and received signals and increase the signal-to-noise ratio. In this work, we introduce a synchronization technique that exploits a co-propagating classical optical communications link and tests its performance in a free-space QKD system. Previously, existing techniques required additional laser beams or relied on the capability to retrieve the synchronization from the quantum signal itself; this approach, however, is not applicable in high channel loss scenarios. On the contrary, our method exploits classical and quantum signals locked to the same master clock, allowing the receiver to synchronize both the classical and quantum communications links by performing a clock-data-recovery routine on the classical signal. In this way, by exploiting the same classical communications already required for post-processing and key generation, no additional hardware is required, and the synchronization can be reconstructed from a high-power signal. Our approach is suitable for both satellite and fiber infrastructures, where a classical and quantum channel can be transmitted through the same link.
Collapse
|
3
|
Zheng XT, Zhang QF, Han JY, Ling J, Guo GC, Han ZF. Experimental realization of free-space continuous-variable quantum key distribution based on fiber Sagnac interferometer. OPTICS LETTERS 2023; 48:4837-4840. [PMID: 37707915 DOI: 10.1364/ol.502897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 08/23/2023] [Indexed: 09/15/2023]
Abstract
The Gaussian-modulated coherent state (GMCS) is a well-known continuous-variable quantum key distribution (CV-QKD) protocol that is robust to incoherent background noise and can effectively suppress ambient light in free space. However, it is difficult to implement this protocol in free space using existing polarization coding schemes. In this Letter, we propose a polarization coding structure based on a self-compensating fiber Sagnac interferometer, which can reduce the required modulation voltage by two orders of magnitude and achieve fast and arbitrary polarization modulation, and experimentally demonstrate polarization coding-based GMCS CV-QKD for, it is believed, the first time. The proposed polarization modulation structure, which uses off-the-shelf fiber components, is compact, simple, and suitable for mobile terminals, such as flying lifts.
Collapse
|
4
|
Stein A, López Grande IH, Castelvero L, Pruneri V. Robust polarization state generation for long-range quantum key distribution. OPTICS EXPRESS 2023; 31:13700-13707. [PMID: 37157252 DOI: 10.1364/oe.481797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We present a new compact and robust polarization state transmitter designed to execute the BB84 quantum key distribution protocol. Our transmitter prepares polarization states using a single commercial-off-the-shelf phase modulator. Our scheme does not require global biasing to compensate thermal and mechanical drifts, as both of the system's two time-demultiplexed polarization modes share a single optical path. Furthermore, the transmitter's optical path entails a double-pass through the phase modulation device for each polarization mode, allowing multiple phase rotations to be impinged on each light pulse. We present a proof-of-concept prototype of this transmitter topology and demonstrate a mean intrinsic quantum bit error rate below 0.2% over a 5 hour measurement.
Collapse
|
5
|
Noblet Y, Donaldson R. BB84 quantum key distribution transmitter utilising broadband sources and a narrow spectral filter. OPTICS EXPRESS 2023; 31:15145-15155. [PMID: 37157362 DOI: 10.1364/oe.487424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The secure nature of Quantum Key Distribution (QKD) protocols makes it necessary to ensure that the single photon sources are indistinguishable. Any spectral, temporal or spatial discrepancy between the sources would lead to a breach in the security proofs of the QKD protocols. Traditional, weak-coherent pulse implementations of polarization-based QKD protocols have relied on identical photon sources obtained through tight temperature control and spectral filtering. However, it can be challenging to keep the temperature of the sources stable over time, particularly in a real-world setting, meaning photon sources can become distinguishable. In this work, we present an experimental demonstration of a QKD system capable of achieving spectral indistinguishability, over a 10°C range, using a combination of broadband sources, super-luminescent light emitting diodes (SLEDs), along with a narrow band-pass filter. The temperature stability could be useful in a satellite implementation, where there may be temperature gradients over the payload, particularly on a CubeSat.
Collapse
|
6
|
Avesani M, Calderaro L, Foletto G, Agnesi C, Picciariello F, Santagiustina FBL, Scriminich A, Stanco A, Vedovato F, Zahidy M, Vallone G, Villoresi P. Resource-effective quantum key distribution: a field trial in Padua city center. OPTICS LETTERS 2021; 46:2848-2851. [PMID: 34129556 DOI: 10.1364/ol.422890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/28/2021] [Indexed: 06/12/2023]
Abstract
Field trials are of key importance for novel technologies seeking commercialization and widespread adoption. This is also the case for quantum key distribution (QKD), which allows distant parties to distill a secret key with unconditional security. Typically, QKD demonstrations over urban infrastructures require complex stabilization and synchronization systems to maintain a low quantum bit error and high secret key rates over time. Here we present a field trial that exploits low-complexity self-stabilized hardware and a novel synchronization technique, to perform QKD over optical fibers deployed in the city center of Padua, Italy. Two techniques recently introduced by our research group are evaluated in a real-world environment: the iPOGNAC polarization encoder was used for preparation of the quantum states, while temporal synchronization was performed with the Qubit4Sync algorithm. The results here presented demonstrate the validity and robustness of our resource-effective QKD system, which can be easily and rapidly installed in an existing telecommunication infrastructure, thus representing an important step towards mature, efficient, and low-cost QKD systems.
Collapse
|